在继续之前,我希望等待此代码执行,但由于这些块是异步调用的,我不知道该怎么做?
NSURL *asseturl;
NSMutableArray *tmpListAsset = [[NSMutableArray alloc] init];
ALAssetsLibrary *library = [[[ALAssetsLibrary alloc] init] autorelease];
NSMutableArray *objectsToRemove = [[NSMutableArray alloc] init];
for (NSDictionary *dico in assetsList) {
asseturl = [NSURL URLWithString:[dico objectForKey:@"assetUrl"]];
NSLog(@"asset url %@", asseturl);
// Try to load asset at mediaURL
[library assetForURL:asseturl resultBlock:^(ALAsset *asset) {
// If asset doesn't exists
if (!asset){
[objectsToRemove addObject:dico];
}else{
[tmpListAsset addObject:[asseturl absoluteString]];
NSLog(@"tmpListAsset : %@", tmpListAsset);
}
} failureBlock:^(NSError *error) {
// Type your code here for failure (when user doesn't allow location in your app)
}];
}
performSelectorInBackground:
),将会发生死锁(因为块被似乎在同一线程上调用,所以信号量永远不会被触发)。请注意避免这种情况。 - alex-i