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_index

  • add_timestamps

  • create_table

  • create_join_table

  • remove_timestamps

  • rename_column

  • rename_index

  • rename_table

Defined Under Namespace

Modules: StraightReversions

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 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) ⇒ Object (private)

Forwards any missing method call to the target.



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# File 'activerecord/lib/active_record/migration/command_recorder.rb', line 160

def method_missing(method, *args, &block)
  @delegate.send(method, *args, &block)
rescue NoMethodError => e
  raise e, e.message.sub(/ for #<.*$/, " via proxy for #{@delegate}")
end

Instance Attribute Details

#commands ⇒ Object

Returns the value of attribute commands



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

def commands
  @commands
end

#delegate ⇒ Object

Returns the value of attribute delegate



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

def delegate
  @delegate
end

#reverting ⇒ Object

Returns the value of attribute reverting



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

def reverting
  @reverting
end

Instance Method Details

#change_table(table_name, options = {}) {|ConnectionAdapters::Table.new(table_name, self)| ... } ⇒ Object

Yields:



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

def change_table(table_name, options = {})
  yield ConnectionAdapters::Table.new(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.

Raises:



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# 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

#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 48

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 69

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

#revert ⇒ Object

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 34

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