Has and Belongs to Many

habtm.md

has_and_belongs_to_many and :through do not go together. Your Entry has_and_belongs_to_many :tags:

class Entry < ActiveRecord::Base
  has_and_belongs_to_many :tags
end

class Tag < ActiveRecord::Base
  has_and_belongs_to_many :entries
end

create_table :entry do |t|
  t.string :content, null: false
end

create_table :tags do |t|
  t.string :name, null: false, uniqueness: true
end

create_table :entries_tags do |t|
  t.belongs_to :entry 
  t.belongs_to :tag
end