NSOperation的作?：配合使用NSOperation和NSOperationQueue也能實現多線程編程
NSOperation和NSOperationQueue實現多線程的具體步驟：
1）先將需要執行的操作封裝到一個NSOperation對象中
2）然后將NSOperation對象添加到NSOperationQueue中
3）系統會?動將NSOperationQueue中的NSOperation取出來
4）將取出的NSOperation封裝的操作放到?條新線程中執?

NSOperation是個抽象類,并不具備封裝操作的能力,必須使?它的子類
使用NSOperation?類的方式有3種：
1）NSInvocationOperation
2）NSBlockOperation
3）自定義子類繼承NSOperation,實現內部相應的?法

NSInvocationOperation 開啟任務方法

//用 NSInvocationOperation 創建線程NSInvocationOperation *invocation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download:) object:@"NSInvocationOperation"]; //在當前線程中同步執行 [invocation start];- (void)download:(NSString *)url{NSLog(@"%@ --- %@", [NSThread currentThread], url); }

將創建的任務添加到隊列中,異步執行

- (void)invocationOperation{//用 NSInvocationOperation 創建線程NSInvocationOperation *invocation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download:) object:@"NSInvocationOperation"]; //創建全局隊列(實現異步并發執行)NSOperationQueue *queue = [[NSOperationQueue alloc] init];//從對列中取出任務執行(異步)[queue addOperation:invocation];}- (void)download:(NSString *)url{NSLog(@"%@ --- %@", [NSThread currentThread], url); }

注意:操作對象默認在主線程中執行，只有添加到隊列中才會開啟新的線程。即默認情況下，如果操作沒有放到隊列中queue中，都是同步執行。只有將NSOperation放到一個NSOperationQueue中,才會異步執行操作

NSBlockOperation 開啟任務的方法

NSBlockOperation 添加任務 - (void)blockOperation2{//創建任務NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{NSLog(@"下載圖片1 --- %@", [NSThread currentThread]);}];[operation1 start]; }

注意:只要NSBlockOperation封裝的操作數 > 1,就會異步執行操作

- (void)blockOperation2{//注意:只要NSBlockOperation封裝的操作數 > 1,就會異步執行操作//創建任務NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{NSLog(@"下載圖片1 --- %@", [NSThread currentThread]);}];[operation1 addExecutionBlock:^{NSLog(@"下載圖片2 --- %@", [NSThread currentThread]);}];[operation1 addExecutionBlock:^{NSLog(@"下載圖片3 --- %@", [NSThread currentThread]);}];[operation1 start]; }

NSOperationQueue

NSOperationQueue的作?：NSOperation可以調?start?法來執?任務,但默認是同步執行的
如果將NSOperation添加到NSOperationQueue(操作隊列)中,系統會自動異步執行NSOperation中的操作
添加操作到NSOperationQueue中，自動執行操作，自動開啟線程
獲取 NSOperationQueue 隊列:

NSOperationQueue *queue = [[NSOperationQueue alloc] init];//并發隊列NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];//主隊列

添加任務有兩個方法:

- (void)addOperation:(NSOperation *)op; - (void)addOperationWithBlock:(void (^)(void))block;

實例代碼

- (void)blockOperation{//創建全局隊列(實現異步并發執行)NSOperationQueue *queue = [[NSOperationQueue alloc] init];//并發隊列//NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];//主隊列//創建任務NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{NSLog(@"下載圖片1 --- %@", [NSThread currentThread]);}];NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{NSLog(@"下載圖片2 --- %@", [NSThread currentThread]);}];NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{NSLog(@"下載圖片3 --- %@", [NSThread currentThread]);}];NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{NSLog(@"下載圖片4 --- %@", [NSThread currentThread]);}];NSBlockOperation *operation5 = [NSBlockOperation blockOperationWithBlock:^{NSLog(@"下載圖片5 --- %@", [NSThread currentThread]);}];//將任務添加到隊列中[queue addOperation:operation1];[queue addOperation:operation2];[queue addOperation:operation3];[queue addOperation:operation4];[queue addOperation:operation5]; }

- (void)queueAddBlock{//創建全局隊列(實現異步并發執行)NSOperationQueue *queue = [[NSOperationQueue alloc] init];//直接向隊列中添加任務[queue addOperationWithBlock:^{NSLog(@"下載圖片1 --- %@", [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@"下載圖片2 --- %@", [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@"下載圖片3 --- %@", [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@"下載圖片4 --- %@", [NSThread currentThread]);}];[queue addOperationWithBlock:^{NSLog(@"下載圖片5 --- %@", [NSThread currentThread]);}]; }

轉載于:https://www.cnblogs.com/xiaocai-ios/p/7779775.html

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