问题
After installing Xcode 8 beta 6, I'm getting a warning saying:
Instance method 'application(_:didFinishLaunchingWithOptions:)' nearly matches optional requirement 'application(_:didFinishLaunchingWithOptions:)' of protocol 'UIApplicationDelegate'
in my App Delegate.
There are 2 suggested fixits to silence the warning:
- Mark the method as private
- Add @nonobjc to the method
Doing either silences the warning. But why does this need to be done?
回答1:
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 and 11 SDKs (Xcode 8 and 9)
This warning is due to the fact that the didFinishLaunchingWithOptions:
parameter of the application(_:didFinishLaunchingWithOptions:) delegate method is now bridged to Swift as a [UIApplicationLaunchOptionsKey: Any]?
, rather than an [NSObject : AnyObject]?
.
Therefore you'll need to update your implementation to reflect this change:
func application(
_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?
) -> Bool {
// ...
}
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.
回答2:
the first parameter passed into the function no longer has an external name. This is really just a minor detail since you don’t call this method directly, and it’s a quick fix to make the compiler happy. You can either manually edit that first parameter name to _, or just let Xcode handle this for you.
func application(_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions: [NSObject : AnyObject]?) -> Bool
or the New Syntax
func application(_ application:UIApplication,
didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey : Any]? = nil) -> Bool // or remove = nil and try
you can get the latest Documentation from apple and sample link in here
来源:https://stackoverflow.com/questions/38972440/application-didfinishlaunchingwithoptions-nearly-matches-optional-requireme