Objective-C-NSOperation

摘要: NSBlockOperation，NSInvocztionOperation

NSOpseration是抽象基类，所以要用子类实现它的方法。（内部使用gcd实现）
1.一个NSOperation 就代表一个任务，任务的代码分装在block里或者函数里。
OC提供子类：
NSInvocztionOperation：任务是一个函数，比较长
NSBlockOperation：任务是一个block，比较短

常用方法demo：（有关线程执行方式，队列类型看这里）

1.1NSBlockOperation:

- (void) testBlockOperation2
{
//情况1.
NSBlockOperation *operationA = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"startA:%@", [NSThread currentThread]);
}];
[operationA start];
NSBlockOperation *operationB = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"startB:%@", [NSThread currentThread]);
}];
[operationB start];
NSBlockOperation *operationC = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"startC:%@", [NSThread currentThread]);
}];
[operationC start];

//情况2.
NSBlockOperation *operation = [[ NSBlockOperation alloc] init];
[operation addExecutionBlock:^{
NSLog(@"start1:%@", [NSThread currentThread]);
}];

[operation addExecutionBlock:^{
NSLog(@"start2:%@", [NSThread currentThread]);
}];
[operation addExecutionBlock:^{
NSLog(@"start3:%@", [NSThread currentThread]);
}];
[operation start];
}

可以看到任务配置好以后，直接执行时同步的。而把任务block放到一起的时候是异步的。

- (void) testBlockOperation
{
//情况3.
NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"start1:%@", [NSThread currentThread]);
}];

NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"start2:%@", [NSThread currentThread]);
}];

NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"start3:%@", [NSThread currentThread]);
}];

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[queue addOperations:@[operation3, operation2, operation1] waitUntilFinished:NO];
}

放到全局队列里也是异步的（并发），如果放到主队列（[NSOperationQueue mainQueue]）里，那么是同步的。

1.2NSInvocztionOperation：使用它和NSBlockOperation是一样的。都是NSOperation的子类……

- (void) testOperationInvocation{
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
NSInvocationOperation *operation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(operationFirst:) object:@"start"];
[operation1 start];

NSInvocationOperation *operation2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(operationFirst:) object:@"newQ"];
[queue addOperation:operation2];
}

- (void) operationFirst:(NSString *) who
{
NSLog(@"\n%@, %s, %@", who, __func__, [NSThread currentThread]);
}

2.任务间依赖关系：也是用来实现异步线程间通信的一种约定

- (void) operationDependency
{
NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"thread 1");
}];
[operation1 setCompletionBlock:^{
NSLog(@"finish thread1");
}];
NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"thread 2");
}];
NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"thread 3");
}];

[operation1 addDependency:operation2];
[operation2 addDependency:operation3];

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:operation3];
}

依据依赖顺序执行