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_check_constraint
-
add_index
-
add_reference
-
add_timestamps
-
change_column
-
change_column_default (must supply a :from and :to option)
-
change_column_null
-
change_column_comment (must supply a :from and :to option)
-
change_table_comment (must supply a :from and :to option)
-
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_check_constraint
-
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 51 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]]
If the inverse of a command requires several commands, returns array of commands.
recorder.inverse_of(:remove_columns, [:some_table, :foo, :bar, type: :string]) # => [[:add_column, :some_table, :foo, :string], [:add_column, :some_table, :bar, :string]]
This method will raise an IrreversibleMigration
exception if it cannot invert the command
.
# File lib/active_record/migration/command_recorder.rb, line 98 def inverse_of(command, args, &block) method = :"invert_#{command}" raise IrreversibleMigration, <<~MSG 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 78 def record(*command, &block) if @reverting @commands << inverse_of(*command, &block) else @commands << (command << block) end end
# File lib/active_record/migration/command_recorder.rb, line 124 def replay(migration) commands.each do |cmd, args, block| migration.send(cmd, *args, &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 64 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 252 def invert_change_column_comment(args) table, column, options = args unless options.is_a?(Hash) && options.has_key?(:from) && options.has_key?(:to) raise ActiveRecord::IrreversibleMigration, "change_column_comment is only reversible if given a :from and :to option." end [:change_column_comment, [table, column, from: options[:to], to: options[:from]]] end
# File lib/active_record/migration/command_recorder.rb, line 223 def invert_change_column_default(args) table, column, options = args unless 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 233 def invert_change_column_null(args) args[2] = !args[2] [:change_column_null, args] end
# File lib/active_record/migration/command_recorder.rb, line 262 def invert_change_table_comment(args) table, options = args unless options.is_a?(Hash) && options.has_key?(:from) && options.has_key?(:to) raise ActiveRecord::IrreversibleMigration, "change_table_comment is only reversible if given a :from and :to option." end [:change_table_comment, [table, from: options[:to], to: options[:from]]] end
# File lib/active_record/migration/command_recorder.rb, line 168 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 272 def invert_remove_check_constraint(args) raise ActiveRecord::IrreversibleMigration, "remove_check_constraint is only reversible if given an expression." if args.size < 2 super end
# File lib/active_record/migration/command_recorder.rb, line 179 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 184 def invert_remove_columns(args) unless args[-1].is_a?(Hash) && args[-1].has_key?(:type) raise ActiveRecord::IrreversibleMigration, "remove_columns is only reversible if given a type." end [:add_columns, args] end
# File lib/active_record/migration/command_recorder.rb, line 238 def invert_remove_foreign_key(args) options = args.extract_options! from_table, to_table = args to_table ||= options.delete(:to_table) raise ActiveRecord::IrreversibleMigration, "remove_foreign_key is only reversible if given a second table" if to_table.nil? reversed_args = [from_table, to_table] reversed_args << options unless options.empty? [:add_foreign_key, reversed_args] end
# File lib/active_record/migration/command_recorder.rb, line 202 def invert_remove_index(args) options = args.extract_options! table, columns = args columns ||= options.delete(:column) unless columns raise ActiveRecord::IrreversibleMigration, "remove_index is only reversible if given a :column option." end options.delete(:if_exists) args = [table, columns] args << options unless options.empty? [:add_index, args] end
# File lib/active_record/migration/command_recorder.rb, line 197 def invert_rename_column(args) table_name, old_name, new_name = args [:rename_column, [table_name, new_name, old_name]] end
# File lib/active_record/migration/command_recorder.rb, line 192 def invert_rename_index(args) table_name, old_name, new_name = args [:rename_index, [table_name, new_name, old_name]] end
# File lib/active_record/migration/command_recorder.rb, line 175 def invert_rename_table(args) [:rename_table, args.reverse] end
# File lib/active_record/migration/command_recorder.rb, line 157 def invert_transaction(args) sub_recorder = CommandRecorder.new(delegate) sub_recorder.revert { yield } invertions_proc = proc { sub_recorder.replay(self) } [:transaction, args, invertions_proc] end
Forwards any missing method call to the target.
# File lib/active_record/migration/command_recorder.rb, line 282 def method_missing(method, *args, &block) if delegate.respond_to?(method) delegate.public_send(method, *args, &block) else super end end
# File lib/active_record/migration/command_recorder.rb, line 277 def respond_to_missing?(method, _) super || delegate.respond_to?(method) end