Renaming table in rails

I want to rename a table... (any table.)

I tried this line of code:

ActiveRecord::ConnectionAdapters::SchemaStatements.r开发者_C百科ename_table(old_name, new_name)

Here's the weird thing. I know I got it working the first time, but now I get this error: undefined method `rename_table' for ActiveRecord::ConnectionAdapters::SchemaStatements:Module

Was there something I need to set?

Remember that in Rails >= 3.1 you can use the change method.

 class RenameOldTableToNewTable < ActiveRecord::Migration
   def change
     rename_table :old_table_name, :new_table_name
   end 
 end

You would typically do this sort of thing in a migration:

class RenameFoo < ActiveRecord::Migration
  def self.up
    rename_table :foo, :bar
  end

  def self.down
    rename_table :bar, :foo
  end
end

.rename_table is an instance method, not a class method, so calling Class.method isn't going to work. Instead you'll have to create an instance of the class, and call the method on the instance, like this: Class.new.method.

[EDIT] In this instance, ActiveRecord::ConnectionAdapters::SchemaStatements isn't even a class (as pointed out by cam), which means that you can't even create an instance of it as per what I said above. And even if you used cam's example of class Foo; include ActiveRecord::ConnectionAdapters::SchemaStatements; def bar; rename_table; end; end;, it still wouldn't work as rename_table raises an exception.

On the other hand, ActiveRecord::ConnectionAdapters::MysqlAdapter is a class, and it is likely this class you'd have to use to rename your table (or SQLite or PostgreSQL, depending on what database you're using). Now, as it happens, ActiveRecord::ConnectionAdapters::MysqlAdapter is already accessible through Model.connection, so you should be completely able to do Model.connection.rename_table, using any model in your application. [/EDIT]

However, if you wish to permanently rename a table, I would suggest using a migration to do it. It's easy and the preferred way of manipulating your database structure with Rails. Here's how to do it:

# Commandline
rails generate migration rename_my_table

# In db/migrate/[timestamp]_rename_my_table.rb:
class RenameMyTable < ActiveRecord::Migration
  def self.up
    rename_table :my_table, :my_new_table
  end

  def self.down
    rename_table :my_new_table, :my_table
  end
end

Then, you can run your migration with rake db:migrate (which calls the self.up method), and use rake db:rollback (which calls self.down) to undo the migration.

ActiveRecord::Migration.rename_table(:old_table_name, :new_table_name)