6.13 Running Tasks Asynchronously with Operations

并发执行operation

使用opération queue  或 子类化NSOperation 并在main方法里面detach一个线程来执行。

- (void) firstOperationEntry:(id)paramObject{

    NSLog(@"%s", __FUNCTION__);

    NSLog(@"Parameter Object = %@", paramObject);

    NSLog(@"Main Thread = %@", [NSThread mainThread]);

    NSLog(@"Current Thread = %@", [NSThread currentThread]);

}

- (void) secondOperationEntry:(id)paramObject{

    NSLog(@"%s", __FUNCTION__);

    NSLog(@"Parameter Object = %@", paramObject);

    NSLog(@"Main Thread = %@", [NSThread mainThread]);

    NSLog(@"Current Thread = %@", [NSThread currentThread]);

}

NSOperationQueue *operationQueue;

NSInvocationOperation *firstOperation;

NSInvocationOperation *secondOperation;

-(void)test6_13

{

    

    NSNumber *firstNumber = [NSNumber numberWithInteger:111];

    NSNumber *secondNumber = [NSNumber numberWithInteger:222];

    firstOperation =[[NSInvocationOperation alloc] initWithTarget:self selector:@selector(firstOperationEntry:) object:firstNumber];

    secondOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(secondOperationEntry:) object:secondNumber];

    operationQueue = [[NSOperationQueue alloc] init];

    

    /* Add the operations to the queue */

    [operationQueue addOperation:firstOperation];

    [operationQueue addOperation:secondOperation];

    NSLog(@"Main thread is here");

}

输出

2014-03-11 17:08:00.381 cookbook[547:360b] -[AppDelegate secondOperationEntry:]

2014-03-11 17:08:00.381 cookbook[547:a0b] Main thread is here

2014-03-11 17:08:00.381 cookbook[547:1403] -[AppDelegate firstOperationEntry:]

2014-03-11 17:08:00.382 cookbook[547:360b] Parameter Object = 222

2014-03-11 17:08:00.383 cookbook[547:1403] Parameter Object = 111

2014-03-11 17:08:00.384 cookbook[547:360b] Main Thread = <NSThread: 0x896ec60>{name = (null), num = 1}

2014-03-11 17:08:00.385 cookbook[547:1403] Main Thread = <NSThread: 0x896ec60>{name = (null), num = 1}

2014-03-11 17:08:00.385 cookbook[547:360b] Current Thread = <NSThread: 0x8c76570>{name = (null), num = 2}

2014-03-11 17:08:00.385 cookbook[547:1403] Current Thread = <NSThread: 0xdb5d2f0>{name = (null), num = 3}

可以看出主线程没有被锁

如何来写自己的NSOperation呢，有几点要注意

1，因为加到opération queue以后，opération 将异步运行，所以必须重写isConcurrent方法，并返回yes

2，注意此operation 是否被取消，在main之前以及执行任务过程中要注意此操作是否已经取消了。

3，重写main方法，并在里面使用自动释放池

4，重写is finished 和isExecuting 方法。

.h文件

@interface SimpleOperation : NSOperation

/* Designated Initializer */

- (id) initWithObject:(NSObject *)paramObject;

@end

.m文件

@implementation SimpleOperation

NSObject *givenObject;

BOOL finished;

BOOL executing;

- (id) init {

    NSNumber *dummyObject = [NSNumber numberWithInteger:123];

    return([self initWithObject:dummyObject]);

}

- (id) initWithObject:(NSObject *)paramObject{

    self = [super init];

    if (self != nil){

        /* Keep these values for the main method */

        givenObject = paramObject;

    }

    return(self);

}

- (void) start {

    /* If we are cancelled before starting, then

     we have to return immediately and generate the required KVO notifications */

    if ([self isCancelled]){

        /* If this operation *is* cancelled */

        /* KVO compliance */

        [self willChangeValueForKey:@"isFinished"];

        finished = YES;

        [self didChangeValueForKey:@"isFinished"];

        return;

    } else {

        /* If this operation is *not* cancelled */

        /* KVO compliance */

        [self willChangeValueForKey:@"isExecuting"];

        executing = YES;

        /* Call the main method from inside the start method */

        [self didChangeValueForKey:@"isExecuting"];

        [self main];

    }

}

- (void) main {

    @try {

        @autoreleasepool {

        /* Keep a local variable here that must get set to YES whenever we are done with the task */

        BOOL taskIsFinished = NO;

        /* Create a while loop here that only exists

         if the taskIsFinished variable is set to YES or the operation has been cancelled */

      

        while (taskIsFinished == NO && [self isCancelled] == NO){

            /* Perform the task here */

            NSLog(@"%s", __FUNCTION__);

            NSLog(@"Parameter Object = %@", givenObject);

            NSLog(@"Main Thread = %@", [NSThread mainThread]);

            NSLog(@"Current Thread = %@", [NSThread currentThread]);

            /* Very important. This way we can get out of the

             loop and we are still complying with the cancellation rules of operations */

            taskIsFinished = YES;

        }

        /* KVO compliance. Generate the required KVO notifications */

        [self willChangeValueForKey:@"isFinished"];

        [self willChangeValueForKey:@"isExecuting"];

        finished = YES;

        executing = NO;

        [self didChangeValueForKey:@"isFinished"];

        [self didChangeValueForKey:@"isExecuting"];

        }

    }

    @catch (NSException * e) {

        NSLog(@"Exception %@", e);

    }

}

- (BOOL) isConcurrent{

    return YES;

}

- (BOOL) isFinished{

    /* Simply return the value */

    return finished;

}

- (BOOL) isExecuting{

    /* Simply return the value */

    return executing;

}

@end

调用测试：

-(void)test6_13_1

{

    SimpleOperation *firstOperation;

    SimpleOperation *secondOperation;

    NSNumber *firstNumber = [NSNumber numberWithInteger:111];

    NSNumber *secondNumber = [NSNumber numberWithInteger:222];

    firstOperation =[[SimpleOperation alloc] initWithObject:firstNumber];

    secondOperation = [[SimpleOperation alloc] initWithObject: secondNumber];

    operationQueue = [[NSOperationQueue alloc] init];

    

    /* Add the operations to the queue */

    [operationQueue addOperation:firstOperation];

    [operationQueue addOperation:secondOperation];

    NSLog(@"Main thread is here");

}

输出：

2014-03-12 09:21:00.723 cookbook[385:a0b] Main thread is here

2014-03-12 09:21:00.723 cookbook[385:1403] -[SimpleOperation main]

2014-03-12 09:21:00.723 cookbook[385:360b] -[SimpleOperation main]

2014-03-12 09:21:00.724 cookbook[385:1403] Parameter Object = 222

2014-03-12 09:21:00.724 cookbook[385:360b] Parameter Object = 222

2014-03-12 09:21:00.725 cookbook[385:360b] Main Thread = <NSThread: 0x8978e80>{name = (null), num = 1}

2014-03-12 09:21:00.725 cookbook[385:1403] Main Thread = <NSThread: 0x8978e80>{name = (null), num = 1}

2014-03-12 09:21:00.726 cookbook[385:1403] Current Thread = <NSThread: 0x8e67b40>{name = (null), num = 3}

2014-03-12 09:21:00.726 cookbook[385:360b] Current Thread = <NSThread: 0x8983b80>{name = (null), num = 2}