column
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- 7.1.3.2 (0)
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- What's this?
column(name, type, index: nil, **options)
public
Instantiates a new column for the table. See {connection.add_column}[rdoc-ref:ConnectionAdapters::SchemaStatements#add_column] for available options.
Additional options are:
This method returns self.
Examples
# Assuming +td+ is an instance of TableDefinition td.column(:granted, :boolean, index: true)
Short-hand examples
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}[rdoc-ref:ConnectionAdapters::SchemaStatements#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