AppDelegate.swift如何在Xcode 6.3中替换AppDelegate.h和AppDelegate.m [英] How does AppDelegate.swift replace AppDelegate.h and AppDelegate.m in Xcode 6.3

问题描述

根据 iOS开发人员库

应用程序委托是您编写自定义应用程序级代码的地方.与所有类一样，AppDelegate类在应用程序的两个源代码文件中定义:在接口文件AppDelegate.h和在实现文件AppDelegate.m中.

The app delegate is where you write your custom app-level code. Like all classes, the AppDelegate class is defined in two source code files in your app: in the interface file, AppDelegate.h, and in the implementation file, AppDelegate.m.

但是，在Xcode 6.3中，似乎只有AppDelegate.swift而没有.h和.m扩展名.我想了解.swift如何替换.h和.m扩展名.

However, in Xcode 6.3 it appears that there is only AppDelegate.swift and no longer the .h and .m extensions. I would like to understand how the .swift replaced both the .h and .m extensions.

推荐答案

简单的答案是AppDelegate.swift只是Objective-C AppDelegate.h和AppDelegate.m的翻译，因为Swift不需要单独的标头和实现，而是一个.swift文件.

The simple answer is that AppDelegate.swift is just the translation from Objective-C AppDelegate.h and AppDelegate.m, as Swift does not require separate headers and implementations, but rather a single .swift file.

但是，在内部，两者之间还有其他关键区别.

However, under the hood, there are other key differences between the two.

在Objective-C中，存在一个main.m文件，其唯一目的是实例化UIApplicationMain

In Objective-C, there exists a main.m file that's sole purpose is instantiating UIApplicationMain

在Swift中，位于AppDelegate.swift顶部的@UIApplicationMain注释标记取代了对Objective-C中main.m文件中存在的任何主要功能的需求.如果省略此标签，则可以使用main.swift文件使用指定的App Delegate实例化UIApplication.

In Swift, the @UIApplicationMain annotation tag found at the top of AppDelegate.swift replaces the need for any main function that existed in the main.m file in Objective-C. If this tag is omitted, you can use a main.swift file to instantiate your UIApplication using the specified App Delegate.

main.swift实现如下:

A main.swift implementation looks like this:

import UIKit

autoreleasepool {
    UIApplicationMain(Process.argc, Process.unsafeArgv, nil, NSStringFromClass(AppDelegate.self))
}

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