Check whether you migrate up or down in Rails 3.1?

[Linus Pettersson]

Hi!

In Rails 3.1 there is only one method for migrations called 'change'.

I want to run some code in a migration only when migrating up, not down. Is that possible?

The issue I have is that this code is inside a migration file from Active Admin:

# Create a default user
AdminUser.create!(:email => 'ad...@example.com', :password => 'password', :password_confirmation => 'password')

So, when I try to migrate down this will fail because there is already a user present.

Any ideas?

Regards
Linus

[Peter Vandenabeele]

On Mon, Jan 2, 2012 at 10:49 PM, Linus Pettersson <linus.pe...@gmail.com> wrote:

Hi!

In Rails 3.1 there is only one method for migrations called 'change'.

Not exaclty. up and down still exist (but now instance methods instead of

class methods).

Google ("rails guide migrations").

 

I want to run some code in a migration only when migrating up, not down. Is that possible?

Yes.

 

The issue I have is that this code is inside a migration file from Active Admin:

# Create a default user
AdminUser.create!(:email => 'ad...@example.com', :password => 'password', :password_confirmation => 'password')

So, when I try to migrate down this will fail because there is already a user present.

And what about:

def up

  AdminUser.create!(:email => 'ad...@example.com', :password => 'password', :password_confirmation => 'password')

end

def down

  u = AdminUser.find_by_email('ad...@example.com')

  u.destroy

end

  

Any ideas?

If the down migration is really impossible to do (which can happen;

e.g because you miss data to reset everything to the original state)

than you can raise ActiveRecord::IrreversibleMigration exception

in the down migration.

HTH,

Peter

-- 

Peter Vandenabeele
http://twitter.com/peter_v

http://rails.vandenabeele.com

[Linus Pettersson]

I see.

Thank you very much Peter!

Regards

Linus