Swift iOS应用程序从何处开始？ [英] Where does a Swift iOS application begin its life?

问题描述

如果我在Xcode中创建一个Objective-C iOS应用程序，则会生成一个名为 main.m 的文件。该文件的内容如下所示：

If I create an Objective-C iOS application in Xcode, a file named main.m is generated. The contents of the file look something like this:

#import <UIKit/UIKit.h>
#import "AppDelegate.h"

int main(int argc, char * argv[]) {
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

这是Objective-C iOS应用程序开始的地方它的生命。

And this is where an Objective-C iOS application begins its life.

重要的是，如果我想继承 UIApplication （无论出于何种原因），那么这里是我去告诉我的应用程序用于应用程序类的类。同样，如果由于某种原因我想为我的应用程序使用 AppDelegate 以外的类名，我会在这里更改这些信息。

Importantly, if I want to subclass UIApplication (for whatever reason), then here is where I go to tell my app which class to use for the application class. Likewise, if for some reason I want to use a class name other than AppDelegate for my app, I'd change that information here.

HOWEVER ，如果我在Xcode中创建Swift iOS应用程序，则不会生成此类文件（我已经能够找到）。我在哪里设置这些东西？

HOWEVER, if I create a Swift iOS application in Xcode, no such file is generated (that I've been able to find). Where do I set these things up at?

推荐答案

在Swift中你可以使用 @UIApplicationMain 属性，它将自动为您调用 UIApplicationMain（）函数。

In Swift you can use the @UIApplicationMain attribute on your app delegate class, and it will automatically call the UIApplicationMain() function for you.

@UIApplicationMain
class YourAppDelegate: UIResponder, UIApplicationDelegate { ...

还有另一种选择：

如果你不使用这个属性，请提供一个带有a的main.swift文件调用 UIApplicationMain 函数的 main 函数。例如，如果您的应用使用自定义子类 UIApplication 作为其主要类，请调用 UIApplicationMain 函数而不是使用此属性。

If you do not use this attribute, supply a main.swift file with a main function that calls the UIApplicationMain function. For example, if your app uses a custom subclass of UIApplication as its principal class, call the UIApplicationMain function instead of using this attribute.

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参考文献：

• Swift编程语言：属性


• 什么做@UIApplicationMain"是什么意思？

• The Swift Programming Language: Attributes
• What does "@UIApplicationMain" mean?

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