From db32b545dadae7808c210cd7ceef949a620490f0 Mon Sep 17 00:00:00 2001 From: Aaron Patterson Date: Fri, 19 Nov 2010 11:20:02 -0800 Subject: [PATCH] adding Migration#change to the CHANGELOG --- activerecord/CHANGELOG | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG index 7f54c0fa30..f1e16ea2c1 100644 --- a/activerecord/CHANGELOG +++ b/activerecord/CHANGELOG @@ -1,5 +1,23 @@ *Rails 3.1.0 (unreleased)* +* Migrations can be defined as reversible, meaning that the migration system +will figure out how to reverse your migration. To use reversible migrations, +just define the "change" method. For example: + + class MyMigration < ActiveRecord::Migration + def change + create_table(:horses) do + t.column :content, :text + t.column :remind_at, :datetime + end + end + end + +Some things cannot be automatically reversed for you. If you know how to +reverse those things, you should define 'up' and 'down' in your migration. If +you define something in `change` that cannot be reversed, an +IrreversibleMigration exception will be raised when going down. + * Migrations should use instance methods rather than class methods: class FooMigration < ActiveRecord::Migration def up