swift - 如何声明以函数为值并以整数为键的字典？

struct Test {
    func isOk () -> Bool{
        return true
    }

    var mapping: [Int: () -> Bool] = [
        1: isOk
    ]

    func test() -> Bool {
        return mapping[1]()
    }
}

我收到此错误:

Cannot convert value of type '(Test) -> () -> Bool' to expected dictionary value type '() -> Bool'

任何想法？谢谢!

最佳答案

您会看到这种奇怪的类型((Test) -> () -> Bool)，因为Swift instance methods are curried functions。

如果可以将isOk设为静态方法，则可以执行以下操作:

struct Test {
    static func isOk() -> Bool { //Make it static
        return true
    }

    var mapping: [Int : () -> Bool] = [
        1 : Test.isOk // Static method must be qualified by its parent type
    ]

    func test() -> Bool { //Bool return value necessary
        //TODO: remove force unwrapping.
        return mapping[1]!() //subscripting a Dict might return nil
    }
}

如果isOk必须保留为实例方法，则可以执行以下操作:

struct Test {
    func isOk() -> Bool {
        return true
    }

    var mapping: [Int : (Test) -> () -> Bool] = [ //change type
        1 : isOk
    ]

    //the instance method received from the dict needs an instance to act on
    func test(instance: Test) -> Bool { //Bool return value necessary
        //TODO: remove force unwrapping.
        return mapping[1]!(instance)() //curried function call
    }
}