我正在调用我想以同步顺序执行的四个方法,前两个方法是同步的,后两个方法是异步的(从URL获取数据).
伪代码：
- - (void)syncData {
- // Show activity indicator
- [object sync]; // Synchronous method
- [object2 sync]; // Synchronous method
- BOOL object3Synced = [object3 sync]; // Async method
- BOOL object4Synced = [object4 sync]; // Async method
- // Wait for object3 and object4 has finished and then hide activity indicator
- }
我怎样才能做到这一点？
解决方法
假设你实际上有某种方式知道异步方法何时完成,你可能想要的是：
- - (void)syncData {
- // Show activity indicator
- [object sync]; // Synchronous method
- [object2 sync]; // Synchronous method
- _object3Synced = _object4Synced = NO;
- [object3 syncWithCompletionHandler:
- ^{
- _object3Synced = YES;
- [self considerHidingActivityIndicator];
- }]; // Async method
- [object4 syncWithCompletionHandler:
- ^{
- _object4Synced = YES;
- [self considerHidingActivityIndicator];
- }]; // Async method
- }
- - (void)considerHidingActivityIndicator
- {
- if(_object3Synced && _object4Synced)
- {
- // hide activity indicator,etc
- }
- }
