iOS 開發多線程 —— NSOperation，iosnsoperation

iOS 開發多線程 —— NSOperation，iosnsoperation
本文是根據文頂頂老師的部落格學習而來，轉載地址：http://www.cnblogs.com/wendingding/p/3809042.html一、NSOperation簡介

1.簡單說明

NSOperation的作⽤：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）系統會⾃動將NSOperationQueue中的NSOperation取出來

（4）將取出的NSOperation封裝的操作放到⼀條新線程中執⾏

 2.NSOperation的子類

NSOperation是個抽象類別,並不具備封裝操作的能力,必須使⽤它的子類

使用NSOperation⼦類的方式有3種：

（1）NSInvocationOperation

（2）NSBlockOperation

（3）自訂子類繼承NSOperation,實現內部相應的⽅法

 

NSInvocationOperation:

範例程式碼：

- (void)viewDidLoad {    [super viewDidLoad];        NSInvocationOperation *operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(thread1) object:nil];    [operation start];    NSInvocationOperation *operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(thread2) object:nil];    [operation2 start];    }-(void)thread1{    NSLog(@"currentThread = %@",[NSThread currentThread]);}-(void)thread2{   NSLog(@"currentThread2 = %@",[NSThread currentThread]);}

 currentThread = <NSThread: 0x17406d780>{number = 1, name = main}currentThread2 = <NSThread: 0x17406d780>{number = 1, name = main}

可以看見，並沒有開啟新的線程.

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:

 NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"operation = %@",[NSThread currentThread]);    }];    [operation3 start];看列印結果：operation = <NSThread: 0x1700728c0>{number = 1, name = main}

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

例如：

NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"operation = %@",[NSThread currentThread]);    }];    [operation3 addExecutionBlock:^{        NSLog(@"operation2 = %@",[NSThread currentThread]);    }];    [operation3 start];然後看列印結果：operation = <NSThread: 0x1700706c0>{number = 1, name = main}operation2 = <NSThread: 0x170075a40>{number = 4, name = (null)}

 

NSOperationQueue:

NSOperationQueue的作⽤：NSOperation可以調⽤start⽅法來執⾏任務,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

 

樣本：

- (void)viewDidLoad {    [super viewDidLoad];        NSInvocationOperation *operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(thread1) object:nil];    NSInvocationOperation *operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(thread2) object:nil];               NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{        NSLog(@"currentThread3 = %@",[NSThread currentThread]);    }];        [operation3 addExecutionBlock:^{        NSLog(@"currentThread3_1 = %@",[NSThread currentThread]);    }];        NSOperationQueue *queue = [[NSOperationQueue alloc]init];    //把操作添加到隊列中    //第一種方式    [queue addOperation:operation1];    [queue addOperation:operation2];    [queue addOperation:operation3];    //第二種方式    [queue addOperationWithBlock:^{        NSLog(@"currentThread4 = %@",[NSThread currentThread]);    }];    }-(void)thread1{    NSLog(@"currentThread1 = %@",[NSThread currentThread]);}-(void)thread2{   NSLog(@"currentThread2 = %@",[NSThread currentThread]);}

查看結果：

currentThread1 = <NSThread: 0x17006f440>{number = 4, name = (null)}currentThread2 = <NSThread: 0x17007d9c0>{number = 5, name = (null)}currentThread3_1 = <NSThread: 0x17007d9c0>{number = 5, name = (null)}currentThread3 = <NSThread: 0x17006f440>{number = 4, name = (null)}currentThread4 = <NSThread: 0x17007d9c0>{number = 5, name = (null)}