application（_：didFinishLaunchingWithOptions :)'几乎匹配可选要求 [英] application(_:didFinishLaunchingWithOptions:)' nearly matches optional requirement

问题描述

安装Xcode 8 beta 6后，我收到一条警告说：

After installing Xcode 8 beta 6, I'm getting a warning saying:

实例方法'应用程序（_：didFinishLaunchingWithOptions :) '几乎匹配我的应用程序代表中协议'UIApplicationDelegate'

Instance method 'application(_:didFinishLaunchingWithOptions:)' nearly matches optional requirement 'application(_:didFinishLaunchingWithOptions:)' of protocol 'UIApplicationDelegate'

的可选要求'application（_：didFinishLaunchingWithOptions :)'。

in my App Delegate.

有2个建议的修正可以使警告静音：

There are 2 suggested fixits to silence the warning:

1. 将方法标记为私有


2. 将@nonobjc添加到方法

执行任何操作都会使警告静音。但为什么需要这样做？

Doing either silences the warning. But why does this need to be done?

推荐答案

iOS 12 SDK更新

在iOS 12 SDK（随Xcode 10提供）中， UIApplicationLaunchOptionsKey 现已重命名为嵌套类型 UIApplication.LaunchOptionsKey ，所以你需要：

iOS 12 SDK Update

In the iOS 12 SDK (that ships with Xcode 10), UIApplicationLaunchOptionsKey has now been renamed to the nested type UIApplication.LaunchOptionsKey, so you'll want:

func application(
  _ application: UIApplication,
  didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool {
    // ...
}

---

iOS 10和11 SDK（Xcode 8和9）

此警告是由于 didFinishLaunchingWithOptions： 申请的参数（_ ：didFinishLaunchingWithOptions：） 委托方法现在桥接到Swift作为 [UIApplicationLaunchOptionsKey：Any]？，而不是 [NSObject：AnyObject]？。

因此，您需要更新实施以反映此更改：

Therefore you'll need to update your implementation to reflect this change:

func application(
  _ application: UIApplication,
  didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?
) -> Bool {
    // ...
}

注意Xcode都没有建议的修复程序实际上会修复问题，它们只会隐藏你从Objective-C中实现的应用程序（_：didFinishLaunchingWithOptions：） - 这意味着它实际上永远不会被调用。

Note that neither of Xcode's suggested fixes will actually fix the problem, they'll only conceal your implementation of application(_:didFinishLaunchingWithOptions:) from Objective-C – meaning that it'll never actually get called.

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