Objective-c block synchronizing data - objective-c

Question

I'm developing a program that gets feed from Instagram. I'm really new to objective-c so please be patient with my question. I have a button that calls a method to get the feeds, but it is a block so when the method finishes sometimes the block still continues loading images. The problem occurs when I change the user. I clear the media array but the method fired fills the array with old user data. I tried to use a property userchanged but it seems that it cancels the current user data too. How should I synchronize these methods? I can't figure it out.
#property (nonatomic, copy) NSMutableArray *mediaArray;
#property (nonatomic, assign) BOOL currentUserChanged;
- (void)getInstagramSelfFeed
{
if (self.currentPaginationInfo.nextMaxId != self.requestedPaginationInfo)
{
self.requestedPaginationInfo = self.currentPaginationInfo.nextMaxId;
[[InstagramEngine sharedEngine] getSelfFeedWithCount:15 maxId:self.currentPaginationInfo.nextMaxId success:^(NSArray *media, InstagramPaginationInfo *paginationInfo){
self.currentPaginationInfo = paginationInfo;
if ([self checkIfCurrentUserChanged])
{
return;
}
[self.mediaArray addObjectsFromArray:media];
[[NSNotificationCenter defaultCenter] postNotificationName:#"finishGettingSelfFeed" object:self];
} failure:^(NSError *error) {
NSLog(#"Request Self Feed Failed %#", error);
}];
}
}
- (void)setCurrentUser:(User *)currentUser
{
if (_currentUser != currentUser)
{
_currentUser = currentUser;
[[InstagramEngine sharedEngine] setAccessToken:self.currentUser.accessToken];
[self.mediaArray removeAllObjects];
if ([self.currentViewController isKindOfClass:[TimelineViewController class]])
{
self.currentUserChanged = YES;
}
MenuController *menuController = [MenuController sharedManager];
[menuController updateAllViews];
}
}
- (User *)currentUser
{
return _currentUser;
}
- (BOOL)checkIfCurrentUserChanged
{
if (self.currentUserChanged)
{
self.currentUserChanged = false;
return YES;
}
return NO;
}

Answer 1

OK, I solved the problem. Now I'm sending the user that made the request and compare both.
- (void)getInstagramSelfFeed: (User *)user
{
if (self.currentPaginationInfo.nextMaxId != self.requestedPaginationInfo)
{
self.requestedPaginationInfo = self.currentPaginationInfo.nextMaxId;
self.executingGetSelfFeed = true;
[[InstagramEngine sharedEngine] getSelfFeedWithCount:15 maxId:self.currentPaginationInfo.nextMaxId success:^(NSArray *media, InstagramPaginationInfo *paginationInfo){
self.currentPaginationInfo = paginationInfo;
if (user != self.currentUser)
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"gettingSelfFeedCancelled" object:self];
return;
}
[self.mediaArray addObjectsFromArray:media];
[[NSNotificationCenter defaultCenter] postNotificationName:#"finishGettingSelfFeed" object:self];
} failure:^(NSError *error) {
NSLog(#"Request Self Feed Failed %#", error);
}];
}
}

Answer 2

A big problem is that you have a mutable array, and it is a "copy" property. That's just wrong. When you access self.mediaArray, a copy of the instance variable is made, and then you modify the copy. The instance variable itself is never modified.