 class ActiveRecor8b7c:f320:99b9:690f:4595:cd17:293a:c069Migration8b7c:f320:99b9:690f:4595:cd17:293a:c069ommandRecorder 

Parent:
Object
Included modules:
ActiveRecor8b7c:f320:99b9:690f:4595:cd17:293a:c069Migration8b7c:f320:99b9:690f:4595:cd17:293a:c069ommandRecorder8b7c:f320:99b9:690f:4595:cd17:293a:c069StraightReversions
  ActiveRecor8b7c:f320:99b9:690f:4595:cd17:293a:c069Migration8b7c:f320:99b9:690f:4595:cd17:293a:c069ommandRecorder 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 
     Constants   ReversibleAndIrreversibleMethods 
    Attributes    commands[RW]     delegate[RW]     reverting[RW]      Public Class Methods    new(delegate = nil) Show source  
 # File activerecord/lib/active_record/migration/command_recorder.rb, line 42
def initialize(delegate = nil)
  @commands = []
  @delegate = delegate
  @reverting = false
end       Public Instance Methods    inverse_of(command, args, &block) Show source  
 # 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  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.     record(*command, &block) Show source  
 # File activerecord/lib/active_record/migration/command_recorder.rb, line 69
def record(*command, &block)
  if @reverting
    @commands << inverse_of(*command, &block)
  else
    @commands << (command << block)
  end
end  Record command. command should be a method name and arguments. For example: recorder.record(:method_name, [:arg1, :arg2])
     revert() { || ... } Show source  
 # File activerecord/lib/active_record/migration/command_recorder.rb, line 55
def revert
  @reverting = !@reverting
  previous = @commands
  @commands = []
  yield
ensure
  @commands = previous.concat(@commands.reverse)
  @reverting = !@reverting
end  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])
    

    
{'path': 'public/docs/rails~5.1/activerecord/migration/commandrecorder.html', 'source': 'DevDocs.IO'}