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SwiftLee > Swift > Optional protocol methods in Swift

Swift Mar 18, 2016Jul 12, 2019 • < 1

Optional protocol methods in Swift

In Swift it’s kind of unsupported to implemented optional protocol methods.

You can, which is ugly, use the @objc syntax:

@objc protocol MyProtocol {
    optional func doSomething();
}

class MyClass : MyProtocol {
    // no error
}

Another disadvantage here is that structs are unsupported, as you’re bridging for Objc.

Using protocol extensions to create optional protocol methods

However, with Swift 2.0 it’s possible to define protocol extension. This allows you to create optional methods for your protocol easily:

protocol MyProtocol {
    func doSomethingNonOptionalMethod()
    func doSomethingOptionalMethod()
}

extension MyProtocol {
    func doSomethingOptionalMethod(){ 
        // leaving this empty 
    }
}

As stated in this thread, many people are asking this feature:
http://stackoverflow.com/questions/24032754/how-to-define-optional-methods-in-swift-protocol