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:
-
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
Constants
- ReversibleAndIrreversibleMethods
Attributes
Public Class Methods
# File lib/active_record/migration/command_recorder.rb, line 42 def initialize(delegate = nil) @commands = [] @delegate = delegate @reverting = false end
Public Instance Methods
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
.
# File 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
. 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 69 def record(*command, &block) if @reverting @commands << inverse_of(*command, &block) else @commands << (command << block) end end
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])
# File 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
Private Instance Methods
# File lib/active_record/migration/command_recorder.rb, line 203 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
# File lib/active_record/migration/command_recorder.rb, line 162 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
# File lib/active_record/migration/command_recorder.rb, line 188 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
# File lib/active_record/migration/command_recorder.rb, line 198 def invert_change_column_null(args) args[2] = !args[2] [:change_column_null, args] end
# File lib/active_record/migration/command_recorder.rb, line 138 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
# File lib/active_record/migration/command_recorder.rb, line 149 def invert_remove_column(args) raise ActiveRecord::IrreversibleMigration, "remove_column is only reversible if given a type." if args.size <= 2 super end
# File lib/active_record/migration/command_recorder.rb, line 218 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
# File lib/active_record/migration/command_recorder.rb, line 172 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
# File lib/active_record/migration/command_recorder.rb, line 158 def invert_rename_column(args) [:rename_column, [args.first] + args.last(2).reverse] end
# File lib/active_record/migration/command_recorder.rb, line 154 def invert_rename_index(args) [:rename_index, [args.first] + args.last(2).reverse] end
# File lib/active_record/migration/command_recorder.rb, line 145 def invert_rename_table(args) [:rename_table, args.reverse] end
Forwards any missing method call to the target.
# File 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