ios - 在我们的 Swift 文件中，我在哪里导入 swift 模块？

Question

我正在阅读 Matt 的 iOS 编程书，当我读到这里时:

Swift itself is defined in a module — the Swift module. Your code always implicitly imports the Swift module. You could make this explicit by starting a file with the line import Swift; there is no need to do this, but it does no harm either.

That fact is important, because it solves a major mystery: where do things like print come from, and why is it possible to use them outside of any message to any object? print is in fact a function declared at the top level of the Swift module, and your code can see the Swift module’s top-level declarations because it imports Swift. The print function thus becomes, as far as your code is concerned, an ordinary top-level func‐ tion like any other; it is global to your code, and your code can speak of it without specifying its namespace. You can specify its namespace — it is perfectly legal to say things like Swift.print("hello") — but you probably never will, because there’s no name conflict to resolve.

例如，在我的测试中ViewController:

import UIKit
//import Swift // here we can import Swift. it is okay

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    
        Swift.print("hello, matt")  // where we import the Swift ?
    
    }
}

我们可以使用print或Swift.print，我只是想问，apple如何隐式导入Swift模块？很明显，UIKit，我们必须导入，如果可以隐式导入Swift模块，为什么苹果不隐式导入UIKit？

我的困惑是如何隐式导入 Swift 模块？

Answer 1

Swift 模块的隐式导入是一种硬编码到 Swift 编译器中的行为，专门用于 Swift 模块。