This strange title is all that i think out.
I have to objects: @user (instance of User model) and @chat (instance of Chat model).
And i need to get record from table chats_users (relation has name chatusers) by these having objects, not by one of them and writing something like this: @user.chatusers.where(chat_id: @chat.id) or @chat.chatusers.where(user_id: @user.id).
What i looking foor must looking like this:
@user.double_relation(@chat, target: chatusers)