What is the down migration for adding a polymorphic reference

Question

I have the folowing migration but don't know what to use in the down method

change_table :addresses do |t|
  t.references :addressable, :polymorphic => true
end

rbxbx · Answer 1 · 2013-02-18T21:38:05.530

16

actually,

   change_table :addresses do |t|
     t.remove_references :addressable
   end

would be a bit railsier, no?

edit: As Eben Geer points out

   change_table :addresses do |t|
     t.remove_references :addressable, :polymorphic => true
   end

is the correct way to do this. Cheers!

edited Feb 18 '13 at 21:38

answered Nov 20 '09 at 22:24

rbxbx

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1

this will cause the addressable_type column to be left behind. it should be t.remove_references :addressable, :polymorphic => true – Eben Geer Dec 14 '11 at 07:54
I would upvote this answer if it included @EbenGeer his comment – Arjan Feb 07 '13 at 12:37

score 10 · Answer 2 · answered Aug 31 '15 at 21:17

10

class RemoveAddressableFromAddresses < ActiveRecord::Migration
  def change
    remove_reference :addresses, :addressable, polymorphic: true, index: true
  end
end

answered Aug 31 '15 at 21:17

Judd

116
1
5

Please take a minute to explain what your code does and how it answers this question. – Bond Sep 01 '15 at 00:20
This should now be the correct answer: remove_reference can nowadays (since Rails 4.2 at least) be rolled back. That means, Rails knows how to roll back a remove_reference by a add_reference. So this code can be rolled back (though data may by lost in the migration) – Martin M Nov 22 '19 at 08:23

score 7 · Answer 3 · answered Dec 14 '11 at 07:57

7

def self.down
  change_table :addresses do |t|
    t.remove_references :addressable, :polymorphic => true
  end
end

answered Dec 14 '11 at 07:57

Eben Geer

3,696
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score 2 · Accepted Answer · answered Oct 03 '09 at 10:10

2

What's the problem?

def self.down
  remove_column :addresses, :addressable_type
  remove_column :addresses, :addressable_id
end

answered Oct 03 '09 at 10:10

Leonid Shevtsov

14,024
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are you saying remove_column :addresses, :addressable is not correct? – Damian Oct 03 '09 at 21:40
Damian: no, just look at the table via some SQL browser and you will see the two columns. – Leonid Shevtsov Oct 04 '09 at 13:26

Mark A. Nicolosi · Answer 5 · 2009-10-03T02:07:59.130

-2

What's wrong with this?

def self.down
  remove_column :addresses, :addressable
end

edited Oct 03 '09 at 02:07

answered Oct 02 '09 at 22:59

Mark A. Nicolosi

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Thats what I thought it would be but this is the first time i have used polymorphic models and got confused – Damian Oct 02 '09 at 23:07
actually it shouldn't it be remove_column :addresses, :addressable – Damian Oct 02 '09 at 23:08
Oops, you're totally right. I should have checked the docs first, instead of going by memory. – Mark A. Nicolosi Oct 03 '09 at 02:08

What is the down migration for adding a polymorphic reference

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