Class: ActiveRecord::Migration::CommandRecorder

Inherits:
Object
  • Object
show all
Includes:
StraightReversions, JoinTable
Defined in:
activerecord/lib/active_record/migration/command_recorder.rb

Overview

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

Defined Under Namespace

Modules: StraightReversions

Constant Summary collapse

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
]

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(delegate = nil) ⇒ CommandRecorder

Returns a new instance of CommandRecorder.


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

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) ⇒ Object (private)

Forwards any missing method call to the target.


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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 229

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

Instance Attribute Details

#commandsObject

Returns the value of attribute commands


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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 40

def commands
  @commands
end

#delegateObject

Returns the value of attribute delegate


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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 40

def delegate
  @delegate
end

#revertingObject

Returns the value of attribute reverting


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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 40

def reverting
  @reverting
end

Instance Method Details

#change_table(table_name, options = {}) {|delegate.update_table_definition(table_name, self)| ... } ⇒ Object

:nodoc:

Yields:

  • (delegate.update_table_definition(table_name, self))

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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 109

def change_table(table_name, options = {}) # :nodoc:
  yield delegate.update_table_definition(table_name, self)
end

#inverse_of(command, args, &block) ⇒ Object

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.


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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 84

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

#record(*command, &block) ⇒ Object

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

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

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# 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

#respond_to?(*args) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 95

def respond_to?(*args) # :nodoc:
  super || delegate.respond_to?(*args)
end

#revertObject

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])


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# 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