Swift Quick Syntax Reference

Chapter    46

Protocols

When you want to specify properties, methods, and types that would require other types to implement, you can use protocols. A protocol can be adopted by a type. Adopting a protocol means that a type will agree to implement the definition defined in the protocol.

To define a protocol, use the protocol keyword (see Listing 46-1).

Listing 46-1. Defining a Protocol

protocol PrinterProtocol {    func printThis()}

In Listing 46-1, you coded a new protocol named PrinterProtocol, which defined a function named printThis(). If you coded a class that you wanted to adopt this protocol, you would write the code shown in Listing 46-2.

Listing 46-2. Adopting a Protocol

class aClass:PrinterProtocol {}

In Listing 46-2, you defined a ...