Update
This doesn't work. The memory for the cell that is returned from dequeueReusableCellWithIdentifier is never released.
If you initialize a cell with a non-nil reuseIdentifier, then that cell will NOT be freed until the tableView itself is released. This is true even if [[tableView valueForKey:@"reusableTableCells"] removeAllObjects] is called. Unfortunately, the tableView is retaining the cell in some other private member and the only way to free it is by destroying the tableView.
Short Answer
The answer to the title of the question of how to clear the tableView cell cache is that Apple does not provide the "ClearReusableCells" functionality, but it is reasonably easy to implement yourself. Simply track the time that the tableView's cache was last cleared and track the time that the cell was created. A cell is considered to be dirty if it was created before the tableView's last cache refresh time.
Alternatives
Steven Canfield's answer - This is a good answer to the specific question, but it does not scale well if there are multiple attributes that can be changed independently of each other. In that case, you can very quickly have lots of 'modes' and that can get unmanageable. Also, with respect to memory usage, it is true that Apple code is responsible for managing the memory, but it is also true that library cannot know when a particular identifier might be needed again, so it will likely end up keeping these cached cells around longer than it needs to.
Recreate the tableView - This is a brute force mechanism that is guaranteed to clear the cell cache. Unfortunately, it is usually inconvenient to recreate the tableView.
Jake's Dahl's answer from the alternate question - This is a good mechanism for clearing the cache that probably worked at the time it was written, but it relies on some implementations that Apple does not guarantee, and that have, in fact, already changed.
Implementation
There are multiple ways of tracking the tableView's cache refresh time and the cell creation time. I've shown a mechanism below that uses subclasses. Of course, for this to work, you need to make sure that the code that instantiates the table and cells instantiates the subclasses.
@interface MyTableView : UITableView
@property(nonatomic,assign) NSTimeInterval cellCacheRefreshTime ;
@end
@interface MyTableViewCell : UITableViewCell
@property(nonatomic,assign) NSTimeInterval creationTime ;
@end
@implemetation MyTableView
-(void) refreshCellCache {
self.cellCacheRefreshTime = [NSDate timeIntervalSinceReferenceDate];
}
- (id)dequeueReusableCellWithIdentifier:(NSString *)identifier {
MyTableViewCell *cell = (id)[super dequeueReusableCellWithIdentifier:identifier] ;
if( cell.creationTime < aTableView.cellCacheRefreshTime ) {
return nil ;
}
return cell ;
}
@end
@implemetation MyTableViewCell
-(instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier] ;
self.creationTime = [NSDate timeIntervalSinceReferenceDate];
return self ;
}
@end
