Example for how to set up a UIAppearance proxy specific to one controller in Swift

AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

  var window: UIWindow?

  func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    UIButton.appearanceProxyIn(ViewController).backgroundColor = UIColor.redColor()
    UIButton.appearanceProxyIn(ViewController).tintColor = UIColor.yellowColor()
    UIButton.appearance().tintColor = UIColor.blackColor()
    return true
  }
}

UIView+Appearance.h

#import <UIKit/UIKit.h>

@interface UIView(Appearance)
+(instancetype)appearanceProxyIn:(Class)klass;
@end

UIView+Appearance.m

#import "UIView+Appearance.h"

@implementation UIView(Appearance)

+(instancetype)appearanceProxyIn:(Class)klass {
    return [self appearanceWhenContainedIn:klass, nil];
}

@end