Sharing assets across iOS projects with CocoaPods, Resource Bundle, and dynamically loaded fonts

It is useful and time saving to centralize all the resources, assets and fonts that are shared across different projects. The best solution for that is CocoaPods, and a bit of code to avoid doing any kind on Info.plist update.

If you can't be bothered reading the post, and want to look at some code straightaway checkout this example I've made.

The process is very simple:

Create the pod
Add the resources to the pod resource bundle
Dynamically load the fonts

Creating a pod is super simple, I already wrote about it, but it was a while ago, the best place to look for it is the official CocoaPod documentation.

Add the assets to the pod resource bundle

Since version 0.23.0 the Spec DSL has a resource_bundle attribute, and it's recommended to use it instead of the old resources, to avoid potential name clashes with other pods or libraries.

But what's a resource bundle? As usual the Apple Documentation is not very clear, but we could define a bundle as a folder with an extension, conforming to some rules for it's content.

Then how do we make a bundle? Or in our case a Resource Bundle, so that we can add it in our .podspec? As you can imagine the Documentation is still not helpful...

I spent a couple of hours messing around creating folders naming the folder.bundle, googling and stackoverflowing, but with no luck integrating it with my pod. I also found a tutorial by Matt Galloway, but it looked like a complex hack, there had to be something simpler!

Turns out it's dead simple! Just list the resources path you want in the bundle and the pod will generate it for you. Boom. No tricks, no hacks, just a line of code.

spec.ios.resource_bundle = { 'MapBox' => 'MapView/Map/Resources/*.png' }

Dynamically load the fonts

Now that the we have our Resource Bundle ready we only need to skip the annoying process of adding the fonts to the Info.plist and we're good to go.

To do that I used the approach suggested by Marco Armet in this blog post. It's possible to dynamically load fonts and then consume them with the usual fontNamed:withSize UIFont class method.

NSData *inData = /* your decrypted font-file data */;
CFErrorRef error;
CGDataProviderRef provider = CGDataProviderCreateWithCFData((CFDataRef)inData);
CGFontRef font = CGFontCreateWithDataProvider(provider);
if (! CTFontManagerRegisterGraphicsFont(font, &error)) {
    CFStringRef errorDescription = CFErrorCopyDescription(error)
    NSLog(@"Failed to load font: %@", errorDescription);
    CFRelease(errorDescription);
}
CFRelease(font);
CFRelease(provider);

The only downside of this approach is that we need to run that code at some point. I put it into a FontsManager class, with getters for the fonts that sort of lazy loads them. Like this:

static NSString * const kBundle = @"ResourceBundle.bundle";

+ (UIFont *)openSansLightFontOfSize:(CGFloat)size
{
    NSString *fontName = @"OpenSans-Light";
    UIFont *font = [UIFont fontWithName:fontName size:size];
    if (!font) {
        [[self class] dynamicallyLoadFontNamed:fontName];
        font = [UIFont fontWithName:fontName size:size];

        // safe fallback
        if (!font) font = [UIFont systemFontOfSize:size];
    }

    return font;
}

+ (void)dynamicallyLoadFontNamed:(NSString *)name
{
    NSString *resourceName = [NSString stringWithFormat:@"%@/%@", kBundle, name];
    NSURL *url = [[NSBundle mainBundle] URLForResource:resourceName withExtension:@"ttf"];
    NSData *fontData = [NSData dataWithContentsOfURL:url];
    if (fontData) {
        CFErrorRef error;
        CGDataProviderRef provider = CGDataProviderCreateWithCFData((CFDataRef)fontData);
        CGFontRef font = CGFontCreateWithDataProvider(provider);
        if (! CTFontManagerRegisterGraphicsFont(font, &error)) {
            CFStringRef errorDescription = CFErrorCopyDescription(error);
            NSLog(@"Failed to load font: %@", errorDescription);
            CFRelease(errorDescription);
        }
        CFRelease(font);
        CFRelease(provider);
    }
}

What about the images?

We can access images with the same strategy used for the fonts, a manager that lazy loads them from the bundle.

Having a tidy project is invaluable, specially when it only needs a couple of lines of code. Plus by grouping our assets in a pod we can quickly implement other apps with a style consistent to our branding.

If you're interested in the matter of handling big projects by modularizing them, this article will be an interesting read.

Leave your codebase better than you found it

mokacoding