Picking an item of NSArray using key value coding

Question

If you read listing 4 in the Animation section Apple's Core Animation guide, it seems to use KVC and the key path "filters.pulseFilter.inputIntensity" to pick out an object called "pulseFilter" out of an NSArray. "pulseFilter" is actually a CIFilter named "pulseFilter" by calling the method setName.

Now, I don't see the method setName defined anywhere. I also don't believe you can select a specific item out of an NSArray by using a key. Can someone explain how this works?

Answer 1

It does not necessarily have to go through standard valueForKey: or valueForKeyPath: of the NSArray.

Objects are free to provide own valueForKeyPath: method and handle KVC its own way and this is what probably the class of this selectionLayer object does.

Answer 2

To retrieve an object from NSArray using a property name + property value. Step 1: get your stored object compliant to KVC (NSKeyValueCoding protocol) by implementing valueForKey: in your custom class.

Step 2: filter your NSArray using NSPredicate (filteredArrayUsingPredicate on your NSArray)

Do you need more detail ?