Call app delegate method from view controller

问题

I want to know if I can call an app delegate method from another ViewController.

When the app starts, the application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool i method is called. Can I call this method a second time from another view controller?

回答1:

Not sure why you want to do this. You probably shouldn't, but for the purpose of answering the question here it is:

// get a reference to the app delegate
let appDelegate: AppDelegate? = UIApplication.shared.delegate as? AppDelegate

// call didFinishLaunchWithOptions ... why?
appDelegate?.application(UIApplication.shared, didFinishLaunchingWithOptions: nil)

回答2:

In Swift 3.0, you can call as:

let appDelegate = UIApplication.shared.delegate as! AppDelegate
appDelegate.anyAppDelegateInstaceMethod()

回答3:

This method is called just once when app launches. You can't from ViewController. Instead make user defined method in AppDelegete. and call that method from ViewController. By getting object of AppDelegate.

AppDelegate *appDel = (AppDelegate *)[UIApplication sharedApplication].delegate;
[appDel <Your method>];

回答4:

Constructors:

Add a constructor in AppDelegate Class at the end of code

Swift 3.x

 class func shared() -> AppDelegate
{
    return UIApplication.shared.delegate as! AppDelegate
}

Swift 2.x

func appDelegate () -> AppDelegate
{
return UIApplication.sharedApplication().delegate as! AppDelegate
}

and add a var like this

var boolForFun = Bool()

How to use reference in your class?

Method

for swift 3x access functins or variables

AppDelegate.shared().boolForFun = true

for else

appDelegate().methodFoo()

Variable

appDelegate().foo

来源：https://stackoverflow.com/questions/30705214/call-app-delegate-method-from-view-controller

标签

ios

swift

appdelegate