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Class: ActiveRecord::Migration::CommandRecorder

Relationships & Source Files
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_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

Constant Summary

  • ReversibleAndIrreversibleMethods =
    # File 'activerecord/lib/active_record/migration/command_recorder.rb', line 33 
    [: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
]

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 44



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 231



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


  







Instance Attribute Details



  

    #commands   (rw)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 42



attr_accessor :commands, :delegate, :reverting


  








  

    #delegate   (rw)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 42



attr_accessor :commands, :delegate, :reverting


  








  

    #reverting   (rw)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 42



attr_accessor :commands, :delegate, :reverting


  







Instance Method Details



  

    #add_belongs_to  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 104



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 86



def inverse_of(command, args, &block)
  method = :"invert_#{command}"
  raise IrreversibleMigration, <<-MSG.strip_heredoc 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


  








  

    #invert_add_belongs_to  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 183



alias :invert_add_belongs_to :invert_add_reference


  








  

    #invert_add_foreign_key(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 201



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 160



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

  options_hash = options.slice(:name, :algorithm)
  options_hash[:column] = columns if !options_hash[:name]

  [:remove_index, [table, options_hash]]
end


  








  

    #invert_change_column_default(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 186



def invert_change_column_default(args)
  table, column, options = *args

  unless options && options.is_a?(Hash) && options.has_key?(:from) && options.has_key?(:to)
    raise ActiveRecord::IrreversibleMigration, "change_column_default is only reversible if given a :from and :to option."
  end

  [:change_column_default, [table, column, from: options[:to], to: options[:from]]]
end


  








  

    #invert_change_column_null(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 196



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 136



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 184



alias :invert_remove_belongs_to :invert_remove_reference


  








  

    #invert_remove_column(args)  
  



  

    
  





  
Raises:





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 147



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_foreign_key(args)  
  



  

    
  





  
Raises:





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 216



def invert_remove_foreign_key(args)
  from_table, to_table, remove_options = args
  raise ActiveRecord::IrreversibleMigration, "remove_foreign_key is only reversible if given a second table" if to_table.nil? || to_table.is_a?(Hash)

  reversed_args = [from_table, to_table]
  reversed_args << remove_options if remove_options

  [:add_foreign_key, reversed_args]
end


  








  

    #invert_remove_index(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 170



def invert_remove_index(args)
  table, options_or_column = *args
  if (options = options_or_column).is_a?(Hash)
    unless 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]]
  elsif (column = options_or_column).present?
    [:add_index, [table, column]]
  end
end


  








  

    #invert_rename_column(args)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 156



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 152



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 143



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 71



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 105



alias :remove_belongs_to :remove_reference


  








  

    #respond_to_missing?(method, _)  ⇒ Boolean 
  



  

    
  





  


  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 226



def respond_to_missing?(method, _)
  super || delegate.respond_to?(method)
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.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 57



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