group_by in rails by 2 or more attributes

问题

I have a @bunch of models returned as an array

each model has the attributes - commentable_id and commentable_type (polymorphic association)

I want to group the models by commentable, but if I do

@bunch.group_by(&:commentable)

it also fetches the commentable from the database, which is not needed.

I can do @bunch.group_by(&:commentable_id) but this will cause some confusions since there can be several types of commentable models

Is there a way to group_by commentable_id AND commentable_type?

回答1:

Why not do:

@bunch.group_by{|e| [e.commentable_id, e.commentable_type]}

来源：https://stackoverflow.com/questions/14660644/group-by-in-rails-by-2-or-more-attributes