如何在 Swift 中创建类方法/属性? [英] How do I make class methods / properties in Swift?

问题描述

Objective-C 中的类(或静态)方法是在声明中使用 + 实现的.

Class (or static) methods in Objective-C were accomplished using + in declarations.

@interface MyClass : NSObject

+ (void)aClassMethod;
- (void)anInstanceMethod;

@end

如何在 Swift 中实现这一点?

How can this be achieved in Swift?

推荐答案

它们被称为 类型属性和类型方法并且您使用class 或 static 关键字.

They are called type properties and type methods and you use the class or static keywords.

class Foo {
    var name: String?           // instance property
    static var all = [Foo]()    // static type property
    class var comp: Int {       // computed type property
        return 42
    }

    class func alert() {        // type method
        print("There are \(all.count) foos")
    }
}

Foo.alert()       // There are 0 foos
let f = Foo()
Foo.all.append(f)
Foo.alert()       // There are 1 foos

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