iOS异步方法、同步实现

1、GCD实现

-  (int)syncGetCountWithDispatchGroup

{

// _block 修饰才能在block块里面更改值

    __block int count = 0;

    dispatch_group_t  group = dispatch_group_create();

    dispatch_group_enter(group);

// 异步方法

    [self  AsyncGetCount:^(NSInteger value) {

        count = value;

        dispatch_group_leave(group);

    }];

    dispatch_group_wait(group, DISPATCH_TIME_FOREVER);

// 利用线程组阻塞、必须调用异步取值才能走下一步

    return count;

}

-  (void)moreNetLoadWithDispatchGroup

{

    dispatch_group_t  group = dispatch_group_create();

    dispatch_group_enter(group);

// 异步网络方法1

    [self  AsyncLoadrequest1:^(NetModel *value) {

        dispatch_group_leave(group);

    }];

// 异步网络方法2

dispatch_group_enter(group);

[self  AsyncLoadrequest2:^(NetModel *value) {

dispatch_group_leave(group);

    }];

//  必须两个任务走完才能走下一步

    dispatch_group_notify(group, dispatch_get_main_queue(), ^{

                // 最后的操作

    });

}

2、信号量实现

- (int)syncGetCountWithSemaphore

{

    __block int  count = 0;

    dispatch_semaphore_t sema = dispatch_semaphore_create(0);

    [self AsyncGetCount:^(NSInteger value) {

        count = value;

        dispatch_semaphore_signal(sema);

    }];

    dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);

    return result;

}