How to handle array from collection_select rails

Question

I have a form that uses collection_select to be able to select multiple groups. But when I try to create a new record it fails in my notifications_controller.rb. The parameters are being passed correctly I think it might have to do with collection_select being passed as an array. I just can't for the life of me figure out how to handle it in the controller.

 undefined method `users' for #<Array:0x007fbb0e891b58>

What is being passed in the parameters:

 "group"=>{"group_id"=>["1", "2"]},

schema.rb

create_table "notifications", force: :cascade do |t|
 t.string "title"
 t.string "first_name"


 end

create_table "notifications_users", id: false, force: :cascade do |t|
 t.bigint "user_id", null: false
 t.bigint "notification_id", null: false
 end

create_table "users", force: :cascade do |t|
 t.string "first_name"
 t.string "last_name"
 t.string "user_type"
 t.string "username"


end

new.html.erb

   <%= f.label :To %>
       <%= collection_select(:group, :group_id, Group.all,:id,:name, 
        {include_hidden: false}, {:multiple => true})%>

notifications_controller.rb

def create

@notification = Notification.new(notification_params)


if @notification.save
  @group = Group.find(params[:group][:group_id])

  #raise @group.inspect

  @users = @group.users <--this is where it fails   
  @users.each do |user|
  @notification.users << user
end .....

Answer 1

Can you try:

def create

  @notification = Notification.new(notification_params)

  if @notification.save
    @group = Group.where(id: params[:group][:group_id])

    @group.each do |group|
      @users = group.users <--this is where it fails   
      @users.each do |user|
      @notification.users << user
    end
  end
end

As you're selecting multiple groups and searching the group, you'll be getting an Array of the Groups. Instead when using the where as above, you'll get a ActiveRecordRelation

You've to loop through this result and use the users association with each record.

Note : The associations don't work with Active Record Relations or Arrays.

Hope this helps. Let me know if this works for you.