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一：队列的类型与队列添加任务1： 主队列[NSOperationQueue mainQueue]添加到”主队列”中的操作，都会放到主线程中执行。2：非主队列[[NSOperationQueue alloc] init]添加到”非主队列”中的操作，都会放到子线程中执行。3：队列添加任务(void)addOperation:(NSOperation *)op;(void)addOperationWithBlock:(void (^)(void))block;二：常见用法1： 设置最大并发数
（1）并发数:同时执行的任务数.比如,同时开3个线程执行3个任务,并发数就是3。 （2）最大并发数：同一时间最多只能执行的任务的个数。 （3）最大并发数的相关方法。 – (NSInteger)maxConcurrentOperationCount; – (void)setMaxConcurrentOperationCount:(NSInteger)cnt; 说明：如果没有设置最大并发数，那么并发的个数是由系统内存和CPU决定的，可能内存多久开多一点，内存少就开少一点。 注意：num的值并不代表线程的个数，仅仅代表线程的ID。 提示：最大并发数不要乱写（5以内），不要开太多，一般以2~3为宜，因为虽然任务是在子线程进行处理的，但是cpu处理这些过多的子线程可能会影响UI，让UI变卡。
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{// 1.创建一个队列（非主队列）NSOperationQueue *queue = [[NSOperationQueue alloc] init];// 2.设置最大并发(最多同时并发执行2个任务)queue.maxConcurrentOperationCount = 2;// 3.添加操作到队列中（自动异步执行任务，并发）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]);}];NSInvocationOperation *operation5 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];[queue addOperation:operation1];[queue addOperation:operation2];[queue addOperation:operation3];[queue addOperation:operation4];[queue addOperation:operation5];[queue addOperationWithBlock:^{NSLog(@”下载图片5—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片6—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片7—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片8—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片9—%@”, [NSThread currentThread]);}];}
效果：我们设置了9个模拟下载的操作，同一时间开启的线程最多为两个，注意，途中有2，3，4 三条线程，但是我们保证了再同一时间只有两条线程，2开始做事，后来不做了，就换线程3，4了。
2： 队列的其他操作取消所有的操作(void)cancelAllOperations;-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{// 1.创建一个队列（非主队列）NSOperationQueue *queue = [[NSOperationQueue alloc] init];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]);}];NSInvocationOperation *operation5 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];[queue addOperation:operation1];[queue addOperation:operation2];[queue addOperation:operation3];[queue addOperation:operation4];[queue addOperation:operation5];[queue addOperationWithBlock:^{NSLog(@”下载图片5—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片6—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片7—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片8—%@”, [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@”下载图片9—%@”, [NSThread currentThread]);}];[queue cancelAllOperations]; }
结果图：
这个的用法其实是在管理内存时候用的
愚公因此敢移山，矢志不渝是前行，握紧拳头勇登攀，
