Module: SchemaPlus::ForeignKeys::ActiveRecord::ConnectionAdapters::TableDefinition

Defined in:
lib/schema_plus/foreign_keys/active_record/connection_adapters/table_definition.rb

Overview

SchemaPlus::ForeignKeys adds several methods to TableDefinition, allowing indexes and foreign key constraints to be defined within a create_table block of a migration, allowing for better encapsulation and more DRY definitions.

For example, without SchemaPlus::ForeignKeys you might define a table like this:

create_table :widgets do |t|
   t.string :name
end
add_index :widgets, :name

But with SchemaPlus::ForeignKeys, the index can be defined within the create_table block, so you don’t need to repeat the table name:

create_table :widgets do |t|
   t.string :name
   t.index :name
end

Even more DRY, you can define the index as part of the column definition, via:

create_table :widgets do |t|
   t.string :name, index: true
end

For details about the :index option (including unique and multi-column indexes), see the documentation for Migration::ClassMethods#add_column

SchemaPlus::ForeignKeys also supports creation of foreign key constraints analogously, using Migration::ClassMethods#add_foreign_key or TableDefinition#foreign_key or as part of the column definition, for example:

create_table :posts do |t|  # not DRY
   t.references :author
end
add_foreign_key :posts, :author_id, references: :authors

create_table :posts do |t|  # DRYer
   t.references :author
   t.foreign_key :author_id, references: :authors
end

create_table :posts do |t|  # Dryest
   t.references :author, foreign_key: true
end

NOTE: In the standard configuration, SchemaPlus::ForeignKeys automatically creates foreign key constraints for columns whose names end in _id. So the above examples are redundant, unless automatic creation was disabled at initialization in the global Config.

SchemaPlus::ForeignKeys likewise by default automatically creates foreign key constraints for columns defined via t.references. However, SchemaPlus::ForeignKeys does not create foreign key constraints if the :polymorphic option is true

Finally, the configuration for foreign keys can be overriden on a per-table basis by passing Config options to Migration::ClassMethods#create_table, such as

create_table :students, foreign_keys: {auto_create: false} do
   t.references :student
end

Instance Attribute Summary collapse

Instance Attribute Details

#schema_plus_foreign_keys_config ⇒ Object

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# File 'lib/schema_plus/foreign_keys/active_record/connection_adapters/table_definition.rb', line 70

def schema_plus_foreign_keys_config
  @schema_plus_foreign_keys_config
end