monomac / Xamarin.Mac - derived NSTextField using NSTextViewDelegate

Question

In objective-C, I can make my subclass of NSTextField conform to the the NSTextViewDelegate protocol - like so:

@interface PasswordField : NSTextField <NSTextViewDelegate>

How can I translate this idiom to C# / monomac?

I have tried subclassing NSTextViewDelegate:

private class TextViewDelegate : NSTextViewDelegate
{}

And assigning that to the delegate property of my NSTextField subclass:

public class PasswordField : NSTextField
{
    public PasswordField(NSCoder coder) : base(coder)
    {
        this.Delegate = new TextViewDelegate();
    }
}

However, obviously this does not work since the Delegate property of NSTextField is (correctly) typed as NSTextFieldDelegate.

Error CS0029: Cannot implicitly convert type `PasswordFieldControl.PasswordField.TextViewDelegate' to `MonoMac.AppKit.NSTextFieldDelegate' (CS0029)

So how to make this work as it does in objective-C?

Answer 1

There are two ways to do this:

If you are fine with keeping the delegate separate, you can do this:

class TextViewDelegate : NSTextViewDelegate
{
    public override void TextDidChange (NSNotification notification)
    {
    }
}

public class PasswordField : NSTextField
{
    public PasswordField(NSCoder coder) : base(coder)
    {
        this.WeakDelegate = new TextViewDelegate();
    }
}

or, if you want to use the same PasswordField object:

public class PasswordField : NSTextField
{
    [Export("textDidChange:")]
    public void TextDidChange (NSNotification notification)
    {
    }

    public PasswordField(NSCoder coder) : base(coder)
    {
        this.WeakDelegate = this;
    }
}