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
}
}
