Fail Fast and assert when [UIImage imageNamed:name] cannot load an image

UIImage+FailFast.h

//
//  UIImage+FailFast.h
//
//  Created by Jason Jarrett on 2/11/15.
//  Copyright (c) 2015 Jason Jarrett. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIImage (FailFast)
@end

UIImage+FailFast.m

//
//  UIImage+FailFast.m
//
//  Created by Jason Jarrett on 2/11/15.
//  Copyright (c) 2015 Jason Jarrett. All rights reserved.
//

// Let's only use this in a DEBUG/developer mode
#if DEBUG

#import "UIImage+FailFast.h"
#import "objc/runtime.h"

static Method origImageNamedMethod = nil;
static NSArray *imagesAllowedToBeMissing;

@implementation UIImage (FailFast)

+ (void)load {

    // Swizzle the core [UIImage imageNamed:name] selector with our custom selector
    origImageNamedMethod = class_getClassMethod (self, @selector (imageNamed:));
    method_exchangeImplementations (origImageNamedMethod, class_getClassMethod (self, @selector (assertIfImageNamedNotFound:)));

    static dispatch_once_t onceToken;
    dispatch_once (&onceToken, ^{
        // Setup a colleciton of images that may be missing but are allowed to be nil
        imagesAllowedToBeMissing = @[
                                     // TODO: if any images are OK missing - add them here
                                     // @"",
                                     ];
    });
}

+ (UIImage *)assertIfImageNamedNotFound:(NSString *)name {
    NSLog (@"Loading image named: %@", name);

    // This will call the original core imageNamed selector which actually loads the image
    UIImage *image = [self assertIfImageNamedNotFound:name];

    if ([imagesAllowedToBeMissing indexOfObject:name] == NSNotFound) {
        NSAssert (image != nil, @"Failed to load imageNamed: %@", name);
    }

    return image;
}

@end

#endif