It’s been a while since my last post. I’ve been busy settling into my new life as a freelancer out of Frankfurt. I’m happy to be here, although I do miss New York a lot. I’ve been busy lately looking for clients (drop me a line if you require some iOS craftsmanship), and with small projects of my own.

For my upcoming app, I recently forked two neat components and made them configurable through an options dictionary. I ended up with a nice drop-in solution for optional options (no pun intended) backed up by default values.

What I wanted

• With KNSemiModalViewController, view controllers can present other view controllers that cover the screen only partially. I wanted to be able to tweak the animation duration, shadow, dimming, and whether a visual push-back effect should be used during the transition.

• DerpKit allows view controllers to resize their root view when the keyboard becomes visible. Since I wanted to use this feature on my semi-modal view controller, with a view merely 88pt high, I needed to enforce a minimum height so that the semi-modal view would be pushed up, instead of covered, by the keyboard.

What I did (at first)

I extended the API with some additional methods that take an options parameter, e.g.:

• -[UIViewController derp_addKeyboardViewHandlersWithOptions:]
• -[UIViewController presentSemiViewController:withOptions:completion:]

Next, I had a number of smelly, repetitive code snippets that all looked like this:

#define kYMShadowOpacity 0.3
- (id) shadowOpacityOptionOrDefault {
	NSDictionary *options = objc_getAssociatedObject(self, @"YMOptions"));
	return options[@"ym_ShadowOpacity"] ?: kYMShadowOpacity;
}

Brrr… there had to be a better way.

An extensible re-usable solution

Here’s the gist: Register options and defaults once, then use an “option or default” method and pass in the key you are interested in.

Or rather, here’s the gist:

#import <objc/runtime.h>

- (void)ym_registerOptions:(NSDictionary *)options
				  defaults:(NSDictionary *)defaults
{
	objc_setAssociatedObject(self, @"YMOptions", options, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
	objc_setAssociatedObject(self, @"YMDefaults", defaults, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (id)ym_optionOrDefaultForKey:(NSString*)optionKey
{
	NSDictionary *options = objc_getAssociatedObject(self, @"YMOptions"));
	NSDictionary *defaults = objc_getAssociatedObject(self, @"YMDefaults"));
	return options[optionKey] ?: defaults[optionKey];
}

You get a drop-in NSObject category in my YMFoundationAdditions repo, along with other handy stuff. They are also included in my DerpKit and KNSemiModalViewController forks.

Let me know what you think on Twitter or App.net. Have a great day!