Swift筆記：Protocols and Extensions

使用protocol宣告協議。

protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust()
}

class、enum和struct都可以實現protocol。

class的實現：

class SimpleClass: ExampleProtocol {
    var simpleDescription: String = "A very simple class."
    var anotherProperty: Int = 69105
    func adjust() {
        simpleDescription += "  Now 100% adjusted."
    }
}
var a = SimpleClass()
a.adjust()
let aDescription = a.simpleDescription

struct的實現：

struct SimpleStructure: ExampleProtocol {
    var simpleDescription: String = "A simple structure"
    mutating func adjust() {
        simpleDescription += " (adjusted)"
    }
}
var b = SimpleStructure()
b.adjust()
let bDescription = b.simpleDescription

使用extension擴展現有class的功能，例如新的方法和參數。

extension Int: ExampleProtocol {
    var simpleDescription: String {
    return "The number \(self)"
    }
    mutating func adjust() {
        self += 42
    }
}