Programming in Objective-C, Sixth Edition

Manual Reference Counting

If you are going to create applications without the use of garbage collection or ARC, or if you have to support code that you can’t migrate to run with ARC, then you need to know how to manage memory. That is, you need to learn about how to work with reference counts.

The general concept is as follows: When an object is created, its initial reference count is set to 1. Each time you need to ensure that the object be kept around, you effectively create a reference to it by incrementing its reference count by 1. This is done by sending the object a retain message, like so:

[myFraction retain];

When you no longer need an object, you decrement its reference count by 1 by sending it a release message, like this:

[myFraction ...