Hour 18. Extending a Class with Categories and Extensions
What You’ll Learn in This Hour
• Differentiating Categories and Protocols
• Choosing When to Use a Category
• Comparing Categories and Subclasses
• Building and Testing a Category
Comparing Categories and Protocols
In Hour 17, “Extending a Class with Protocols and Delegates,” you saw how to specify a set of methods for a protocol that can be adopted by any class. How the class that adopts the protocol implements it is up to that class: The protocol merely defines the methods that must be (somehow) implemented by the class. Accordingly, when a class adopts a protocol, it can assume that it can call the methods in that protocol.
Categories are somewhat similar to protocols. Instead of being ...
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