addChildViewController:
removeFromParentViewController
transitionFromViewController:toViewController:duration:options:animations:completion:
willMoveToParentViewController:
didMoveToParentViewController:

[viewController.view addSubview:otherViewController.view]

[viewController.view addSubview:otherViewController.view]

[viewController addChildViewController:otherViewController]

[myObj performSelectorInBackground:@selector(doSomething) withObject:nil];

//
//  main.c
//  pthread
//
//  Created by Lu Kejin on 1/27/12.
//  Copyright (c) 2012 Taobao.com. All rights reserved.
//

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>

void *pthreadRoutine(void *);


int main (int argc, const char * argv[])
{
    pthread_attr_t  attr;
    pthread_t       pthreadID;
    int             returnVal;
    
    returnVal = pthread_attr_init(&attr);
    returnVal = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
    int threadError = pthread_create(&pthreadID, &attr, &pthreadRoutine, NULL);
    returnVal = pthread_attr_destroy(&attr);
    
    if (threadError != 0)
    {
        // Report an error.
    }
    
    sleep(10);
    
    return 0;
}


void *pthreadRoutine(void *data){
    int count = 0;
    while (1) {
        printf("count = %d\n",count++);
        sleep(1);
        
    }
    return NULL;
}

- (void)setMaxConcurrentOperationCount:(NSInteger)count

dispatch_queue_t imageDownloadQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    
dispatch_async(imageDownloadQueue, ^{
        NSURL *imageURL = [NSURL URLWithString:@"http://test.com/test.png"];
       NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
        UIImage *image = [UIImage imageWithData:imageData];
       dispatch_async(dispatch_get_main_queue(), ^{
            [imageView setImage:image];//UIKit必须在主线程执行
        });
    });

@interface NSObject (NSThreadPerformAdditions)

- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait modes:(NSArray *)array;
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait;
// equivalent to the first method with kCFRunLoopCommonModes

- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait modes:(NSArray *)array NS_AVAILABLE(10_5, 2_0);
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait NS_AVAILABLE(10_5, 2_0);
// equivalent to the first method with kCFRunLoopCommonModes
    ...
@end

enum CFRunLoopActivity {
   kCFRunLoopEntry = (1 << 0),
   kCFRunLoopBeforeTimers = (1 << 1),
   kCFRunLoopBeforeSources = (1 << 2),
   kCFRunLoopBeforeWaiting = (1 << 5),
   kCFRunLoopAfterWaiting = (1 << 6),
   kCFRunLoopExit = (1 << 7),
   kCFRunLoopAllActivities = 0x0FFFFFFFU
};
typedef enum CFRunLoopActivity CFRunLoopActivity;

netService = [[[NSNetService alloc] initWithDomain:@""
                                              type:@"_test._tcp"
                                              name:@""
                                              port:port] autorelease];
if(netService != nil) {
    [netService scheduleInRunLoop:[NSRunLoop currentRunLoop]
                               forMode:NSRunLoopCommonModes];
    netService.delegate = self;
    [netService publish];
}

testServiceBrowser = [[NSNetServiceBrowser alloc] init];
testServiceBrowser.delegate = self;
[testServiceBrowser searchForServicesOfType:@"_test._tcp" inDomain:@""];

//pragma mark NetServiceBroswer Delegate
- (void)netServiceBrowser:(NSNetServiceBrowser*)netServiceBrowser
           didFindService:(NSNetService*)service
                moreComing:(BOOL)moreComing {
   [netServiceArray addObject:service];
   if (!moreComing) {
       [serviceTableView reloadData];
   }
}

- (void)netServiceBrowser:(NSNetServiceBrowser*)netServiceBrowser
        didRemoveService:(NSNetService*)service
               moreComing:(BOOL)moreComing {
    [netServiceArray removeObject:service];
    if (!moreComing) {
        [serviceTableView reloadData];
    }
}

- (IBAction)connect:(id)sender{
    NSUInteger selectedRow = [serviceTableView selectedRow];
    NSNetService *selectedServiece = [netServiceArray objectAtIndex:selectedRow];
    selectedServiece.delegate = self;
    [selectedServiece resolveWithTimeout:5.0];
}

//NSNetService Delegate
- (void)netServiceDidResolveAddress:(NSNetService *)sender{
     NSLog(@"service ip:%@ port:%d",sender.address,sender.port);
    if ([sender getInputStream:&inputStream outputStream:&outputStream]) {
        [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                                         forMode:NSDefaultRunLoopMode];
        [outputStream open];
        //发送数据
        NSData *helloData = [@"Hello" dataUsingEncoding:NSUTF8StringEncoding];
        [outputStream write:[helloData bytes] maxLength:[helloData length]];
    }
}

#define     STDIN_FILENO   0   /* standard input file descriptor */
#define    STDOUT_FILENO   1   /* standard output file descriptor */
#define    STDERR_FILENO   2   /* standard error file descriptor */   

/*
* [XSI] Structure used by kernel to store most addresses.
*/
struct sockaddr {
    __uint8_t    sa_len;       /* total length */
    sa_family_t  sa_family;    /* [XSI] address family */
    char        sa_data[14];   /* [XSI] addr value (actually larger) */
};

/*
 * Socket address, internet style.
 */
struct sockaddr_in {
    __uint8_t    sin_len;
    sa_family_t  sin_family;
    in_port_t    sin_port;//得是网络字节序
    struct   in_addr sin_addr;//in_addr存在的原因则是历史原因，其实质是代表一个IP地址的32位整数
    char        sin_zero[8];//bzero之，纯粹是为了兼容sockaddr
};

#define ntohs(x)   __DARWIN_OSSwapInt16(x) // 16位整数 网络字节序转主机字节序
#define htons(x)   __DARWIN_OSSwapInt16(x) // 16位整数 主机字节序转网络字节序

#define ntohl(x)   __DARWIN_OSSwapInt32(x)  //32位整数 网络字节序转主机字节序
#define htonl(x)   __DARWIN_OSSwapInt32(x) //32位整数 主机字节序转网络字节序

#include <stdio.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>

int main (int argc, const char * argv[])
{
    struct sockaddr_in server_addr;
    server_addr.sin_len = sizeof(struct sockaddr_in);
    server_addr.sin_family = AF_INET;//Address families AF_INET互联网地址簇
    server_addr.sin_port = htons(11332);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    bzero(&(server_addr.sin_zero),8);
    
    //创建socket
    int server_socket = socket(AF_INET, SOCK_STREAM, 0);//SOCK_STREAM 有连接
    if (server_socket == -1) {
        perror("socket error");
        return 1;
    }
    
    //绑定socket：将创建的socket绑定到本地的IP地址和端口，此socket是半相关的，只是负责侦听客户端的连接请求，并不能用于和客户端通信
    int bind_result = bind(server_socket, (struct sockaddr *)&server_addr, sizeof(server_addr));
    if (bind_result == -1) {
        perror("bind error");
        return 1;
    }
    
    //listen侦听 第一个参数是套接字，第二个参数为等待接受的连接的队列的大小，在connect请求过来的时候,完成三次握手后先将连接放到这个队列中，直到被accept处理。如果这个队列满了，且有新的连接的时候，对方可能会收到出错信息。
    if (listen(server_socket, 5) == -1) {
        perror("listen error");
        return 1;
    }

    struct sockaddr_in client_address;
    socklen_t address_len;
    int client_socket = accept(server_socket, (struct sockaddr *)&client_address, &address_len);
    //返回的client_socket为一个全相关的socket，其中包含client的地址和端口信息，通过client_socket可以和客户端进行通信。
    if (client_socket == -1) {
        perror("accept error");
        return -1;
    }
    
    char recv_msg[1024];
    char reply_msg[1024];
    
    while (1) {
        bzero(recv_msg, 1024);
        bzero(reply_msg, 1024);
        
        printf("reply:");
        scanf("%s",reply_msg);
        send(client_socket, reply_msg, 1024, 0);
        
        long byte_num = recv(client_socket,recv_msg,1024,0);
        recv_msg[byte_num] = '\0';
        printf("client said:%s\n",recv_msg);

    }
    
    return 0;
}

#include <stdio.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>

int main (int argc, const char * argv[])
{
    struct sockaddr_in server_addr;
    server_addr.sin_len = sizeof(struct sockaddr_in);
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(11332);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    bzero(&(server_addr.sin_zero),8);
    
    int server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket == -1) {
        perror("socket error");
        return 1;
    }
    char recv_msg[1024];
    char reply_msg[1024];
    
    if (connect(server_socket, (struct sockaddr *)&server_addr, sizeof(struct sockaddr_in))==0)  {
    //connect 成功之后，其实系统将你创建的socket绑定到一个系统分配的端口上，且其为全相关，包含服务器端的信息，可以用来和服务器端进行通信。
        while (1) {
            bzero(recv_msg, 1024);
            bzero(reply_msg, 1024);
            long byte_num = recv(server_socket,recv_msg,1024,0);
            recv_msg[byte_num] = '\0';
            printf("server said:%s\n",recv_msg);
            
            printf("reply:");
            scanf("%s",reply_msg);
            if (send(server_socket, reply_msg, 1024, 0) == -1) {
                perror("send error");
            }
        }
        
    }
    
    // insert code here...
    printf("Hello, World!\n");
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#define BACKLOG 5 //完成三次握手但没有accept的队列的长度
#define CONCURRENT_MAX 8 //应用层同时可以处理的连接
#define SERVER_PORT 11332
#define BUFFER_SIZE 1024
#define QUIT_CMD ".quit"
int client_fds[CONCURRENT_MAX];
int main (int argc, const char * argv[])
{
    char input_msg[BUFFER_SIZE];
    char recv_msg[BUFFER_SIZE];   
    //本地地址
    struct sockaddr_in server_addr;
    server_addr.sin_len = sizeof(struct sockaddr_in);
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    bzero(&(server_addr.sin_zero),8);
    //创建socket
    int server_sock_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_sock_fd == -1) {
        perror("socket error");
        return 1;
    }
    //绑定socket
    int bind_result = bind(server_sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr));
    if (bind_result == -1) {
        perror("bind error");
        return 1;
    }
    //listen
    if (listen(server_sock_fd, BACKLOG) == -1) {
        perror("listen error");
        return 1;
    }
    //fd_set
    fd_set server_fd_set;
    int max_fd = -1;
    struct timeval tv;
    tv.tv_sec = 20;
    tv.tv_usec = 0;
    while (1) {
        FD_ZERO(&server_fd_set);
        //标准输入
        FD_SET(STDIN_FILENO, &server_fd_set);
        if (max_fd < STDIN_FILENO) {
            max_fd = STDIN_FILENO;
        }
        //服务器端socket
        FD_SET(server_sock_fd, &server_fd_set);
        if (max_fd < server_sock_fd) {
            max_fd = server_sock_fd;
        }
        //客户端连接
        for (int i = 0; i < CONCURRENT_MAX; i++) {
            if (client_fds[i]!=0) {
                FD_SET(client_fds[i], &server_fd_set);
                
                if (max_fd < client_fds[i]) {
                    max_fd = client_fds[i];
                }
            }
        }
        int ret = select(max_fd+1, &server_fd_set, NULL, NULL, &tv);
        if (ret < 0) {
            perror("select 出错\n");
            continue;
        }else if(ret == 0){
            printf("select 超时\n");
            continue;
        }else{
            //ret为未状态发生变化的文件描述符的个数
            if (FD_ISSET(STDIN_FILENO, &server_fd_set)) {
                //标准输入
                bzero(input_msg, BUFFER_SIZE);
                fgets(input_msg, BUFFER_SIZE, stdin);
                //输入 ".quit" 则退出服务器
                if (strcmp(input_msg, QUIT_CMD) == 0) {
                    exit(0);
                }
                for (int i=0; i<CONCURRENT_MAX; i++) {
                    if (client_fds[i]!=0) {
                        send(client_fds[i], input_msg, BUFFER_SIZE, 0);
                    }
                }
            }
            if (FD_ISSET(server_sock_fd, &server_fd_set)) {
                //有新的连接请求
                struct sockaddr_in client_address;
                socklen_t address_len;
                int client_socket_fd = accept(server_sock_fd, (struct sockaddr *)&client_address, &address_len);
                if (client_socket_fd > 0) {
                    int index = -1;
                    for (int i = 0; i < CONCURRENT_MAX; i++) {
                        if (client_fds[i] == 0) {
                            index = i;
                            client_fds[i] = client_socket_fd;
                            break;
                        }
                    }
                    if (index >= 0) {
                        printf("新客户端(%d)加入成功 %s:%d \n",index,inet_ntoa(client_address.sin_addr),ntohs(client_address.sin_port));
                    }else{
                        bzero(input_msg, BUFFER_SIZE);
                        strcpy(input_msg, "服务器加入的客户端数达到最大值,无法加入!\n");
                        send(client_socket_fd, input_msg, BUFFER_SIZE, 0);
                        printf("客户端连接数达到最大值，新客户端加入失败 %s:%d \n",inet_ntoa(client_address.sin_addr),ntohs(client_address.sin_port));
                    }
                }
            }
            for (int i = 0; i <CONCURRENT_MAX; i++) {
                if (client_fds[i]!=0) {
                    if (FD_ISSET(client_fds[i], &server_fd_set)) {
                        //处理某个客户端过来的消息
                        bzero(recv_msg, BUFFER_SIZE);
                        long byte_num = recv(client_fds[i],recv_msg,BUFFER_SIZE,0);
                        if (byte_num > 0) {
                            if (byte_num > BUFFER_SIZE) {
                                byte_num = BUFFER_SIZE;
                            }
                            recv_msg[byte_num] = '\0';
                            printf("客户端(%d):%s\n",i,recv_msg);
                        }else if(byte_num < 0){
                            printf("从客户端(%d)接受消息出错.\n",i);
                        }else{
                            FD_CLR(client_fds[i], &server_fd_set);
                            client_fds[i] = 0;
                            printf("客户端(%d)退出了\n",i);
                        }
                    }
                }
            }
        }
    }
    return 0;
}

#include <stdio.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

#define BUFFER_SIZE 1024

int main (int argc, const char * argv[])
{
    struct sockaddr_in server_addr;
    server_addr.sin_len = sizeof(struct sockaddr_in);
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(11332);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    bzero(&(server_addr.sin_zero),8);
    
    int server_sock_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_sock_fd == -1) {
        perror("socket error");
        return 1;
    }
    char recv_msg[BUFFER_SIZE];
    char input_msg[BUFFER_SIZE];
    
    if (connect(server_sock_fd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr_in))==0) {
        fd_set client_fd_set;
        struct timeval tv;
        tv.tv_sec = 20;
        tv.tv_usec = 0;

        
        while (1) {
            FD_ZERO(&client_fd_set);
            FD_SET(STDIN_FILENO, &client_fd_set);
            FD_SET(server_sock_fd, &client_fd_set);
            
            int ret = select(server_sock_fd + 1, &client_fd_set, NULL, NULL, &tv);
            if (ret < 0 ) {
                printf("select 出错!\n");
                continue;
            }else if(ret ==0){
                printf("select 超时!\n");
                continue;
            }else{
                if (FD_ISSET(STDIN_FILENO, &client_fd_set)) {
                    bzero(input_msg, BUFFER_SIZE);
                    fgets(input_msg, BUFFER_SIZE, stdin);
                    if (send(server_sock_fd, input_msg, BUFFER_SIZE, 0) == -1) {
                        perror("发送消息出错!\n");
                    }
                }
                
                if (FD_ISSET(server_sock_fd, &client_fd_set)) {
                    bzero(recv_msg, BUFFER_SIZE);
                    long byte_num = recv(server_sock_fd,recv_msg,BUFFER_SIZE,0);
                    if (byte_num > 0) {
                        if (byte_num > BUFFER_SIZE) {
                            byte_num = BUFFER_SIZE;
                        }
                        recv_msg[byte_num] = '\0';
                        printf("服务器:%s\n",recv_msg);
                    }else if(byte_num < 0){
                        printf("接受消息出错!\n");
                    }else{
                        printf("服务器端退出!\n");
                        exit(0);
                    }

                }
            }
        }
        
    }
    
    return 0;
}

   //sys/_structs.h
   #define __DARWIN_FD_SETSIZE 1024
   /////////////////////////////////////////////
   //Kernel.framework sys/select.h
   #define FD_SETSIZE  __DARWIN_FD_SETSIZE

#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/event.h>
#include <sys/types.h>
#include <sys/time.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#define BACKLOG 5 //完成三次握手但没有accept的队列的长度
#define CONCURRENT_MAX 8 //应用层同时可以处理的连接
#define SERVER_PORT 11332
#define BUFFER_SIZE 1024
#define QUIT_CMD ".quit"
int client_fds[CONCURRENT_MAX];
struct kevent events[10];//CONCURRENT_MAX + 2
int main (int argc, const char * argv[])
{
    char input_msg[BUFFER_SIZE];
    char recv_msg[BUFFER_SIZE];
    //本地地址
    struct sockaddr_in server_addr;
    server_addr.sin_len = sizeof(struct sockaddr_in);
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    bzero(&(server_addr.sin_zero),8);
    //创建socket
    int server_sock_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_sock_fd == -1) {
        perror("socket error");
        return 1;
    }
    //绑定socket
    int bind_result = bind(server_sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr));
    if (bind_result == -1) {
        perror("bind error");
        return 1;
    }
    //listen
    if (listen(server_sock_fd, BACKLOG) == -1) {
        perror("listen error");
        return 1;
    }
    struct timespec timeout = {10,0};
    //kqueue
    int kq = kqueue();
    if (kq == -1) {
        perror("创建kqueue出错!\n");
        exit(1);
    }
    struct kevent event_change;
    EV_SET(&event_change, STDIN_FILENO, EVFILT_READ, EV_ADD, 0, 0, NULL);
    kevent(kq, &event_change, 1, NULL, 0, NULL);
    EV_SET(&event_change, server_sock_fd, EVFILT_READ, EV_ADD, 0, 0, NULL);
    kevent(kq, &event_change, 1, NULL, 0, NULL);
    while (1) {
        int ret = kevent(kq, NULL, 0, events, 10, &timeout);
        if (ret < 0) {
            printf("kevent 出错!\n");
            continue;
        }else if(ret == 0){
            printf("kenvent 超时!\n");
            continue;
        }else{
            //ret > 0 返回事件放在events中
            for (int i = 0; i < ret; i++) {
                struct kevent current_event = events[i];
                //kevent中的ident就是文件描述符
                if (current_event.ident == STDIN_FILENO) {
                    //标准输入
                    bzero(input_msg, BUFFER_SIZE);
                    fgets(input_msg, BUFFER_SIZE, stdin);
                    //输入 ".quit" 则退出服务器
                    if (strcmp(input_msg, QUIT_CMD) == 0) {
                        exit(0);
                    }
                    for (int i=0; i<CONCURRENT_MAX; i++) {
                        if (client_fds[i]!=0) {
                            send(client_fds[i], input_msg, BUFFER_SIZE, 0);
                        }
                    }
                }else if(current_event.ident == server_sock_fd){
                    //有新的连接请求
                    struct sockaddr_in client_address;
                    socklen_t address_len;
                    int client_socket_fd = accept(server_sock_fd, (struct sockaddr *)&client_address, &address_len);
                    if (client_socket_fd > 0) {
                        int index = -1;
                        for (int i = 0; i < CONCURRENT_MAX; i++) {
                            if (client_fds[i] == 0) {
                                index = i;
                                client_fds[i] = client_socket_fd;
                                break;
                            }
                        }
                        if (index >= 0) {
                            EV_SET(&event_change, client_socket_fd, EVFILT_READ, EV_ADD, 0, 0, NULL);
                            kevent(kq, &event_change, 1, NULL, 0, NULL);
                            printf("新客户端(fd = %d)加入成功 %s:%d \n",client_socket_fd,inet_ntoa(client_address.sin_addr),ntohs(client_address.sin_port));
                        }else{
                            bzero(input_msg, BUFFER_SIZE);
                            strcpy(input_msg, "服务器加入的客户端数达到最大值,无法加入!\n");
                            send(client_socket_fd, input_msg, BUFFER_SIZE, 0);
                            printf("客户端连接数达到最大值，新客户端加入失败 %s:%d \n",inet_ntoa(client_address.sin_addr),ntohs(client_address.sin_port));
                        }
                    }
                }else{
                    //处理某个客户端过来的消息
                    bzero(recv_msg, BUFFER_SIZE);
                    long byte_num = recv((int)current_event.ident,recv_msg,BUFFER_SIZE,0);
                    if (byte_num > 0) {
                        if (byte_num > BUFFER_SIZE) {
                            byte_num = BUFFER_SIZE;
                        }
                        recv_msg[byte_num] = '\0';
                        printf("客户端(fd = %d):%s\n",(int)current_event.ident,recv_msg);
                    }else if(byte_num < 0){
                        printf("从客户端(fd = %d)接受消息出错.\n",(int)current_event.ident);
                    }else{
                        EV_SET(&event_change, current_event.ident, EVFILT_READ, EV_DELETE, 0, 0, NULL);
                        kevent(kq, &event_change, 1, NULL, 0, NULL);
                        close((int)current_event.ident);
                        for (int i = 0; i < CONCURRENT_MAX; i++) {
                            if (client_fds[i] == (int)current_event.ident) {
                                client_fds[i] = 0;
                                break;
                            }
                        }
                        printf("客户端(fd = %d)退出了\n",(int)current_event.ident);
                    }
                }
            }
        }
    }
    return 0;
}

- (BOOL)run:(NSError **)error{
    BOOL successful = YES;
    CFSocketContext socketCtxt = {0, self, NULL, NULL, NULL};
    _socket = CFSocketCreate(kCFAllocatorDefault, PF_INET, SOCK_STREAM, 
                             IPPROTO_TCP, 
                             kCFSocketAcceptCallBack,
                             (CFSocketCallBack)&SocketConnectionAcceptedCallBack,
                             &socketCtxt);
    if (NULL == _socket) {
        if (nil != error) {
            *error = [[NSError alloc] 
                      initWithDomain:ServerErrorDomain
                      code:kServerNoSocketsAvailable
                      userInfo:nil];
        }
        successful = NO;
    }
    if(YES == successful) {
        // enable address reuse
        int yes = 1;
        setsockopt(CFSocketGetNative(_socket), 
                   SOL_SOCKET, SO_REUSEADDR,
                   (void *)&yes, sizeof(yes));
        uint8_t packetSize = 128;
        setsockopt(CFSocketGetNative(_socket),
                   SOL_SOCKET, SO_SNDBUF,
                   (void *)&packetSize, sizeof(packetSize));
        setsockopt(CFSocketGetNative(_socket),
                   SOL_SOCKET, SO_RCVBUF,
                   (void *)&packetSize, sizeof(packetSize));
        struct sockaddr_in addr4;
        memset(&addr4, 0, sizeof(addr4));
        addr4.sin_len = sizeof(addr4);
        addr4.sin_family = AF_INET;
        addr4.sin_port = htons(CHAT_SERVER_PORT); 
        addr4.sin_addr.s_addr = htonl(INADDR_ANY);
        NSData *address4 = [NSData dataWithBytes:&addr4 length:sizeof(addr4)];
        if (kCFSocketSuccess != CFSocketSetAddress(_socket, (CFDataRef)address4)) {
            if (error) *error = [[NSError alloc] 
                                 initWithDomain:ServerErrorDomain
                                 code:kServerCouldNotBindToIPv4Address
                                 userInfo:nil];
            if (_socket) CFRelease(_socket);
            _socket = NULL;
            successful = NO;
        } else {
            // now that the binding was successful, we get the port number 
            NSData *addr = [(NSData *)CFSocketCopyAddress(_socket) autorelease];
            memcpy(&addr4, [addr bytes], [addr length]);
            self.port = ntohs(addr4.sin_port);
            // 将socket 输入源加入到当前的runloop
            CFRunLoopRef cfrl = CFRunLoopGetCurrent();
            CFRunLoopSourceRef source4 = CFSocketCreateRunLoopSource(kCFAllocatorDefault, _socket, 0);
            CFRunLoopAddSource(cfrl, source4, kCFRunLoopDefaultMode);
            CFRelease(source4);             
            //标准输入，当在命令行中输入时，回调函数便会被调用
            CFFileDescriptorContext context = {0,self,NULL,NULL,NULL};
            CFFileDescriptorRef stdinFDRef = CFFileDescriptorCreate(kCFAllocatorDefault, STDIN_FILENO, true, FileDescriptorCallBack, &context);
            CFFileDescriptorEnableCallBacks(stdinFDRef,kCFFileDescriptorReadCallBack);
            CFRunLoopSourceRef stdinSource = CFFileDescriptorCreateRunLoopSource(kCFAllocatorDefault, stdinFDRef, 0);
            CFRunLoopAddSource(cfrl, stdinSource, kCFRunLoopDefaultMode);
            CFRelease(stdinSource);
            CFRelease(stdinFDRef); 
            CFRunLoopRun();
        }
    }
    return successful;
}

static void SocketConnectionAcceptedCallBack(CFSocketRef socket, 
                                             CFSocketCallBackType type, 
                                             CFDataRef address, 
                                             const void *data, void *info) {
    ChatServer *theChatServer = (ChatServer *)info;
    if (kCFSocketAcceptCallBack == type) { 
        // 摘自kCFSocketAcceptCallBack的文档，New connections will be automatically accepted and the callback is called with the data argument being a pointer to a CFSocketNativeHandle of the child socket. This callback is usable only with listening sockets.
        CFSocketNativeHandle nativeSocketHandle = *(CFSocketNativeHandle *)data;
        // create the read and write streams for the connection to the other process
        CFReadStreamRef readStream = NULL;
        CFWriteStreamRef writeStream = NULL;
        CFStreamCreatePairWithSocket(kCFAllocatorDefault, nativeSocketHandle,
                                     &readStream, &writeStream);
        if(NULL != readStream && NULL != writeStream) {
            CFReadStreamSetProperty(readStream, 
                                    kCFStreamPropertyShouldCloseNativeSocket,
                                    kCFBooleanTrue);
            CFWriteStreamSetProperty(writeStream, 
                                     kCFStreamPropertyShouldCloseNativeSocket,
                                     kCFBooleanTrue);
            NSInputStream *inputStream = (NSInputStream *)readStream;//toll-free bridging
            NSOutputStream *outputStream = (NSOutputStream *)writeStream;//toll-free bridging
            inputStream.delegate = theChatServer;
            [inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
            [inputStream open];
            outputStream.delegate = theChatServer;
            [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
            [outputStream open];
            Client *aClient = [[Client alloc] init];
            aClient.inputStream = inputStream;
            aClient.outputStream = outputStream;
            aClient.sock_fd = nativeSocketHandle;
            [theChatServer.clients setValue:aClient  
                                     forKey:[NSString stringWithFormat:@"%d",inputStream]];
            NSLog(@"有新客户端(sock_fd=%d)加入",nativeSocketHandle);
        } else {
            close(nativeSocketHandle);
        }
        if (readStream) CFRelease(readStream);
        if (writeStream) CFRelease(writeStream);
    }
}

 
- (void) stream:(NSStream*)stream handleEvent:(NSStreamEvent)eventCode {
    switch (eventCode) {
        case NSStreamEventOpenCompleted: {
            break;
        }
        case NSStreamEventHasBytesAvailable: {
            Client *client = [self.clients objectForKey:[NSString stringWithFormat:@"%d",stream]];
            NSMutableData *data = [NSMutableData data];
            uint8_t *buf = calloc(128, sizeof(uint8_t));
            NSUInteger len = 0;
            while([(NSInputStream*)stream hasBytesAvailable]) {
                len = [(NSInputStream*)stream read:buf maxLength:128];
                if(len > 0) {
                    [data appendBytes:buf length:len];
                }
            }
            free(buf);
            if ([data length] == 0) {
                //客户端退出
                NSLog(@"客户端(sock_fd=%d)退出",client.sock_fd);
                [self.clients removeObjectForKey:[NSString stringWithFormat:@"%d",stream]];
                close(client.sock_fd);
            }else{
                NSLog(@"收到客户端(sock_fd=%d)消息:%@",client.sock_fd,[[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]);
            }
            break;
        }
        case NSStreamEventHasSpaceAvailable: {
            break;
        }
        case NSStreamEventEndEncountered: {
            break;
        }
        case NSStreamEventErrorOccurred: {
            break;
        }
        default:
            break;
    }
}

static void FileDescriptorCallBack(CFFileDescriptorRef f,
                                   CFOptionFlags callBackTypes,
                                   void *info){
    int fd = CFFileDescriptorGetNativeDescriptor(f);
    ChatServer *theChatServer = (ChatServer *)info;
    if (fd == STDIN_FILENO) {
        NSData *inputData = [[NSFileHandle fileHandleWithStandardInput] availableData];
        NSString *inputString = [[[NSString alloc] initWithData:inputData encoding:NSUTF8StringEncoding] autorelease];
        NSLog(@"准备发送消息:%@",inputString);
        for (Client *client in [theChatServer.clients allValues]) {
            [client.outputStream write:[inputData bytes] maxLength:[inputData length]];
        }
        //处理完数据之后必须重新Enable 回调函数
        CFFileDescriptorEnableCallBacks(f,kCFFileDescriptorReadCallBack);
    }
}

/* Returns the default singleton instance.*/
+ (NSFileManager *)defaultManager;

- (BOOL)createDirectoryAtPath:(NSString *)path withIntermediateDirectories:(BOOL)createIntermediates attributes:(NSDictionary *)attributes error:(NSError **)error;

- (NSArray *)contentsOfDirectoryAtPath:(NSString *)path error:(NSError **)error;

- (BOOL)copyItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **)error;
- (BOOL)moveItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **)error;
- (BOOL)linkItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **)error;
- (BOOL)removeItemAtPath:(NSString *)path error:(NSError **)error;

@interface Address : NSObject<NSCoding>{
    NSString *country;
    NSString *city;
}
@property(nonatomic,copy) NSString *country;
@property(nonatomic,copy) NSString *city;
@end
//////////////////////////////////////////////////////
#import "Address.h"

@implementation Address
@synthesize country;
@synthesize city;

- (void)encodeWithCoder:(NSCoder *)aCoder{
    [aCoder encodeObject:country forKey:@"country"];
    [aCoder encodeObject:city forKey:@"city"];
}

- (id)initWithCoder:(NSCoder *)aDecoder{
    if (self = [super init]) {
        [self setCountry:[aDecoder decodeObjectForKey:@"country"]];
        [self setCity:[aDecoder decodeObjectForKey:@"city"]];
    }
    return self;
}

@end

#import <Foundation/Foundation.h>
#import "Address.h"
@interface User : NSObject<NSCoding>{
    NSString *_name;
    NSString *_password;

    Address *_address;
}
@property(nonatomic,copy) NSString *name;
@property(nonatomic,copy) NSString *password;
@property(nonatomic,retain) Address *address;

@end
/////////////////////////////////////////////////////////
#import "User.h"

@implementation User
@synthesize name = _name;
@synthesize password = _password;
@synthesize address = _address;

- (void)encodeWithCoder:(NSCoder *)aCoder{
    [aCoder encodeObject:_name forKey:@"name"];
    [aCoder encodeObject:_password forKey:@"password"];
    [aCoder encodeObject:_address forKey:@"address"];
}
- (id)initWithCoder:(NSCoder *)aDecoder{
    if (self = [super init]) {
        [self setName:[aDecoder decodeObjectForKey:@"name"]];
        [self setPassword:[aDecoder decodeObjectForKey:@"password"]];
        [self setAddress:[aDecoder decodeObjectForKey:@"address"]];
    }
    return self;
}
@end

Address *myAddress = [[[Address alloc] init] autorelease];
myAddress.country = @"中国";
myAddress.city = @"杭州";
 
User *user = [[[User alloc] init] autorelease];
user.name = @"卢克";
user.password = @"lukejin";
user.address = myAddress;

[NSKeyedArchiver archiveRootObject:user toFile:@"/Users/Luke/Desktop/user"];

id object = [NSKeyedUnarchiver unarchiveObjectWithFile:@"/Users/Luke/Desktop/user"];
NSLog(@"Object Class : %@",[object class]);

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/ PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>$archiver</key>
    <string>NSKeyedArchiver</string>
    <key>$objects</key>
    <array>
        <string>$null</string>
        <dict>
            <key>$class</key>
            <dict>
                <key>CF$UID</key>
                <integer>8</integer>
            </dict>
            <key>address</key>
            <dict>
                <key>CF$UID</key>
                <integer>4</integer>
            </dict>
            <key>name</key>
            <dict>
                <key>CF$UID</key>
                <integer>2</integer>
            </dict>
            <key>password</key>
            <dict>
                <key>CF$UID</key>
                <integer>3</integer>
            </dict>
        </dict>
        <string>卢克</string>
        <string>lukejin</string>
        <dict>
            <key>$class</key>
            <dict>
                <key>CF$UID</key>
                <integer>7</integer>
            </dict>
            <key>city</key>
            <dict>
                <key>CF$UID</key>
                <integer>6</integer>
            </dict>
            <key>country</key>
            <dict>
                <key>CF$UID</key>
                <integer>5</integer>
            </dict>
        </dict>
        <string>中国</string>
        <string>杭州</string>
        <dict>
            <key>$classes</key>
            <array>
                <string>Address</string>
                <string>NSObject</string>
            </array>
            <key>$classname</key>
            <string>Address</string>
        </dict>
        <dict>
            <key>$classes</key>
            <array>
                <string>User</string>
                <string>NSObject</string>
            </array>
            <key>$classname</key>
            <string>User</string>
        </dict>
    </array>
    <key>$top</key>
    <dict>
        <key>root</key>
        <dict>
            <key>CF$UID</key>
            <integer>1</integer>
        </dict>
    </dict>
    <key>$version</key>
    <integer>100000</integer>
</dict>
</plist>

 
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile;

 
NSMutableDictionary *dataDictionary = [[[NSMutableDictionary alloc] init] autorelease];
 [dataDictionary setValue:[NSNumber numberWithInt:222] forKey:@"intNumber"];
 [dataDictionary setValue:[NSArray arrayWithObjects:@"1",@"2", nil] forKey:@"testArray"];
 [dataDictionary writeToFile:@"/Users/Luke/Desktop/test.plist" atomically:YES];

  
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>intNumber</key>
    <integer>222</integer>
    <key>testArray</key>
    <array>
        <string>1</string>
        <string>2</string>
    </array>
</dict>
</plist>

    
NSDictionary *dictionaryFromFile = [NSDictionary dictionaryWithContentsOfFile:@"/Users/Luke/Desktop/test.plist"];

    
NSMutableDictionary *dataDictionary = [[[NSMutableDictionary alloc] init] autorelease];
[dataDictionary setValue:[NSNumber numberWithInt:222] forKey:@"intNumber"];
[dataDictionary setValue:[NSArray arrayWithObjects:@"1",@"2", nil] forKey:@"testArray"];

NSString *error;
NSData *xmlData = [NSPropertyListSerialization dataFromPropertyList:dataDictionary
                                                           format:NSPropertyListXMLFormat_v1_0
                                                 errorDescription:&error];
if(xmlData) {
    NSLog(@"No error creating XML data.");
    [xmlData writeToFile:@"/Users/Luke/Desktop/test2.plist" atomically:YES];
}
else {
    if (error) {
        NSLog(@"error:%@", error);
        [error release];
    }
}

    
    NSDictionary *dictionaryFromFile = (NSDictionary *)[NSPropertyListSerialization 
                                                       propertyListWithData:[NSData dataWithContentsOfFile:@"/Users/Luke/Desktop/test2.plist"] 
                                                        options:0
                                                        format:NULL
                                                        error:&error];

man defaults

+ (NSUserDefaults *)standardUserDefaults

    
$ sqlite3 test.db
SQLite version 3.7.5
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite>create table if not exists names(id integer primary key asc, name text); 
sqlite> insert into names(name) values('Luke');
sqlite> select * from names;
1|Luke
sqlite> 

    
sqlite3 *database;//sqlite3的类型其实只是一个结构体struct
NSArray *documentsPaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory 
                                                         , NSUserDomainMask 
                                                         , YES); 
NSString *databaseFilePath=[[documentsPaths objectAtIndex:0] stringByAppendingPathComponent:@"luke.db"];

//打开数据库
if (sqlite3_open([databaseFilePath UTF8String], &database)==SQLITE_OK) { 
    NSLog(@"open sqlite db ok."); 
    char *errorMsg; 
    const char *createSql="create table if not exists names (id integer primary key asc,name text)";
    //创建表
    if (sqlite3_exec(database, createSql, NULL, NULL, &errorMsg)==SQLITE_OK) { 
        NSLog(@"create ok."); 
    }else {
        NSLog(@"error: %s",errorMsg); 
        sqlite3_free(errorMsg);
    }
    
    
    //插入数据
    const char *insertSql="insert into names (name) values(\"Luke\")"; 
    if (sqlite3_exec(database, insertSql, NULL, NULL, &errorMsg) == SQLITE_OK) { 
        NSLog(@"insert ok."); 
    }else {
        NSLog(@"error: %s",errorMsg); 
        sqlite3_free(errorMsg); 
    }
    
    
    const char *selectSql="select id,name from names"; 
    sqlite3_stmt *statement; 
    if (sqlite3_prepare_v2(database, selectSql, -1, &statement, nil) == SQLITE_OK) { 
        NSLog(@"select ok.");
    }
    
    while (sqlite3_step(statement)==SQLITE_ROW) { 
        int _id=sqlite3_column_int(statement, 0); 
        char *name=(char *)sqlite3_column_text(statement, 1); 
        NSString *nameString = [NSString stringWithCString:name encoding:NSUTF8StringEncoding];
        NSLog(@"row>>id %i, name %@",_id,nameString); 
    }
    
    sqlite3_finalize(statement);
    
}

sqlite3_close(database);

int multiplier = 2;   
int (^myBlock)(int) = ^(int num){   
    return num * multiplier;   
};   
printf("%d",myBlock(4));   

void (^blockReturningVoidWithVoidArgument)(void);   
int (^blockReturningIntWithIntAndCharArguments)(int, char);   
void (^arrayOfTenBlocksReturningVoidWithIntArgument[10])(int);

typedef float (^MyBlockType)(float, float);   
MyBlockType myFirstBlock = // ... ;   
MyBlockType mySecondBlock = // ... ;

blockReturningVoidWithVoidArgument = ^{   
      printf("%s","Block Returing Void With Void Argument.");   
}

void (^blockReturningVoidWithVoidArgument)(void) = ^{   
      printf("%s","Block Returing Void With Void Argument.");   
}

void callVoidVoid(void (^closure)(void)) {   
   closure();   
}   
int main(int argc, char *argv[]) {   
    __block int i = 10;       
    callVoidVoid(^{ ++i; });   
   if (i != 11) {   
       printf("*** %s didn't update i\n", argv[0]);   
       return 1;   
   }   
   printf("%s: success\n", argv[0]);   
   return 0;   
}

^{ ++i; }();

__block int blockValue = 0;
int autoValue = 0;

void(^printValue)(void) = ^{
    printf("blockValue = %d\n",blockValue);
    printf("autoValue = %d\n",autoValue);

};
blockValue ++;
autoValue ++;
printValue();

blockValue = 1
autoValue = 0

Semantic Issue: Variable is not assignable (missing __block type specifier)

NSObject *testObject = [[NSObject alloc] init];

NSLog(@"%lu",[testObject retainCount]); //1
NSLog(@"%lu",[self retainCount]); //1

void(^testBlock)(void) = ^{
       NSLog(@"The Test String : %@", testObject);
   NSLog(@"The Window Object : %@", _window);
};

NSLog(@"%lu",[testObject retainCount]); //1
NSLog(@"%lu",[self retainCount]); //1
  
void(^testBlock2)(void) = Block_copy(testBlock); //testBlock会被拷贝到heap中,所以用完了要自己调用Block_release进行释放
NSLog(@"%lu",[testObject retainCount]); //2
NSLog(@"%lu",[self retainCount]); //2

testBlock2();

Block_release(testBlock2);

NSLog(@"%lu",[testObject retainCount]); //1
NSLog(@"%lu",[self retainCount]); //1

[testObject release];

[UIView animateWithDuration:2 
               animations:^{
                    self.view.backgroundColor = [UIColor redColor];
                }  
                completion:^(BOOL finished){
                    if (finished){
                        self.view.backgroundColor = [UIColor blueColor];
                    } 
                }];

NSArray *cards = [NSArray arrayWithObjects:@"Jack", @"Queen", @"King", @"Ace", nil];
[cards enumerateObjectsUsingBlock:^(id object, NSUInteger index, BOOL *stop) {
     NSLog(@"%@ card at index %d", object, index);
 }];

    
[[NSNotificationCenter defaultCenter] 
 addObserverForName:@"TestNotification" 
 object:nil 
 queue:aNSOperationQueue 
 usingBlock:^(NSNotification *notification){
     NSLog(@"Notification: %@",notification);
 }];

    
dispatch_queue_t imageDownloadQueue = dispatch_queue_create("Image Download Queue", NULL);
dispatch_async(imageDownloadQueue, ^{
    NSURL *imageURL = [NSURL URLWithString:@"http://xxx.xx.com/a.png"];
    NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
    UIImage *image = [UIImage imageWithData:imageData];
    dispatch_async(dispatch_get_main_queue(), ^{
        [imageView setImage:image];
    });
});

for path in "$@"
do
mv "$path" "$path".tmp
/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/pngcrush -revert-iphone-optimizations "$path".tmp "$path"
rm "$path".tmp
done

- (id)copyWithZone:(NSZone *)zone
{
    id cellCopy = [super copyWithZone:zone];
    /* Assume that other initialization takes place here. */
 
    cellCopy->titleCell = nil;
    [cellCopy setTitleCell:[self titleCell]];
 
    return cellCopy;
}