Class Cluster example as described here - http://www.noxeos.com/2013/06/18/strategies-support-ios7-ui/

ClassCluster.m

@interface MyView : UIView
- (void)kissMyAss;
@end

@interface _MyViewIOS6 : MyView
@end

@interface _MyViewIOS7 : MyView
@end

@implementation MyView

BOOL isIOS7 = YES; // This would be a function somewhere

+ (id)alloc {
    if([self class] == [MyView class]) {
        if(isIOS7) {
            return [_MyViewIOS7 alloc];
        }
        else {
            return [_MyViewIOS6 alloc];
        }
    }

    return [super alloc];
}

- (void)kissMyAss {}

// Test method
+ (void)testClassCluster {
    MyView *myView = [[MyView alloc] init];
    [myView kissMyAss];
}

@end

@implementation _MyViewIOS6

- (void)kissMyAss {
    NSLog(@"iOS 6 can kiss my ass");
}

@end

@implementation _MyViewIOS7

- (void)kissMyAss {
    NSLog(@"iOS 7 can kiss my ass");
}

@end