NSControl+Subclasses.m

#import <Cocoa/Cocoa.h>
#import <objc/runtime.h>

@implementation NSControl (Subclasses)

+ (void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        method_exchangeImplementations(class_getInstanceMethod([self class], @selector(initWithCoder:)),
                                       class_getInstanceMethod([self class], @selector(initWithCoder2:)));
    });
}

// Inspired from: http://www.mikeash.com/pyblog/custom-nscells-done-right.html
- (id)initWithCoder2:(NSCoder *)coder
{
    if (![coder isKindOfClass:[NSKeyedUnarchiver class]])
        return [self initWithCoder2:coder];
    NSKeyedUnarchiver * unarchiver = (NSKeyedUnarchiver *)coder;
    Class rootclass = [self superclass];
    while ([NSStringFromClass(rootclass) rangeOfString:@"NS"].location == NSNotFound)
      rootclass = [rootclass superclass];
    Class supercell = [rootclass cellClass];
    Class selfcell = [[self class] cellClass];
    if (!selfcell || !supercell)
        return [self initWithCoder2:coder];
    NSString * supercellName = NSStringFromClass(supercell);
    [unarchiver setClass:selfcell forClassName:supercellName];
    self = [self initWithCoder2:coder];
    [unarchiver setClass:supercell forClassName:supercellName];
    return self;
}

@end