问题

## 免责声明
请注意，这只是一个简化的示例。实际问题稍微复杂，所以我需要一个实际的数组扩展而不是其他解决方案。
我知道
```swift
let mapped: [MyGeneric<Int>] = items.map { .init(someVariable: $0) }

会起作用，但我正在寻找一种编写通用数组扩展的方法，而不是修复这个简化的代码

问题

我正在尝试编写如下的通用数组/集合扩展：

struct MyGeneric<T: Hashable> {
    let someVariable: T
}

期望的输出

下面的代码不起作用，因为我缺少Array扩展，但理想情况下，我的输出应该类似于这样：

let items: [Int] = [1, 2, 3, 4, 5]
let mapped: [MyGeneric<Int>] = .init(items)

所以我需要的是：

extension [MyGeneric<Hashable>] {
    init(someArray: [some Hashable]) {
        self = someArray.map { MyGeneric(someVariable: $0)}
    }
}

但当然，这不会编译，因为扩展中的通用参数没有传递到初始化通用参数。我如何将扩展中的类型传递给其中的函数。我能在这个函数中以某种方式使用 Element.Type 并从中提取通用类型吗？或者也许有一种 extension Array where ... 语法，我不太熟悉？

<details>
<summary>英文:</summary>

## Disclaimer
Please note this is only a simplified example. Actual problem is a bit more complex so I need actual Array extension rather than other solution.
I know that
```swift
let mapped: [MyGeneric&lt;Int&gt;] = items.map { .init(someVariable: $0) }

will work, but I'm looking for a way to write generic array extension not fix this simplified code

Problem

I'm trying to write a generic extension to an array/collection as below:

struct MyGeneric<T: Hashable> {
	let someVariable: T
}

Expected output

Code below is not working because I'm missing Array extension, but ideally my output would be something like this:

let items: [Int] = [1, 2, 3, 4, 5]
let mapped: [MyGeneric<Int>] = .init(items)

So what I need is:

extension [MyGeneric<Hashable>] {
	init(someArray: [some Hashable]) {
		self = someArray.map { MyGeneric(someVariable: $0)}
	}
}

but of course this is not compiling because generic parameter from extension is not passed to init generic parameter. How can I pass the type from extension to functions in that. Can I use somehow Element.Type in this one and extract Generic type from there? Or maybe there is an extension Array where ... syntax that I'm not familiar with?

答案1

得分: 2

受到@MartinR提供的答案启发，我想出了以下解决方案

extension Array {
    init<T>(_ array: [T]) where Element == MyGeneric<T> {
        self.init(array.map(MyGeneric.init))
    }
}

extension Array {
    init<T>(_ array: [T]) where Element == MyGeneric<T> {
        self.init(array.map(MyGeneric.init))
    }
}