🗃  NSObject+Traversal-ObjC

Language: Objective-C

Foundation and its support for Key-Value Coding is great for setting and getting values on NSDictionaries at a key path address like key.subkey. But KVC falls short when you need to reach into or through an NSArray which is embedded within a dictionary.

For that reason we created a category on NSObject which adds support for setting and getting values at enhanced, "rich" keypaths, so that if you have an MSMutableDictionary dictionary like this:

NSMutableDictionary *dictionary = [NSMutableDictionary new];
{
	NSMutableArray *array = [NSMutableArray new];
	{
		NSMutableDictionary *nestedDictionary = [NSMutableDictionary new];
		{
			nestedDictionary[@"subkey"] = aValue;
		}
		[array addObject:nestedDictionary];
	}
	dictionary[@"key"] = array;
}

you can do stuff like this:

id theValue = [dictionary valueForRichKeyPath:@"key.0.subkey"];

and this:

[dictionary setValue:anotherValue forAndHydrateRichKeyPath:@"key.0.subkey"];

Isn't that cool?

The above method -setValue:forAndHydrateRichKeyPath: will even fill in the necessary collection objects if necessary while traversing the key path, in order to be able to set the value at the leaf – much like mkdir -p.

Installation

To install, download the source or add this repo as a submodule, and drag ./NSObject+Traversal into your Xcode project.

Usage

NSObject+Traversal.h exposes the following two methods for rich key path operations:

- (id)valueForRichKeyPath:(NSString *)keyPath;
- (void)setValue:(id)value forAndHydrateRichKeyPath:(NSString *)keyPath;

It also provides the following internally used accessors for convenience:

- (LPObjectType)objectType; // Detects whether the object is a dictionary, array, primitive, or other type	
- (BOOL)isMutable; // Implements the various -respondsToSelector: checks for mutability