ActiveRecord::Migration::CommandRecorder
records commands done during a migration and knows how to reverse those commands. The CommandRecorder
knows how to invert the following commands:
-
add_column
-
add_foreign_key
-
add_check_constraint
-
add_index
-
add_reference
-
add_timestamps
-
change_column_default (must supply a
:from
and:to
option) -
change_column_null
-
change_column_comment (must supply a
:from
and:to
option) -
change_table_comment (must supply a
:from
and:to
option) -
create_join_table
-
create_table
-
disable_extension
-
drop_join_table
-
drop_table (must supply a block)
-
enable_extension
-
remove_column (must supply a type)
-
remove_columns (must supply a
:type
option) -
remove_foreign_key (must supply a second table)
-
remove_check_constraint
-
remove_index
-
remove_reference
-
remove_timestamps
-
rename_column
-
rename_index
-
rename_table
- I
- N
- R
Constants
ReversibleAndIrreversibleMethods | = | [ :create_table, :create_join_table, :rename_table, :add_column, :remove_column, :rename_index, :rename_column, :add_index, :remove_index, :add_timestamps, :remove_timestamps, :change_column_default, :add_reference, :remove_reference, :transaction, :drop_join_table, :drop_table, :execute_block, :enable_extension, :disable_extension, :change_column, :execute, :remove_columns, :change_column_null, :add_foreign_key, :remove_foreign_key, :change_column_comment, :change_table_comment, :add_check_constraint, :remove_check_constraint ] |
Attributes
[RW] | commands | |
[RW] | delegate | |
[RW] | reverting |
Class Public methods
new(delegate = nil) Link
Instance Public methods
inverse_of(command, args, &block) Link
Returns the inverse of the given command. For example:
recorder.inverse_of(:rename_table, [:old, :new])
# => [:rename_table, [:new, :old]]
If the inverse of a command requires several commands, returns array of commands.
recorder.inverse_of(:remove_columns, [:some_table, :foo, :bar, type: :string])
# => [[:add_column, :some_table, :foo, :string], [:add_column, :some_table, :bar, :string]]
This method will raise an IrreversibleMigration
exception if it cannot invert the command
.
# File activerecord/lib/active_record/migration/command_recorder.rb, line 97 def inverse_of(command, args, &block) method = :"invert_#{command}" raise IrreversibleMigration, <<~MSG unless respond_to?(method, true) This migration uses #{command}, which is not automatically reversible. To make the migration reversible you can either: 1. Define #up and #down methods in place of the #change method. 2. Use the #reversible method to define reversible behavior. MSG send(method, args, &block) end
record(*command, &block) Link
Record command
. command
should be a method name and arguments. For example:
recorder.record(:method_name, [:arg1, :arg2])
replay(migration) Link
revert() Link
While executing the given block, the recorded will be in reverting mode. All commands recorded will end up being recorded reverted and in reverse order. For example:
recorder.revert{ recorder.record(:rename_table, [:old, :new]) }
# same effect as recorder.record(:rename_table, [:new, :old])