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Class: ActiveRecord::Migration::CommandRecorder

Relationships & Source Files
Namespace Children
Modules:
StraightReversions
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, StraightReversions
Inherits: Object
Defined in: activerecord/lib/active_record/migration/command_recorder.rb

Overview

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_index

  • add_timestamps

  • create_table

  • create_join_table

  • remove_timestamps

  • rename_column

  • rename_index

  • rename_table

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(delegate = nil) ⇒ CommandRecorder

[ GitHub ] 

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 21



def initialize(delegate = nil)
  @commands = []
  @delegate = delegate
  @reverting = false
end


  







Dynamic Method Handling

  

    This class handles dynamic methods through the method_missing method




  

    #method_missing(method, *args, &block)  
  



  

    

Forwards any missing method call to the target.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 188



def method_missing(method, *args, &block)
  if @delegate.respond_to?(method)
    @delegate.send(method, *args, &block)
  else
    super
  end
end


  







Instance Attribute Details



  

    #commands   (rw)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 19



attr_accessor :commands, :delegate, :reverting


  








  

    #delegate   (rw)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 19



attr_accessor :commands, :delegate, :reverting


  








  

    #reverting   (rw)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 19



attr_accessor :commands, :delegate, :reverting


  







Instance Method Details



  

    #add_belongs_to  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 87



alias :add_belongs_to :add_reference


  








  

    #inverse_of(command, args, &block)  
  



  

    

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 ::ActiveRecord::IrreversibleMigration exception if it cannot invert the command.


  





  
Raises:





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 63



def inverse_of(command, args, &block)
  method = :"invert_#{command}"
  raise IrreversibleMigration unless respond_to?(method, true)
  send(method, args, &block)
end


  








  

    #invert_add_belongs_to  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 164



alias :invert_add_belongs_to :invert_add_reference


  








  

    #invert_add_foreign_key(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 172



def invert_add_foreign_key(args)
  from_table, to_table, add_options = args
  add_options ||= {}

  if add_options[:name]
    options = { name: add_options[:name] }
  elsif add_options[:column]
    options = { column: add_options[:column] }
  else
    options = to_table
  end

  [:remove_foreign_key, [from_table, options]]
end


  








  

    #invert_add_index(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 143



def invert_add_index(args)
  table, columns, options = *args
  options ||= {}

  index_name = options[:name]
  options_hash = index_name ? { name: index_name } : { column: columns }

  [:remove_index, [table, options_hash]]
end


  








  

    #invert_change_column_null(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 167



def invert_change_column_null(args)
  args[2] = !args[2]
  [:change_column_null, args]
end


  








  

    #invert_drop_table(args, &block)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 119



def invert_drop_table(args, &block)
  if args.size == 1 && block == nil
    raise ActiveRecord::IrreversibleMigration, "To avoid mistakes, drop_table is only reversible if given options or a block (can be empty)."
  end
  super
end


  








  

    #invert_remove_belongs_to  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 165



alias :invert_remove_belongs_to :invert_remove_reference


  








  

    #invert_remove_column(args)  
  



  

    
  





  
Raises:





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 130



def invert_remove_column(args)
  raise ActiveRecord::IrreversibleMigration, "remove_column is only reversible if given a type." if args.size <= 2
  super
end


  








  

    #invert_remove_index(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 153



def invert_remove_index(args)
  table, options = *args

  unless options && options.is_a?(Hash) && options[:column]
    raise ActiveRecord::IrreversibleMigration, "remove_index is only reversible if given a :column option."
  end

  options = options.dup
  [:add_index, [table, options.delete(:column), options]]
end


  








  

    #invert_rename_column(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 139



def invert_rename_column(args)
  [:rename_column, [args.first] + args.last(2).reverse]
end


  








  

    #invert_rename_index(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 135



def invert_rename_index(args)
  [:rename_index, [args.first] + args.last(2).reverse]
end


  








  

    #invert_rename_table(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 126



def invert_rename_table(args)
  [:rename_table, args.reverse]
end


  








  

    #record(*command, &block)  
  



  

    

record command. command should be a method name and arguments. For example:



recorder.record(:method_name, [:arg1, :arg2])


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 48



def record(*command, &block)
  if @reverting
    @commands << inverse_of(*command, &block)
  else
    @commands << (command << block)
  end
end


  








  

    #remove_belongs_to  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 88



alias :remove_belongs_to :remove_reference


  








  

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


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 34



def revert
  @reverting = !@reverting
  previous = @commands
  @commands = []
  yield
ensure
  @commands = previous.concat(@commands.reverse)
  @reverting = !@reverting
end