Error: undefined method `each' for "1":String - ruby-on-rails

Question

I'm trying to associate a model Thing with another Thing on my things/new form. Each Thing has_many :things through a join table :related_things.
When I submit the form, I get this error:
NoMethodError in ThingsController#create
undefined method `each' for "1":String
Where did I go wrong with my code?
Thing model: I put asterisks around the line with the error message.
class Thing < ActiveRecord::Base
has_many :related_things
has_many :things, :through => :related_things
has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "30x30!" }, :default_url => "/images/:style/missing.png"
validates_attachment_content_type :avatar, :content_type => /\Aimage\/.*\Z/
def related_things
related_thing_ids = RelatedThing.
where("thing_a_id = ? OR thing_b_id = ?", self.id, self.id).
map { |r| [r.thing_a_id, r.thing_b_id] }.
flatten - [self.id]
Thing.where(id: related_thing_ids)
end
def related_thing_ids=(ids)
***ids.each do |id|***
record = RelatedThing.where(thing_a_id: self.id, thing_b_id: id).first
record ||= RelatedThing.where(thing_a_id: id, thing_b_id: self.id).first
record ||= RelatedThing.create!(thing_a_id: self.id, thing_b_id: id)
end
end
end
RelatedThing model:
class RelatedThing < ActiveRecord::Base
has_many :things
end
Things controller:
class ThingsController < ApplicationController
def show
#thing = Thing.find(params[:id])
#related_thing = RelatedThing.all
#thing.things.build
end
def new
#thing = Thing.new
#things = Thing.all
end
def create
#thing = Thing.new(thing_params)
if #thing.save
redirect_to #thing
else
render 'new'
end
end
private
def thing_params
params.require(:thing).permit(:name, :avatar, :related_thing_ids)
end
end
Things/new.html.erb:
<h1>Add Something!</h1>
<p>
<%= form_for #thing, :url => things_path, :html => { :multipart => true } do |f| %>
<%= f.text_field :name, :placeholder => "Name of the thing" %>
<br>
<%= f.label :related_things %>
<%= f.collection_select :related_thing_ids, Thing.all, :id, :name %>
<br>
<%= f.label :display_picture %>
<%= f.file_field :avatar %>
<br>
<%= f.submit "Submit", class: "btn btn-primary" %>
<% end %>
</p>
Schema.rb:
ActiveRecord::Schema.define(version: 20141016190146) do
create_table "related_things", force: true do |t|
t.integer "thing_a_id"
t.integer "thing_b_id"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "things", force: true do |t|
t.string "name"
t.datetime "created_at"
t.datetime "updated_at"
t.string "avatar_file_name"
t.string "avatar_content_type"
t.integer "avatar_file_size"
t.datetime "avatar_updated_at"
end
end
I'm using Rails 4.0.10.

Answer 1

Try Array(ids).each ..., which convert any object in an array and respond to :each
~ (main) > Array(nil)
=> []
~ (main) > Array([])
=> []
~ (main) > Array('')
=> [""]
~ (main) > Array(1)
=> [1]
See Kernel#Array