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Migration Command Recorder ↑

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_exclusion_constraint

  • add_unique_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_enum

  • create_join_table

  • create_virtual_table

  • create_table

  • disable_extension

  • drop_enum (must supply a list of values)

  • drop_join_table

  • drop_virtual_table (must supply options)

  • 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_exclusion_constraint

  • remove_unique_constraint

  • remove_index

  • remove_reference

  • remove_timestamps

  • rename_column

  • rename_enum

  • rename_enum_value (must supply a :from and :to option)

  • rename_index

  • rename_table

  • enable_index

  • disable_index

Methods
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, :add_exclusion_constraint, :remove_exclusion_constraint, :add_unique_constraint, :remove_unique_constraint, :create_enum, :drop_enum, :rename_enum, :add_enum_value, :rename_enum_value, :create_schema, :drop_schema, :create_virtual_table, :drop_virtual_table, :enable_index, :disable_index ].freeze
 

Attributes

[RW] commands
[RW] delegate
[RW] reverting

Class Public methods

new(delegate = nil)

Source: show | on GitHub 

# File activerecord/lib/active_record/migration/command_recorder.rb, line 69
def initialize(delegate = nil)
  @commands = []
  @delegate = delegate
  @reverting = false
end

Instance Public methods

replay(migration)

Source: show | on GitHub 

# File activerecord/lib/active_record/migration/command_recorder.rb, line 114
def replay(migration)
  commands.each do |cmd, args, kwargs, block|
    migration.send(cmd, *args, **kwargs, &block)
  end
end

revert()

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.rename_table(:old, :new) }
# same effect as recorder.rename_table(:new, :old)

Source: show | on GitHub 

# File activerecord/lib/active_record/migration/command_recorder.rb, line 82
def revert
  @reverting = !@reverting
  previous = @commands
  @commands = []
  yield
ensure
  @commands = previous.concat(@commands.reverse)
  @reverting = !@reverting
end