既存クラスのメソッドを入れ替える(Method Swizzling) ref: http://qiita.com/paming/items/25eaf89e4f448ab05752

AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    [UIViewController switchLoggingMethod];  // ←これでメソッドが入れ替わる
    return YES;
}

UIViewController+MethodSwitch.h

#import <UIKit/UIKit.h>
@interface UIViewController(MethodSwitch)
+(void)switchLoggingMethod;
@end

UIViewController+MethodSwitch.m

#import "UIViewController+MethodSwitch.h"
#import <objc/runtime.h>

@implementation UIViewController(MethodSwitch)

// 入れ替えるメソッドを準備
-(void)loggingViewDidLoad
{
    NSLog(@"%@ viewDidLoad",NSStringFromClass(self.class));
    [self loggingViewDidLoad];  // ここ、無限ループしそうだけど、メソッドの実装が入れ替わるので、元々あったviewDidLoadの実装が呼ばれます。
}
-(void)loggingViewWillAppear:(BOOL)animated{
    NSLog(@"%@ viewWillAppear",NSStringFromClass(self.class));
    [self loggingViewWillAppear:animated];
}
-(void)loggingViewDidAppear:(BOOL)animated{
    NSLog(@"%@ viewDidAppear",NSStringFromClass(self.class));
    [self loggingViewDidAppear:animated];
}
-(void)loggingViewWillDisappear:(BOOL)animated{
    NSLog(@"%@ viewWillDisappear",NSStringFromClass(self.class));
    [self loggingViewWillDisappear:animated];
}
-(void)loggingViewDidDisappear:(BOOL)animated{
    NSLog(@"%@ viewDidDisappear",NSStringFromClass(self.class));
    [self loggingViewDidDisappear:animated];
}

+(void)switchLoggingMethod
{
    // メソッドを入れ替える
    [self switchInstanceMethodFrom:@selector(viewDidLoad)        To:@selector(loggingViewDidLoad)       ];
    [self switchInstanceMethodFrom:@selector(viewWillAppear:)    To:@selector(loggingViewWillAppear:)   ];
    [self switchInstanceMethodFrom:@selector(viewDidAppear:)     To:@selector(loggingViewDidAppear:)    ];
    [self switchInstanceMethodFrom:@selector(viewWillDisappear:) To:@selector(loggingViewWillDisappear:)];
    [self switchInstanceMethodFrom:@selector(viewDidDisappear:)  To:@selector(loggingViewDidDisappear:) ];
}

+(void)switchInstanceMethodFrom:(SEL)from To:(SEL)to
{
    // メソッドの入れ替えの実態はここ
    Method fromMethod = class_getInstanceMethod(self,from);
    Method toMethod   = class_getInstanceMethod(self,to  );
    method_exchangeImplementations(fromMethod, toMethod);
}
@end