A subclass of UITableViewCell to allow for images to be added after cell creation

JKTableViewCell.h

#import <UIKit/UIKit.h>


@interface JKTableViewCell : UITableViewCell

@end

JKTableViewCell.m

#import "JKTableViewCell.h"


@implementation JKTableViewCell

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    
    if (self) {
        [[self imageView] addObserver:self
                           forKeyPath:@"image"
                              options:NSKeyValueObservingOptionOld
                              context:NULL];
    }
    
    return self;
}

// The reason we’re observing changes is that if you create a table view cell, return it to the
// table view, and then later add an image (perhaps after doing some background processing), you
// need to call -setNeedsLayout on the cell for it to add the image view to its view hierarchy. We
// asked the change dictionary to contain the old value because this only needs to happen if the
// image was previously nil.
- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    if (object == [self imageView] &&
        [keyPath isEqualToString:@"image"] &&
        ([change objectForKey:NSKeyValueChangeOldKey] == nil ||
         [change objectForKey:NSKeyValueChangeOldKey] == [NSNull null])) {
        [self setNeedsLayout];
    }
}

@end