iOS开发之Block常见用法

Block的常见几个用途

1.简化枚举

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NSArray *array = ...    [array enumerateObjectsUsingBlock:^ (id obj, NSUInteger idx, BOOL *stop) {        NSLog(@"Object at index %lu is %@", idx, obj);    }];

2.简化并发任务

• 使用于OperationQueue

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NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{    ...}];// schedule task on main queue:NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];[mainQueue addOperation:operation];// schedule task on background queue:NSOperationQueue *queue = [[NSOperationQueue alloc] init];[queue addOperation:operation];

• 使用于GCD

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dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);dispatch_async(queue, ^{    NSLog(@"Block for asynchronous execution");});