Ruby/Rails. Passing variable into parameters

I have a lot pages in my app. And for every page I need to create a new variable and describe method. And if I will need to change something, I will have to change on every page. So the idea is to create universal method in application_controller.rb.

For example, I have a lot of categories in my Posts and to target some category for page I did: @posts_for_interesting = Post.where(interesting: true), other category, for example: @posts_for_photos = Post.where(photos: true).

And the application_controller.rb, have to look something like that:

def posts_for_all_pages(category)
  @posts = Posts.where(category: true)
end

And, for example, photos_controller.rb must look like that:

posts_for_all_pages(photos)

And how can I pass this photos to Post.where(category: true)?