[Swift] KeyPath, WritableKeyPath, ReferenceWritableKeyPath 차이와 구분해서 사용하기

 

GitHub - insub4067/KeyPath--WritableKeyPath--ReferenceWritableKeyPath

protocol SelfReturnable {
    associatedtype ReturnType
    func with<T>(_ keyPath: WritableKeyPath<Self, T>, _ value: T) -> ReturnType
}

extension SelfReturnable {
    func with<T>(_ keyPath: WritableKeyPath<Self, T>, _ value: T) -> Self {
        var copy = self
        copy[keyPath: keyPath] = value
        return copy
    }
}

protocol RefSelfReturnable {
    associatedtype ReturnType
    func with<T>(_ keyPath: ReferenceWritableKeyPath<Self, T>, _ value: T) -> ReturnType
}

extension RefSelfReturnable {
    func with<T>(_ keyPath: ReferenceWritableKeyPath<Self, T>, _ value: T) -> Self {
        let copy = self
        copy[keyPath: keyPath] = value
        return copy
    }
}

struct ValueItem: SelfReturnable {
    let name: String
    var age: Int
}


final class RefItem: RefSelfReturnable {
    let name: String
    var age: Int
    
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
}


let valueItem = ValueItem(name: "kim", age: 1)
let refItem = RefItem(name: "lee", age: 2)

let newValueItem = valueItem.with(\.age, 11)
let newRefItem = refItem.with(\.age, 12)

dump(newValueItem)
dump(newRefItem)

결론 ->

ReferenceWritableKeyPath은 클래스에 사용하면 됨

하지만 그렇다고 WritableKeyPath 를 클래스에 사용하지 못하는게 아님.

var 로 선언된 변수에는 다 사용가능.

일반적으로 단순히 접근하는 경우는 KeyPath를 사용해도 상관 없음