Cocoa Programming for OS X: The Big Nerd Ranch Guide

For the More Curious: Key Paths

Objects are often arranged in a network. For example, a person might have a spouse who has a scooter that has a model name (Figure 8.14).

Figure 8.14  Directed graph of objects

To get the selected person’s spouse’s scooter’s model name, you can use a key path:

l​e​t​ ​m​o​d​e​l​N​a​m​e​ ​=​ ​s​e​l​e​c​t​e​d​P​e​r​s​o​n​.​v​a​l​u​e​F​o​r​K​e​y​P​a​t​h​(​"​s​p​o​u​s​e​.​s​c​o​o​t​e​r​.​m​o​d​e​l​N​a​m​e​"​)​ ​a​s​ ​S​t​r​i​n​g​

We would say that spouse and scooter are relationships of the Person class and that modelName is an attribute of the Scooter class.

There are also operators that you ...