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_index
-
add_reference
-
add_timestamps
-
change_column
-
change_column_default (must supply a :from and :to option)
-
change_column_null
-
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 specify at least one column name or more)
-
remove_foreign_key (must supply a second table)
-
remove_index
-
remove_reference
-
remove_timestamps
-
rename_column
-
rename_index
-
rename_table
- I
- N
- R
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 ] |
[RW] | commands | |
[RW] | delegate | |
[RW] | reverting |
Returns the inverse of the given command. For example:
recorder.inverse_of(:rename_table, [:old, :new])
# => [:rename_table, [:new, :old]]
This method will raise an IrreversibleMigration
exception if
it cannot invert the command
.
# File activerecord/lib/active_record/migration/command_recorder.rb, line 84 def inverse_of(command, args, &block) method = :"invert_#{command}" raise IrreversibleMigration, " 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. ".strip_heredoc unless respond_to?(method, true) send(method, args, &block) end
Record command
. command
should be a method name
and arguments. For example:
recorder.record(:method_name, [:arg1, :arg2])
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])