class ActiveRecord::Migration::CommandRecorder

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:

Attributes

commands[RW]
delegate[RW]

Public Class Methods

new(delegate = nil) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 18
def initialize(delegate = nil)
  @commands = []
  @delegate = delegate
end

Public Instance Methods

inverse() click to toggle source

Returns a list that represents commands that are the inverse of the commands stored in commands. For example:

recorder.record(:rename_table, [:old, :new])
recorder.inverse # => [:rename_table, [:new, :old]]

This method will raise an IrreversibleMigration exception if it cannot invert the commands.

# File lib/active_record/migration/command_recorder.rb, line 39
def inverse
  @commands.reverse.map { |name, args|
    method = :"invert_#{name}"
    raise IrreversibleMigration unless respond_to?(method, true)
    send(method, args)
  }
end
record(*command) click to toggle source

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

recorder.record(:method_name, [:arg1, :arg2])
# File lib/active_record/migration/command_recorder.rb, line 27
def record(*command)
  @commands << command
end

Private Instance Methods

invert_add_column(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 69
def invert_add_column(args)
  [:remove_column, args.first(2)]
end
invert_add_index(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 81
def invert_add_index(args)
  table, columns, options = *args
  index_name = options.try(:[], :name)
  options_hash =  index_name ? {:name => index_name} : {:column => columns}
  [:remove_index, [table, options_hash]]
end
invert_add_timestamps(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 92
def invert_add_timestamps(args)
  [:remove_timestamps, args]
end
invert_create_table(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 61
def invert_create_table(args)
  [:drop_table, [args.first]]
end
invert_remove_timestamps(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 88
def invert_remove_timestamps(args)
  [:add_timestamps, args]
end
invert_rename_column(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 77
def invert_rename_column(args)
  [:rename_column, [args.first] + args.last(2).reverse]
end
invert_rename_index(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 73
def invert_rename_index(args)
  [:rename_index, [args.first] + args.last(2).reverse]
end
invert_rename_table(args) click to toggle source
# File lib/active_record/migration/command_recorder.rb, line 65
def invert_rename_table(args)
  [:rename_table, args.reverse]
end
method_missing(method, *args, &block) click to toggle source

Forwards any missing method call to the target.

# File lib/active_record/migration/command_recorder.rb, line 97
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