多线程编程(三种方式)

一、NSThread

DownloadFile是一个继承NSObject的类，当中的runDownload方法是需要放到线程中执行；ThreadDownload则是一个继承NSThread的子线程类，配合隐式创建线程的方式，执行threadD对象中的run:函数并传入字符串@"download3"

// download
DownloadFile *download = [[DownloadFile alloc] init];

// 动态创建线程
NSThread *downloadThread = [[NSThread alloc] initWithTarget:download selector:@selector(runDownload:) object:@"download1"];
[downloadThread start];

// 暂停当前线程2秒
[NSThread sleepForTimeInterval:2];

// 静态方法创建线程
[NSThread detachNewThreadSelector:@selector(runDownload:) toTarget:download withObject:@"download2"];

// 隐式创建线程
ThreadDownload *threadD = [[ThreadDownload alloc] init];
[threadD performSelectorInBackground:@selector(run:) withObject:@"download3"];

[self performSelectorInBackground:@selector(mainRun:) withObject:@"download4"];

二、配合使用NSOperation和NSOperationQueue实现多线程编程

NSOperationQueue *queue = [[NSOperationQueue alloc] init];

// 使用NSOperation的子类NSBlokOperation
NSBlockOperation *blockOperation = [NSBlockOperation blockOperationWithBlock:^{
     NSLog(@"blockOperation--------%@", [NSThread currentThread]);
}];
blockOperation.completionBlock = ^() {
     NSLog(@"blockOperation 执行完毕!");
};
//    [blockOperation start];
//    [[NSOperationQueue mainQueue] addObject:blockOperation];

// 使用NSOperation的子类NSInvocationOperation
NSInvocationOperation *invocationOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(mainRun:) object:@"invocationOperation"];
invocationOperation.completionBlock = ^() {
    NSLog(@"invocationOperation 执行完毕!");
};

// 设置依赖关系，前者依赖于后者，当两个operation都放入queue中时，后者先运行于前者
[invocationOperation addDependency:blockOperation];

// 放入操作队列(NSOperationQueue)中，实现异步多线程操作
[queue addOperation:blockOperation];

// 暂停queue 2秒后 恢复queue
[queue setSuspended:YES];
[NSThread sleepForTimeInterval:2.0];
[queue setSuspended:NO];

[queue addOperation:invocationOperation];

三、GCD线程管理(推荐)

// GCD并行操作 任务并发执行
// 并行可不需显示创建，每次都直接调用dispatch_get_global_queue获得queue就行了
dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(concurrentQueue, ^{
        NSLog(@"GCD并行异步任务1------%@", [NSThread currentThread]);
});
dispatch_async(concurrentQueue, ^{
        NSLog(@"GCD并行异步任务2------%@", [NSThread currentThread]);
});

// GCD串行操作 会按照添加的任务顺序，先进先出，前一个任务完成才执行下一个
// 串行需要显示创建，可以创建多个串行队列，串行队列也可以并行执行，但决不能随意的大量创建串行队列
dispatch_queue_t serialQueue = dispatch_queue_create("our_serial_queue", NULL);
dispatch_async(serialQueue, ^{
        NSLog(@"GCD串行异步任务1------%@", [NSThread currentThread]);
});
dispatch_async(serialQueue, ^{
        NSLog(@"GCD串行异步任务2------%@", [NSThread currentThread]);
});

// Dispatch Group的使用 -> 并行执行多个任务，然后等待全部任务完成再回到主线程执行任务
[NSThread sleepForTimeInterval:2.0];

NSLog(@"******************************************GCD**********************************************");

dispatch_async(concurrentQueue, ^{
    dispatch_group_t group = dispatch_group_create();
            
    // 往group添加并行异步任务
    dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            NSLog(@"并发组异步任务1-------%@", [NSThread currentThread]);
　　});
　　dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            NSLog(@"并发组异步任务2-------%@", [NSThread currentThread]);
　　});
            
// 等待组中的任务执行完毕,回到主线程执行block回调
　　dispatch_group_notify(group, dispatch_get_main_queue(), ^{
            NSLog(@"Dispatch Group主线程任务回调!--------%@", [NSThread currentThread]);
   });
});

参考链接:http://www.cnblogs.com/mjios/archive/2013/04/18/3029309.html