Icon image sizes

In Tutorial 2, we add icon files to the checklist app to be picked in IconPickerViewController. Looked at the icon sizes, the 2x png files are 72px and the 3x png files are 108px. Neither of these two matches the recommended icon sizes. Did I miss something here?

What recommended icon sizes are you referring to? From the app icons? Those are unrelated to the sizes of other icons that you add to your app.

Understand. Looks like there is no recommended image size for app internal icons and other images. Right?

It depends on where the icons are to be used.

There are guidelines for navigation bar icons and tab bar icons (see the Human Interface Guidelines document on developer.apple.com).

But for your own icons you can do whatever you want.

Many thanks, Matthijs!