Swift Property WrappersInitialization 失败并显示无法将‘Double’类型的值转换为预期的参数类型

我把自己变成了一个playground --熟悉房产包装的榜样.

以下代码:

import Foundation

@propertyWrapper
struct Price {
    private var price: Double
    
    init() {
        self.price = 0.0
    }
    
    var wrappedValue: Double {
        get {
            return self.price
        }
        set {
            if newValue < 0.0 {
                self.price = 0.0
            } else if newValue > 10_000 {
                return
            } else {
                self.price = newValue
            }
        }
    }
}

struct Article {
    var vendor: String
    var name: String
    @Price var price: Double
}

var display = Article(vendor: "Asus", name: "X127", price: 139.0)
/*
 expression failed to parse:
 error: Playground.playground:33:60: error: cannot convert value of type 'Double' to expected argument type 'Price'
 var display = Article(vendor: "Asus", name: "X127", price: 139.0)
 */
print("\(display.vendor) Display costs \(display.price) Euro")

如果我用...

var display = Article(vendor: "Asus", name: "X127")
display.price = 129.99
print("\(display.vendor) Display costs \(display.price) Euro")
// Asus Display costs 129.99 Euro

...那么它就运行得很好.

What I'm I doing wrong with the constructor-initialization? What's the correct way to initialize the wrapper property?个

What is going wrong within the first example in general?个