tableViewCell content acts strange - ios

Question

I need some help understanding what may cause my problem in my TableViewCell's content. In my app i use a forum. In the forum we use avatars to the comments/persons. Now I would like to give everyone with name "X" the same avatar. To do so I am trying with the code below but it does not work perfectly and I dont understand why? Sometimes the code bugs and gives for example a person with alias "Y" the "X" alias avatar?
1.First thing I do, is in the storyboard conntect the tag: tableView -> tableViewCell set the UIImageViews tag to 20.
2. Then i run the code below which works in other cases for Alias, Comments in the TableViewCells content.
static NSString *CellIdentifier = #"ForumthreadCell";
UITableViewCell *cell = [pTableView dequeueReusableCellWithIdentifier:CellIdentifier];
ForumPost *x [self.items objectAtIndex:indexPath.row];
UIImageView *pic = (UIImageView *) [cell viewWithTag: 20];
if ([x.alias isEqualsToString:#"X"]){
[pic setImage:[UIImage imagedNamed:#"some picture here.png"]];
}
Any help or suggestions are appreciated. Regards

Answer 1

This is because all the cells in UITableView are reused. That means that your first cell will be reused to load, let's say, your sixth cell. If you don't reload all the elements there and you have image in your first cell, that image will remain in the sixth cell. Another example you could use is to set if indexPath.row == 1 set some property of ForumPost to specific value(after initialization ForumPost *x) and you will have similar behaviour.
To have cells working properly, you need to manage all possible cases.
For instance, you have :
if ([x.alias isEqualsToString:#"X"]){
[pic setImage:[UIImage imagedNamed:#"some picture here.png"]];
}
But you need as well
else if ([x.alias isEqualsToString:#"Y"]){
[pic setImage:[UIImage imagedNamed:#"other pic.png"]];
}
and, if you have other starting names like a, b, c etc.:
else if ([x.alias isEqualsToString:#"Y"]){
[pic setImage:nil];
}