iOS线程开发小结

在iOS开发线程操作时，一般方法名决定是否开启新线程(async,sync)，队列类型(全局队列，串行队列)决定开启多少条线程

1.快速线程调用

*开启后台线程执行任务

[self performSelectorInBackground:@selector(test) withObject:nil];

*回到主线程执行任务

[self performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:YES];

2.GCD ： 依赖队列执行

1> 队列类型

* 全局队列

* 所有添加到全局队列中的任务都是并发执行（同时执行，可能会开启多个线程）

* dispatch_get_global_queue

* 串行队列

* 所有添加到串行队列中的任务都是按顺序执行（开一条线程）

* dispatch_queue_create("myqueue", 0);

* 主队列

* 所有添加到主队列中的任务都是在主线程中执行的(跟方法名没有关系)

* dispatch_get_main_queue

2> 同步还是异步，取决于方法名(不影响主队列，影响全局队列、串行队列)

* 同步：dispatch_sync,在当前线程执行任务，不会开启新的线程

* 异步：dispatch_async，在其他线程执行任务，会开启新的线程

3.NSOperation\NSOperationQueue

1> 使用步骤

* 创建NSOperation

* 添加NSOperation到NSOperationQueue

2> 优点

* 更加面向对象

* 可以控制最大并发数  maxConcurrentOperationCount

* 添加任务（Operation）之间的依赖 addDependency

*/

#import "XMQViewController.h"

@interface XMQViewController ()

{

NSOperationQueue *_queue;

}

@end

@implementation XMQViewController

- (void)viewDidLoad

{

[super viewDidLoad];

_queue = [[NSOperationQueue alloc] init];

// 控制最大并发数，最多同时执行3条线程

_queue.maxConcurrentOperationCount = 3;

// 回到主线程

//    [self test];

// 线程监听

//    [self gcd_group];

// GCD线程依赖

//    [self gcd_barrier];

// 循环执行

[self gcd_apply];

// 全局队列

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

// 串行队列

//    dispatch_queue_t queue2 = dispatch_queue_create("myqueue", 0);

dispatch_async(queue, ^{ // 耗时操作

NSLog(@"这是一个异步线程---%@", [NSThread currentThread]);

});

}

- (IBAction)click

{

NSOperation *operation = [NSBlockOperation blockOperationWithBlock:^{

NSLog(@"operation---%@", [NSThread currentThread]);

}];

NSOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{

NSLog(@"operation2---%@", [NSThread currentThread]);

}];

// 该方法默认在主线程执行

//    [operation start];

// 加入队列会在异步线程执行

[_queue addOperation:operation];

[_queue addOperation:operation2];

// 设置线程依赖 (operation2依赖于operation，operation执行完以后，才能执行operation2)

[operation addDependency:operation2];

}

// 延时执行某条线程

- (IBAction)click2

{

// 全局队列

//    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

// 串行队列

dispatch_queue_t queue2 = dispatch_queue_create("myqueue", 0);

double delayInSeconds = 5.0;

dispatch_time_t delayInNanoSeconds =dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);

dispatch_after(delayInNanoSeconds, queue2, ^{

NSLog(@"延迟执行");

});

}

// dispatch_group_async(异步方法)可以实现监听一组任务是否完成，完成后得到通知执行其他的操作(比如通知用户下载完成,显示UI等)

- (void)gcd_group

{

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_group_t group = dispatch_group_create();

dispatch_group_async(group, queue, ^{

[NSThread sleepForTimeInterval:1];

NSLog(@"group1");

});

dispatch_group_async(group, queue, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"group2");

});

dispatch_group_async(group, queue, ^{

[NSThread sleepForTimeInterval:3];

NSLog(@"group3");

});

dispatch_group_notify(group, dispatch_get_main_queue(), ^{

NSLog(@"updateUI");

});

}

// dispatch_barrier_async 是在前面的任务执行结束后才执行，而且后面的任务必须等它执行完成之后才会执行

- (void)gcd_barrier

{

dispatch_queue_t queue = dispatch_queue_create("myqueue", DISPATCH_QUEUE_CONCURRENT);

dispatch_async(queue, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"dispatch_async1");

});

dispatch_async(queue, ^{

[NSThread sleepForTimeInterval:4];

NSLog(@"dispatch_async2");

});

dispatch_barrier_async(queue, ^{

NSLog(@"dispatch_barrier_async");

[NSThread sleepForTimeInterval:4];

});

dispatch_async(queue, ^{

[NSThread sleepForTimeInterval:2];

NSLog(@"dispatch_async3");

});

}

// dispatch_apply 执行某个代码片段N次

- (void)gcd_apply

{

dispatch_queue_t queue = dispatch_queue_create("myqueue", DISPATCH_QUEUE_PRIORITY_DEFAULT);

dispatch_apply(10, queue, ^(size_t index) {

NSLog(@"循环执行10次");

});

}

// 回到主线程

- (void)test

{

UIImage *image = nil;

[self performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:YES];

dispatch_async(dispatch_get_main_queue(), ^{

NSLog(@"更新UI界面---%@", [NSThread currentThread]);

});

}

@end