Rails ActiveRecord: Find All Users Except Current User - ruby-on-rails

Question

I feel this should be very simple but my brain is short-circuiting on it. If I have an object representing the current user, and want to query for all users except the current user, how can I do this, taking into account that the current user can sometimes be nil?
This is what I am doing right now:
def index
#users = User.all
#users.delete current_user
end
What I don't like is that I am doing post-processing on the query result. Besides feeling a little wrong, I don't think this will work nicely if I convert the query over to be run with will_paginate. Any suggestions for how to do this with a query? Thanks.

Answer 1

It is possible to do the following in Rails 4 and up:
User.where.not(id: id)
You can wrap it in a nice scope.
scope :all_except, ->(user) { where.not(id: user) }
#users = User.all_except(current_user)
Or use a class method if you prefer:
def self.all_except(user)
where.not(id: user)
end
Both methods will return an AR relation object. This means you can chain method calls:
#users = User.all_except(current_user).paginate
You can exclude any number of users because where() also accepts an array.
#users = User.all_except([1,2,3])
For example:
#users = User.all_except(User.unverified)
And even through other associations:
class Post < ActiveRecord::Base
has_many :comments
has_many :commenters, -> { uniq }, through: :comments
end
#commenters = #post.commenters.all_except(#post.author)
See where.not() in the API Docs.

Answer 2

#users = (current_user.blank? ? User.all : User.find(:all, :conditions => ["id != ?", current_user.id]))

Answer 3

You can also create named_scope, e.g. in your model:
named_scope :without_user, lambda{|user| user ? {:conditions => ["id != ?", user.id]} : {} }
and in controller:
def index
#users = User.without_user(current_user).paginate
end
This scope will return all users when called with nil and all users except given in param in other case. The advantage of this solution is that you are free to chain this call with other named scopes or will_paginate paginate method.

Answer 4

Here is a shorter version:
User.all :conditions => (current_user ? ["id != ?", current_user.id] : [])

Answer 5

One note on GhandaL's answer - at least in Rails 3, it's worth modifying to
scope :without_user, lambda{|user| user ? {:conditions => ["users.id != ?", user.id]} : {} }
(the primary change here is from 'id != ...' to 'users.id !=...'; also scope instead of named_scope for Rails 3)
The original version works fine when simply scoping the Users table. When applying the scope to an association (e.g. team.members.without_user(current_user).... ), this change was required to clarify which table we're using for the id comparison. I saw a SQL error (using SQLite) without it.
Apologies for the separate answer...i don't yet have the reputation to comment directly on GhandaL's answer.

Answer 6

Very easy solution I used
#users = User.all.where("id != ?", current_user.id)

Answer 7

User.all.where("id NOT IN(?)", current_user.id) will through exception
undefined method where for #<Array:0x0000000aef08f8>
User.where("id NOT IN (?)", current_user.id)

Answer 8

Another easy way you could do it:
#users = User.all.where("id NOT IN(?)", current_user.id)

Answer 9

an array would be more helpful
arrayID[0]=1
arrayID[1]=3
User.where.not(id: arrayID)

Answer 10

User.where(:id.ne=> current_user.id)

Answer 11

ActiveRecord::QueryMethods#excluding (Rails 7+)
Starting from Rails 7, there is a new method ActiveRecord::QueryMethods#excluding.
A quote right from the official Rails docs:
excluding(*records)
Excludes the specified record (or collection of records) from the resulting relation. For example:
Post.excluding(post)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" != 1
Post.excluding(post_one, post_two)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" NOT IN (1, 2)
This can also be called on associations. As with the above example, either a single record of collection thereof may be specified:
post = Post.find(1)
comment = Comment.find(2)
post.comments.excluding(comment)
# SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = 1 AND "comments"."id" != 2
This is short-hand for .where.not(id: post.id) and .where.not(id: [post_one.id, post_two.id]).
An ArgumentError will be raised if either no records are specified, or if any of the records in the collection (if a collection is passed in) are not instances of the same model that the relation is scoping.
Also aliased as: without
Sources:
Official docs - ActiveRecord::QueryMethods#excluding
PR - Add #excluding to ActiveRecord::Relation to exclude a record (or collection of records) from the resulting relation.
What's Cooking in Rails 7?

Answer 12

What you are doing is deleting the current_user from the #users Array. This won't work since there isn't a delete method for arrays. What you probably want to do is this
def index
#users = User.all
#users - [current_user]
end
This will return a copy of the #users array, but with the current_user object removed (it it was contained in the array in the first place.
Note: This may not work if array subtraction is based on exact matches of objects and not the content. But it worked with strings when I tried it. Remember to enclose current_user in [] to force it into an Array.