Question

I have following output:

> group.items
=> [<Item id: 1, user_id: 7, group_id: 1>,<Item id: 2, user_id: 7, group_id: 1>,
    <Item id: 1, user_id: 2, group_id: 1>,<Item id: 2, user_id: 2, group_id: 1>,<Item id: 3, user_id: 2, group_id: 1>,
    <Item id: 4, user_id: 5, group_id: 1>]

How to delete all duplications and just leave one user2 item.

Goal

> group.items
=> [<Item id: 1, user_id: 7, group_id: 1>,
    <Item id: 1, user_id: 2, group_id: 1>,
    <Item id: 4, user_id: 5, group_id: 1>]

Answer 1

EDIT

I think, I first misunderstood your question. You want only one item per user – right?

I assume, you defined in the users model, that a user has many items, then the following should work:

old_items = group.items
group.items.delete_all
old_items.users.each do |user|
  group << user.items.first
end
group.save

Otherwise, if you just want a unique list, the following would be enough:

group.items = group.items.uniq