Objective-C Programming: The Big Nerd Ranch Guide

35 Key-Value coding

Key-value coding is the ability to read and set a property using its name. The key-value coding methods are defined in NSObject, and thus every object has this capability.

Open main.m and find the line:

 ​ ​ ​ ​[​a​ ​s​e​t​P​r​o​d​u​c​t​N​a​m​e​:​@​"​W​a​s​h​i​n​g​ ​M​a​c​h​i​n​e​"​]​;​

Rewrite the same line to use key-value coding:

 ​ ​ ​ ​[​a​ ​s​e​t​V​a​l​u​e​:​@​"​W​a​s​h​i​n​g​ ​M​a​c​h​i​n​e​"​ ​f​o​r​K​e​y​:​@​"​p​r​o​d​u​c​t​N​a​m​e​"​]​;​

In this case, the setValue:forKey: method, as defined in NSObject, will go looking for a setter method named setProductName:. If the object does not have a setProductName: method, it will access the instance variable directly.

You can also read the value of ...