在URL方案OpenURL之后从AppDelegate调用ViewController方法

Question

I am trying to call a function LoadWebpage in ViewController.m from AppDelegate.m.

I have enabled my app with a URL Scheme such that "urlscheme://?querystring" links in Safari open my app. I am capturing the url scheme in AppDelegate (I can tell by logging that this is working) and would like to fill a global variable with the querystring and then call my LoadWebPage method so that the view controller can use the global variable and open the requested website in a WebView control.

I am following this tutorial .

This is is AppDelegate.m:

- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation{
    NSLog(@"Calling Application Bundle ID: %@", sourceApplication);
    NSLog(@"URL scheme:%@", [url scheme]);
    NSLog(@"URL query:%@", [url query]);
    URLString = (NSString *)[url query]; //extern variable

    [self.ViewController loadWebpage];
    return YES;

}

And in ViewController.m:

- (void)LoadWebpage{

    NSString *strURL=URLString;  //more logic will be required to get the appropriate url from the query string.
    NSURL *url = [NSURL URLWithString:strURL];
    NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];
    [self.webview loadRequest:urlRequest];

}

But the line [self.ViewController loadWebpage]; has an error "Property 'ViewController' not found on object of type 'AppDelegate'".

I'm guessing I need to synthesize a reference to the open viewcontroller, but I can't find info on how to do this. Is this the best way to handle this?

Edit: Based on Yan's comment below, I tried to add

ViewController* mainController = (ViewController*)  self.window.rootViewController;
[mainController LoadWebpage];

Instead of [self.ViewController loadWebpage]; but it just ends debugging with lldb?

Answer 1

Rather than trying to have the AppDelegate trigger something off in your View Controller, I would suggest having the View Controller register to receive a notification when the app starts. You can then check the variable you're setting in AppDelegate and react accordingly.

For example:

YourViewController.m:

- (void)viewDidLoad {
    [super viewDidLoad];

    // This notification is sent the first time the app launches
    [[NSNotificationCenter defaultCenter] addObserver: self
                                             selector: @selector(applicationBecameActive:)
                                                 name: UIApplicationDidBecomeActiveNotification
                                               object: nil];

    // This notification is sent when the app resumes from the background
    [[NSNotificationCenter defaultCenter] addObserver: self
                                             selector: @selector(applicationEnteredForeground:)
                                                 name: UIApplicationWillEnterForegroundNotification
                                               object: nil];
}

Answer 2

For the ones, who have want it in Swift!

First, create NotificationCenter post method (In Swift 2.0 - NSNotification Center), where you want to send data:

    NotificationCenter.default.post(name: NSNotification.Name(rawValue: "NOTIFICATION_NAME"), object: nil)

    return true
}

In your ViewController class, where you want to receive the data, add the following in super.viewDidLoad():

NotificationCenter.default.addObserver(self,selector: #selector(self.YOUR_METHOD_NAME),
name: NSNotification.Name(rawValue: "NOTIFICATION_NAME"),
object: nil)

And the method you want to call:

func YOUR_METHOD_NAME(notification: NSNotification) {
    // Your method calling, or what you want to do with received data
}