Rails ActiveRecord: Find All Users Except Current User

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] : [])