UIViewController+ClassNameOverlay

AppDelegate.m

#ifdef DEBUG
#import "UIViewController+ClassNameOverlay.h"
#endif

UIViewController+ClassNameOverlay.h

#import <UIKit/UIKit.h>

@interface UIViewController (ClassNameOverlay)

@end

UIViewController+ClassNameOverlay.m

#import "UIViewController+ClassNameOverlay.h"

#import <objc/runtime.h>

@implementation UIViewController(ClassNameOverlay)

+ (void)load
{
    // http://nshipster.com/method-swizzling/
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        SEL originalSelector = @selector(viewWillAppear:);
        SEL swizzledSelector = @selector(cno_viewWillAppear:);
        
        Class class = [self class];
        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
        
        BOOL didAddMethod =
        class_addMethod(class,
                        originalSelector,
                        method_getImplementation(swizzledMethod),
                        method_getTypeEncoding(swizzledMethod));
        
        if (didAddMethod) {
            class_replaceMethod(class,
                                swizzledSelector,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

- (void)cno_viewWillAppear:(BOOL)animated
{
    [self cno_viewWillAppear:animated];
    
    UIColor *color = [self randomColor];
    
    UILabel *classNameLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, self.view.frame.size.width, 44)];
    classNameLabel.text = NSStringFromClass([self class]);
    classNameLabel.numberOfLines = 0;
    classNameLabel.font = [UIFont boldSystemFontOfSize:14];
    classNameLabel.textColor = color;
    
    classNameLabel.backgroundColor = [UIColor colorWithRed:1 green:1 blue:1 alpha:0.8];
    
    if ([classNameLabel.text hasPrefix:@"UI"]) {
        classNameLabel.hidden = YES;
    } else {
        self.view.layer.borderWidth = 5;
        self.view.layer.borderColor = color.CGColor;
    }
    
    [self.view addSubview:classNameLabel];
}

- (UIColor *)randomColor
{
    // https://gist.github.com/r3econ/9772706
    CGFloat hue = ( arc4random() % 256 / 256.0 );
    CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5;
    CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5;
    return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
}

@end

example1.png

example2.png