In an html page I try to: <%= render(MyPageView, "my_page1.html") %> Can’t render <%= render(MyPageView, "my_page1.html") %> because isn’t MyPageView is unavailable. But I’d already added alias MyApp.MyPageView to an appropriate controller. Why can’t it find it? How to fix it?

The template you are rendering and where you want to call render in, that belongs to a view, and in that view you need to alias.