NoMethodError: undefined method `user' for has_many :through Association - ruby-on-rails

Question

I've attempted to create a has_many :through Association in my rails application, however I get an error when I do the following in the rails console.
2.0.0-p481 :001 > #group = Group.first
Group Load (0.2ms) SELECT "groups".* FROM "groups" ORDER BY "groups"."id" ASC LIMIT 1
=> #<Group id: 1, name: "First Group", description: "Woo", created_at: "2015-02-06 22:19:47", updated_at: "2015-02-06 22:19:47">
2.0.0-p481 :002 > #group.user
NoMethodError: undefined method `user' for #<Group:0x00000004d53eb0>
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/activemodel-4.0.2/lib/active_model/attribute_methods.rb:439:in `method_missing'
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/activerecord-4.0.2/lib/active_record/attribute_methods.rb:155:in `method_missing'
from (irb):2
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/railties-4.0.2/lib/rails/commands/console.rb:90:in `start'
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/railties-4.0.2/lib/rails/commands/console.rb:9:in `start'
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/railties-4.0.2/lib/rails/commands.rb:62:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
My Models:
User:
class User < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
before_create :do_mailchimp
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :memberships
has_many :groups, through: :memberships
def do_mailchimp
gb = Gibbon::API.new("API")
gb.lists.subscribe({:id => 'ID',
:email => {:email => self.email },:double_optin => false})
end
end
Group:
class Group < ActiveRecord::Base
has_many :memberships
has_many :users, through: :memberships
end
Membership:
class Membership < ActiveRecord::Base
belongs_to :user
belongs_to :group
end
My Migrations:
DeviseCreateUsers:
class DeviseCreateUsers < ActiveRecord::Migration
def change
create_table(:users) do |t|
## Database authenticatable
t.string :email, null: false, default: ""
t.string :encrypted_password, null: false, default: ""
## Recoverable
t.string :reset_password_token
t.datetime :reset_password_sent_at
## Rememberable
t.datetime :remember_created_at
## Trackable
t.integer :sign_in_count, default: 0, null: false
t.datetime :current_sign_in_at
t.datetime :last_sign_in_at
t.string :current_sign_in_ip
t.string :last_sign_in_ip
## Confirmable
# t.string :confirmation_token
# t.datetime :confirmed_at
# t.datetime :confirmation_sent_at
# t.string :unconfirmed_email # Only if using reconfirmable
## Lockable
# t.integer :failed_attempts, default: 0, null: false # Only if lock strategy is :failed_attempts
# t.string :unlock_token # Only if unlock strategy is :email or :both
# t.datetime :locked_at
t.timestamps
end
add_index :users, :email, unique: true
add_index :users, :reset_password_token, unique: true
# add_index :users, :confirmation_token, unique: true
# add_index :users, :unlock_token, unique: true
end
end
CreateGroups:
class CreateGroups < ActiveRecord::Migration
def change
create_table :groups do |t|
t.string :name
t.string :description
t.timestamps
end
end
end
CreateMemberships:
class CreateMemberships < ActiveRecord::Migration
def change
create_table :memberships do |t|
t.timestamps
end
end
end
AddUserAndGroupIdToMemberships:
class AddUserAndGroupIdToMemberships < ActiveRecord::Migration
def change
add_column :memberships, :user_id, :integer
add_index :memberships, :user_id
add_column :memberships, :group_id, :integer
add_index :memberships, :group_id
end
end
My Schema:
ActiveRecord::Schema.define(version: 20150206225251) do
create_table "groups", force: true do |t|
t.string "name"
t.string "description"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "memberships", force: true do |t|
t.datetime "created_at"
t.datetime "updated_at"
t.integer "user_id"
t.integer "group_id"
end
add_index "memberships", ["group_id"], name: "index_memberships_on_group_id"
add_index "memberships", ["user_id"], name: "index_memberships_on_user_id"
create_table "users", force: true do |t|
t.string "email", default: "", null: false
t.string "encrypted_password", default: "", null: false
t.string "reset_password_token"
t.datetime "reset_password_sent_at"
t.datetime "remember_created_at"
t.integer "sign_in_count", default: 0, null: false
t.datetime "current_sign_in_at"
t.datetime "last_sign_in_at"
t.string "current_sign_in_ip"
t.string "last_sign_in_ip"
t.datetime "created_at"
t.datetime "updated_at"
end
add_index "users", ["email"], name: "index_users_on_email", unique: true
add_index "users", ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
end
Thank you for your time hope you can help.

Answer 1

You defined that a Group has_many :users. Therefore a group does not have an user method, but an users method:
#group = Group.first
#group.users #=> returns an array with all users in the first group
#group.users.first #=> returns the first user in the first group