Read-only properties of protocols in Swift

Question

From the \"Learn the Essentials of Swift\" playground, there\'s an example protocol:

protocol ExampleProtocol {
    var simpleDescription: String { get }
            


        

Answer 1

There's no way to specify in a protocol that you must have a read-only property. Your protocol asks for a simpleDescription property, and allows but does not require a setter.

Note also that the only reason you may mutate simpleDescription is because you know your a is of type SimpleClass. If we have a variable of type ExampleProtocol instead...

var a: ExampleProtocol = SimpleClass()
a.simpleDescription = "newValue" //Not allowed!