On 4 March 2010 17:30, Hassan Schroeder <[email protected]> wrote:
>> Similarly, you can now no longer alter your models, because some
>> migrations rely on the operation of the model at that "point in time"
>
> Likewise, sorry, that makes zero sense to me. I can't alter a model
> because it was altered before? What??
>
> Maybe an example would help...
Yesterday I created this model and it's migration:
class Post < ActiveRecord::Base
end
class CreatePosts < ActiveRecord::Migration
def self.up
create_table :posts do |t|
t.string :summary
t.string :user_id
t.timestamps
end
# default record for Posts
Post.reset_column_information
Post.create(:name => "My First Post", :user_id => 1)
end
def self.down
drop_table :posts
end
end
Today I decide that I need to have an "expired flag" on my posts, and
it's required, so I create a new migration and edit my model:
class Post < ActiveRecord::Base
validates_presence_of :expires
end
class AlterPostsAddExpired < ActiveRecord::Migration
def self.up
add_column :posts, :expires, :datetime
end
def self.down
remove_column :posts, :expires
end
end
But now, when I roll back my migrations and try to roll them forward
again, the "create" breaks because the "point in time" Post record
*didn't* require an "expires" value (or indeed, even have a field for
it!).
As Rob says, the way around this is to duplicate the model code (or at
least the minimum you need to achieve your result) in the migration -
but this is a smelly, non-DRY, and non-testable way of putting data in
the tables (remember where I said it was "deliberately awkward" to do)
- when the alternative is to use a seed or seed-fu (like, 30 seconds
work), I can't believe you're making me go through these hoops to show
you how bad a practice it is to put data in your migrations
:-/
--
You received this message because you are subscribed to the Google Groups "Ruby
on Rails: Talk" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.
