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 setProductName:@"Washing Machine"];

Rewrite the same line to use key-value coding:

    [a setValue:@"Washing Machine" forKey:@"productName"];

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 a variable using key-value coding. Add a line to main.m that prints out the product name:

int main (int ...