Added impl Default for Callback

[jfbilodeau]

Greetings,

I've added impl Default for Callback to make it easier to provide optional callback from component properties.

[jstarry]

Thanks @jfbilodeau!

We actually intentionally don't implement Default for Callback because it could cause unexpected behavior (devs might not realize they forgot to pass an optional callback to a component for example). I think the issue you are having will be resolved with the new Properties 2.0 proposal here: #928 It will make optional callbacks more explicit.

Feel free to weigh in!

[jfbilodeau]

Agreed. Props 2.0 is a much nicer solution. Thanks!