I have a view controller with a table view. in each cell of the table view, i have an image which is fetched from the net - but many of them have the same image. so, what i'm doing currently is storing the fetched images in a NSCache object. it happens this way:
- (void)fetchAvatarForUser:(NSString *)uid completion:(void (^)(BOOL))compBlock
{
if (!imageCache) {
imageCache = [[NSCache alloc] init];
}
if (!avatarsFetched) {
avatarsFetched = [[NSMutableArray alloc] initWithCapacity:0];
}
if ([avatarsFetched indexOfObject:uid] != NSNotFound) {
// its already being fetched
} else {
[avatarsFetched addObject:uid];
NSString *key = [NSString stringWithFormat:@"user%@",uid];
NSString *path = [NSString stringWithFormat:@"users/%@/avatar",uid];
[crudClient getPath:path parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(@"%@",[operation.response allHeaderFields]);
UIImage *resImage = [UIImage imageWithData:[operation responseData]];
[imageCache setObject:resImage forKey:key];
compBlock(YES);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"Got error: %@", error);
compBlock(NO);
}];
}
}
- (UIImage *)getAvatarForUser:(NSString *)uid
{
NSString *key = [NSString stringWithFormat:@"user%@",uid];
NSLog(@"Image cache has: %@",[imageCache objectForKey:key]);
return [imageCache objectForKey:key];
}
imageCache is an instance variable, and also avatarsFetched, crudClient is an AFHTTPClient object. and, in the table view:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
PostCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[PostCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
Post *curPost = [displayedPosts objectAtIndex:indexPath.section];
cell.nickname.text = [curPost nickname];
UIImage *avatarImage = [self.delegateRef.hangiesCommunicator getAvatarForUser:curPost.userID];
if (avatarImage) {
cell.avatar.image = avatarImage;
NSLog(@"Its not null");
} else {
cell.avatar.image = [UIImage imageNamed:@"20x20-user-black"];
}
}
self.delegateRef.hangiesCommunicator returns the object (which is a retained property of the app delegate) with the imageCache as an instance variable, and the two methods at the top.
When i scroll, i see the @"Its not null" in the console, yet i don't see the fetched image but the default 20x20-user-black image. does anybody have an idea, why is this happening? what am i doing wrong?
thanks!
Your code is missing some things. I can't see where you ever call the fetchAvatarForUser:completion: method on your hangiesCommunicator and your tableView:cellForRowAtIndexPath: method is not returning the cell, so I don't think the code you posted will compile cleanly.