如何在Swift中将类作为参数传递给函数？

Question

让我们考虑一下我有两个不同的班级。

class A {
var something = "Hello"
}

class B {
var something = "World"
}

现在

class C {

func request() {

    //Call with class A or B it can contain any class. I can call either class A or B depending on condition
    update(myClass: A or B)
}

func update(myClass:A or B ) {
    print(myClass.something) //Since both class have same varaible var something so this code should work either i pass class A or B through function
}

}

请使用Swift帮助我实现这一目标

Answer 1

您不能在Swift中声明一个可以接受几种不同类型的输入参数的函数，因此您不能将类型声明为A or B 但是，您实际上不需要此来解决您的特定问题。

由于要访问两个类实例的公共属性，因此应在协议中声明该属性，使两个类均符合该协议，然后使该函数采用协议类型的输入参数。

protocol SomethingProtocol {
    var something: String { get }
}

class A: SomethingProtocol {
    let something = "Hello"
}

class B: SomethingProtocol {
    let something = "World"
}

class C {
    func request() {
        //Call with class A or B it can contain any class. I can call either class A or B depending on condition
        update(something: A())
        update(something: B())
    }

    func update(something: SomethingProtocol) {
        print(something.something) //Since both class have same varaible var something so this code should work either i pass class A or B through function
    }

}

Answer 2

使用协议

protocol MyProtocol: class {
    var something: String { get set }
}

class A: MyProtocol {
    var something = "Hello"
}

class B: MyProtocol {
    var something = "world"
}

class C {
    func update(myClass:MyProtocol ) {
        print(myClass.something) //Since both class have same varaible var something so this code should work either i pass class A or B through function
    }
}

用法：

let a = A()
let b = B()
let c = C()

print(c.update(myClass: a))

print(c.update(myClass: b))

输出：

你好

世界

Answer 3

创建A和B都符合的协议，并将其用作update（）中的参数类型

protocol SomeProtocol {
    var something: String {get set}
}

func update(_ o: SomeProtocol) {
    print(o.something)
}

Answer 4

众所周知，我认为使用protocol是最能解决您问题的最干净的方法。

但是， 可以使用Any传递任何对象作为参数，这将需要检查update方法中要处理的类。

像这样

class C {
    func update(myClass: Any) {
        if let a = myClass as? A {
            print(a.something)
        }
        if let b = myClass as? B {
            print(b.something)
        }
    }
}

switch可能会更整洁- 参考

class C {
    func update(myClass: Any) {
        switch myClass {
        case let a as A:
            print(a.something)
        case let b as B:
            print(b.something)
        default:
            print("not a thing")
        }
    }
}