CODEWITHSUNDEEP
c#objective-c.netxamarin.ios
Kostub Deshmukh
Kostub Deshmukh

Reputation: 2952

C#: A method parameter that implements a particular interface

Let's say I have a class called UIViewController.

public class UIViewController
{
    // ... methods
}

And I have an interface IDoFancyFlips

public interface IDoFancyFlips
{
   // ... methods
}

I have a classes that extend UIViewController and implement the interface as follows.

public class FancyViewController : UIViewController, IDoFancyFlips
{
   // ... methods
}

Now I want to write a method that takes a UIViewController as a parameter, but only ones that implement IDoFancyFlips.

public void FlipAndShow(??? controller) {
    // implementation
}

My question is what do I put in the ???. I couldn't seem to find any way to do this.

I can do this in Objective C as follows:

- (void) flipAndShow:(UIViewController<IDoFancyFlips>*) controller {
    // implementation
}

But I can't find the equivalent declaration in C#.

Upvotes: 2

Views: 77

Answers (2)

Tyree Jackson
Tyree Jackson

Reputation: 2608

You can use generics to accomplish this. Try the following:

public void FlipAndShow<TFancyFlippingController>
       (TFancyFlippingController fancyFlippingController) 
     where TFancyFlippingController : UIViewController, IDoFancyFlips
{
    // implementation
}

The where TFancyFlippingController : UIViewController, IDoFancyFlips constraint ensures that the argument specified for TFancyFlippingController must both inherit from UIViewController and implement the IDoFancyFlips interface.

Upvotes: 4

Rahul
Rahul

Reputation: 77896

Considering that all your specific view controller inherits from base UIViewController class 

public class FancyViewController : UIViewController, DoFancyFlips
{
    // ... methods
}

public class NormalViewController : UIViewController
{
    // ... methods
}

you can check at runtime whether the passed instance is of type DoFancyFlips and then do the processing further; like

    public static void FlipAndShow(UIViewController controller)
    {
        if (!(controller is DoFancyFlips))
            return;

        // implementation
    }

Upvotes: 0

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