Rails - Jan 2012 - Check whether you migrate up or down in Rails 3.1?

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 =>
''admin-hcDgGtZH8xNBDgjK7y7TUQ@public.gmane.org'', :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

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On Mon, Jan 2, 2012 at 10:49 PM, Linus Pettersson <
linus.pettersson-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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 =>
''admin-hcDgGtZH8xNBDgjK7y7TUQ@public.gmane.org'', :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 =>
''admin-hcDgGtZH8xNBDgjK7y7TUQ@public.gmane.org
'', :password => ''password'', :password_confirmation
=> ''password'')
end

def down
  u =
AdminUser.find_by_email(''admin-hcDgGtZH8xNBDgjK7y7TUQ@public.gmane.org'')
  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

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I see.

Thank you very much Peter!

Regards
Linus

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