instance method `column`

Ruby on Rails 6.1.7.10

Since v2.2.3

Available in: v2.2.3 v2.3.18 v3.0.20 v3.1.12 v3.2.22.5 v4.0.13 v4.1.16 v4.2.9 v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

column(name, type, index: nil, **options)

Instantiates a new column for the table. See connection.add_column for available options.

Additional options are:

:index - Create an index for the column. Can be either true or an options hash.

This method returns self.

Examples

# Assuming +td+ is an instance of TableDefinition
td.column(:granted, :boolean, index: true)

Instead of calling #column directly, you can also work with the short-hand definitions for the default types. They use the type as the method name instead of as a parameter and allow for multiple columns to be defined in a single statement.

What can be written like this with the regular calls to column:

create_table :products do |t|
  t.column :shop_id,     :integer
  t.column :creator_id,  :integer
  t.column :item_number, :string
  t.column :name,        :string, default: "Untitled"
  t.column :value,       :string, default: "Untitled"
  t.column :created_at,  :datetime
  t.column :updated_at,  :datetime
end
add_index :products, :item_number

can also be written as follows using the short-hand:

create_table :products do |t|
  t.integer :shop_id, :creator_id
  t.string  :item_number, index: true
  t.string  :name, :value, default: "Untitled"
  t.timestamps null: false
end

There’s a short-hand method for each of the type values declared at the top. And then there’s TableDefinition#timestamps that’ll add created_at and updated_at as datetimes.

TableDefinition#references will add an appropriately-named _id column, plus a corresponding _type column if the :polymorphic option is supplied. If :polymorphic is a hash of options, these will be used when creating the _type column. The :index option will also create an index, similar to calling add_index. So what can be written like this:

create_table :taggings do |t|
  t.integer :tag_id, :tagger_id, :taggable_id
  t.string  :tagger_type
  t.string  :taggable_type, default: 'Photo'
end
add_index :taggings, :tag_id, name: 'index_taggings_on_tag_id'
add_index :taggings, [:tagger_id, :tagger_type]

Can also be written as follows using references:

create_table :taggings do |t|
  t.references :tag, index: { name: 'index_taggings_on_tag_id' }
  t.references :tagger, polymorphic: true
  t.references :taggable, polymorphic: { default: 'Photo' }, index: false
end

Parameters

name req
type req
index key = nil
options keyrest

Source

# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 405
      def column(name, type, index: nil, **options)
        name = name.to_s
        type = type.to_sym if type

        if @columns_hash[name]
          if @columns_hash[name].primary_key?
            raise ArgumentError, "you can't redefine the primary key column '#{name}'. To define a custom primary key, pass { id: false } to create_table."
          else
            raise ArgumentError, "you can't define an already defined column '#{name}'."
          end
        end

        @columns_hash[name] = new_column_definition(name, type, **options)

        if index
          index_options = index.is_a?(Hash) ? index : {}
          index(name, **index_options)
        end

        self
      end

Defined in activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb line 405 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::ConnectionAdapters::TableDefinition

Signature

Examples

Short-hand examples

Parameters