upgrading Heroes

I have a question if someone can give me an answer. It is been told that, Heroes and defense that are being upgraded will be effective in clan wars. So they will all be there for defense. How about in attack? Is an upgrading hero will be available in a clan wars attack?
Thanks

im wondering too. gonna upgrade my barbarian king later

Please elaborate more to further understand your judgement.

Upgrading heroes cannot be used for attack