Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
1.0k views
in Technique[技术] by (71.8m points)

objective c - Why not enforce strict singleton application delegate object to use in NIBs?

I just ran myself round in circles, all coming down to having instantiated an app delegate object in a secondary NIB that wasn't the NSMainNibFile. Amazing how having two app delegates kicking around means you have separate managedObjectContexts.

Here's a thought-- could I make my application delegate class a singleton? And safely instantiate it in more XIBs? What would that break?

Also, there are some mentions on stackoverflow that [[UIApplication sharedApplication] delegate] is a "singleton" but it doesn't appear that UIApplicationDelegate protocol guarantees that, nor is the superclass UIResponder a singleton, either. So could I shoot myself in the foot in this regard on iOS as well?

[edit] Looks like you could nil out the delegateClassName in UIApplicationMain for iOS and have the main NIB load the delegate object, so you could create the App Delegate object pattern seen on OSX, if using a main NIB.

[edit2] Screenshot of what MainMenu.xib looks like for a new non-document application. The project gets created with this object, app delegate class gets created with a window property. The issue is getting that nice handy object in other NIBs, and that object being the same as [NSApp delegate] enter image description here

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

Just do this in your existing App Delegate (There will only be one!)

// In the header file    
+ (AppDelegate*) sharedInstance;


// In the body
+ (AppDelegate*) sharedInstance {

    return (AppDelegate*) [[UIApplication sharedApplication] delegate];

}

Then anywhere you want to refer to your App Delegate, you can simply use [AppDelegate sharedInstance] followed by the property or instance method you want to call.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...