ios多線程 -- NSOperation 簡介

標籤：

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）然後將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是個抽象類別,並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）自訂子類繼承NSOperation,實現內部相應的?法

NSInvocationOperation 開啟任務方法

//用 NSInvocationOperation 建立線程    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);}

將建立的任務添加到隊列中,非同步執行

- (void)invocationOperation{    //用 NSInvocationOperation 建立線程    NSInvocationOperation *invocation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download:) object:@"NSInvocationOperation"];      //建立全域隊列(實現非同步並發執行)    NSOperationQueue *queue = [[NSOperationQueue alloc] init];    //從對列中取出任務執行(非同步)    [queue addOperation:invocation];}- (void)download:(NSString *)url{    NSLog(@"%@ --- %@", [NSThread currentThread], url);}

注意:操作對象預設在主線程中執行，只有添加到隊列中才會開啟新的線程。即預設情況下，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,才會非同步執行操作

NSBlockOperation 開啟任務的方法

NSBlockOperation 新增工作- (void)blockOperation2{    //建立任務    NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"下載圖片1 --- %@", [NSThread currentThread]);    }];    [operation1 start];}

注意:只要NSBlockOperation封裝的運算元 > 1,就會非同步執行操作

- (void)blockOperation2{    //注意:只要NSBlockOperation封裝的運算元 > 1,就會非同步執行操作    //建立任務    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,但預設是同步執行的
如果將NSOperation添加到NSOperationQueue(操作隊列)中,系統會自動非同步執行NSOperation中的操作
添加操作到NSOperationQueue中，自動執行操作，自動開啟線程
擷取 NSOperationQueue 隊列:

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

新增工作有兩個方法:

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

執行個體代碼

- (void)blockOperation{    //建立全域隊列(實現非同步並發執行)    NSOperationQueue *queue = [[NSOperationQueue alloc] init];//並發隊列    //NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];//主隊列    //建立任務    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{    //建立全域隊列(實現非同步並發執行)    NSOperationQueue *queue = [[NSOperationQueue alloc] init];    //直接向隊列中新增工作    [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]);    }];}

ios多線程 -- NSOperation 簡介