Question

How can I store/access global variables within a monotouch application? I am retrieving the GPS Location (using Monotouch.CoreLocation.CLLocationManager) during the FinishedLaunching method of the AppDelegate. How do I then access that information from a property on that appdelegate (from a view, for example)? Or is there another preferred method for global data?

UPDATE:
I just want to grab the location once, at startup, then have access to that location from all my views. Here’s my AppDelegate – I’d like to access the locationManager field from a view. I can certainly add a property to do so, but I guess my question is “How do I access that property from a view (or can I even, considering it’s a delegate)”?

// The name AppDelegate is referenced in the MainWindow.xib file.
public partial class AppDelegate : UIApplicationDelegate
{
    private CLLocationManager locationManager = new CLLocationManager();

    // This method is invoked when the application has loaded its UI and its ready to run
    public override bool FinishedLaunching (UIApplication app, NSDictionary options)
    {   
        locationManager.Delegate = new GpsLocationManagerDelegate();
        locationManager.StartUpdatingLocation();

        window.AddSubview (navController.View);
        window.MakeKeyAndVisible ();        
        return true;
    }

    // This method is required in iPhoneOS 3.0
    public override void OnActivated (UIApplication application)
    {
    }
}

Answer 1

Generally, most people will tell you to avoid global variables and instead pass what you need into the delegate. (I would agree with that sentiment).

However, you can use a singleton class, a service locator, or a static class with static fields/properties to get global variable-like behavior in C# (or any other Dotnet/Mono compatible language).

In your case, I presume you wrote the class GpsLocationManagerDelegate yourself. If so, you can change the constructor to take parameters for the necessary information (the view, a reference to the app delegate, and/or a reference to the location manager) and store it in your GpsLocationManagerDelegate instance. If you didn’t write GpsLocationManagerDelegate yourself and it’s not declared sealed, subclass it and create an appropriate constructor.

This example seems close to what you’re after: http://www.conceptdevelopment.net/iPhone/MapKit01/Main.cs.htm