NSOperation的作⽤:配合使用NSOperation和NSOperationQueue也能实现多线程编程
NSOperation和NSOperationQueue实现多线程的具体步骤:
1)先将需要履行的操作封装到1个NSOperation对象中
2)然后将NSOperation对象添加到NSOperationQueue中
3)系统会⾃动将NSOperationQueue中的NSOperation取出来
4)将取出的NSOperation封装的操作放到⼀条新线程中执⾏
NSOperation是个抽象类,其实不具有封装操作的能力,必须使⽤它的子类
使用NSOperation⼦类的方式有3种:
1)NSInvocationOperation
2)NSBlockOperation
3)自定义子类继承NSOperation,实现内部相应的⽅法
NSInvocationOperation 开启任务方法
//用 NSInvocationOperation 创建线程
NSInvocationOperation *invocation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download:) object:@"NSInvocationOperation"];
//在当前线程中同步履行
[invocation start];
- (void)download:(NSString *)url{
NSLog(@"%@ --- %@", [NSThread currentThread], url);
}
将创建的任务添加到队列中,异步履行
- (void)invocationOperation{
//用 NSInvocationOperation 创建线程
NSInvocationOperation *invocation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download:) object:@"NSInvocationOperation"];
//创建全局队列(实现异步并发履行)
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
//从对列中取出任务履行(异步)
[queue addOperation:invocation];
}
- (void)download:(NSString *)url{
NSLog(@"%@ --- %@", [NSThread currentThread], url);
}
注意:操作对象默许在主线程中履行,只有添加到队列中才会开启新的线程。即默许情况下,如果操作没有放到队列中queue中,都是同步履行。只有将NSOperation放到1个NSOperationQueue中,才会异步履行操作
NSBlockOperation 开启任务的方法
NSBlockOperation 添加任务
- (void)blockOperation2{
//创建任务
NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"下载图片1 --- %@", [NSThread currentThread]);
}];
[operation1 start];
}
注意:只要NSBlockOperation封装的操作数 > 1,就会异步履行操作
- (void)blockOperation2{
//注意:只要NSBlockOperation封装的操作数 > 1,就会异步履行操作
//创建任务
NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"下载图片1 --- %@", [NSThread currentThread]);
}];
[operation1 addExecutionBlock:^{
NSLog(@"下载图片2 --- %@", [NSThread currentThread]);
}];
[operation1 addExecutionBlock:^{
NSLog(@"下载图片3 --- %@", [NSThread currentThread]);
}];
[operation1 start];
}
NSOperationQueue
NSOperationQueue的作⽤:NSOperation可以调⽤start⽅法来执⾏任务,但默许是同步履行的
如果将NSOperation添加到NSOperationQueue(操作队列)中,系统会自动异步履行NSOperation中的操作
添加操作到NSOperationQueue中,自动履行操作,自动开启线程
获得 NSOperationQueue 队列:
NSOperationQueue *queue = [[NSOperationQueue alloc] init];//并发队列
NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];//主队列
添加任务有两个方法:
- (void)addOperation:(NSOperation *)op;
- (void)addOperationWithBlock:(void (^)(void))block;
实例代码
- (void)blockOperation{
//创建全局队列(实现异步并发履行)
NSOperationQueue *queue = [[NSOperationQueue alloc] init];//并发队列
//NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];//主队列
//创建任务
NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"下载图片1 --- %@", [NSThread currentThread]);
}];
NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"下载图片2 --- %@", [NSThread currentThread]);
}];
NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"下载图片3 --- %@", [NSThread currentThread]);
}];
NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"下载图片4 --- %@", [NSThread currentThread]);
}];
NSBlockOperation *operation5 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"下载图片5 --- %@", [NSThread currentThread]);
}];
//将任务添加到队列中
[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:operation3];
[queue addOperation:operation4];
[queue addOperation:operation5];
}
- (void)queueAddBlock{
//创建全局队列(实现异步并发履行)
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
//直接向队列中添加任务
[queue addOperationWithBlock:^{
NSLog(@"下载图片1 --- %@", [NSThread currentThread]);
}];
[queue addOperationWithBlock:^{
NSLog(@"下载图片2 --- %@", [NSThread currentThread]);
}];
[queue addOperationWithBlock:^{
NSLog(@"下载图片3 --- %@", [NSThread currentThread]);
}];
[queue addOperationWithBlock:^{
NSLog(@"下载图片4 --- %@", [NSThread currentThread]);
}];
[queue addOperationWithBlock:^{
NSLog(@"下载图片5 --- %@", [NSThread currentThread]);
}];
}