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Swift 协议(protocol)和扩展(extension)

admin

11月 28, 2021

协议

  Swift 使用protocol定义协议:

1 protocol ExampleProtocol {
2     var simpleDescription: String { get }
3     mutating func adjust ()
4 }

类型、枚举和结构都可以实现(adopt)协议:

 1 class SimpleClass: ExampleProtocol {
 2     var simpleDescription: String = "A very simple class." var anotherProperty: Int = 69105
 3     func adjust () {
 4         simpleDescription += " Now 100% adjusted."
 5     }
 6 }
 7 var a = SimpleClass ()
 8 a.adjust ()
 9 let aDescription = a.simpleDescription
10 
11 struct SimpleStructure: ExampleProtocol {
12     var simpleDescription: String = "A simple structure"
13     mutating func adjust () {
14         simpleDescription += " (adjusted)"
15     }
16 }
17 var b = SimpleStructure ()
18 b.adjust ()
19 let bDescription = b.simpleDescription

扩展

  扩展用于在已有的类型上增加新的功能(比如新的方法或属性),Swift 使用extension声明扩展:

1 extension Int: ExampleProtocol {
2     var simpleDescription: String {
3         return "The number (self)"
4     }
5     mutating func adjust () {
6         self += 42
7     }
8 }
9 7.simpleDescription

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