通用類示例

型別引數為 Type 的泛型類

class MyGenericClass<Type>{
 
    var value: Type
    init(value: Type){
        self.value = value
    }
 
    func getValue() -> Type{
        return self.value
    }
 
    func setValue(value: Type){
        self.value = value
    }
}

我們現在可以使用型別引數建立新物件

let myStringGeneric = MyGenericClass<String>(value: "My String Value")
let myIntGeneric = MyGenericClass<Int>(value: 42)
 
print(myStringGeneric.getValue()) // "My String Value"
print(myIntGeneric.getValue()) // 42
 
myStringGeneric.setValue("Another String")
myIntGeneric.setValue(1024)
 
print(myStringGeneric.getValue()) // "Another String"
print(myIntGeneric.getValue()) // 1024

也可以使用多個型別引數建立泛型

class AnotherGenericClass<TypeOne, TypeTwo, TypeThree>{
 
    var value1: TypeOne
    var value2: TypeTwo
    var value3: TypeThree
    init(value1: TypeOne, value2: TypeTwo, value3: TypeThree){
        self.value1 = value1
        self.value2 = value2
        self.value3 = value3
    }
 
    func getValueOne() -> TypeOne{return self.value1}
    func getValueTwo() -> TypeTwo{return self.value2}
    func getValueThree() -> TypeThree{return self.value3}
}

並以同樣的方式使用

let myGeneric = AnotherGenericClass<String, Int, Double>(value1: "Value of pi", value2: 3, value3: 3.14159)
 
print(myGeneric.getValueOne() is String) // true
print(myGeneric.getValueTwo() is Int) // true
print(myGeneric.getValueThree() is Double) // true
print(myGeneric.getValueTwo() is String) // false
 
print(myGeneric.getValueOne()) // "Value of pi"
print(myGeneric.getValueTwo()) // 3
print(myGeneric.getValueThree()) // 3.14159