OLD5 Bamboo Blog - Latest Comments in ActiveRecord != DataMapper

Re: ActiveRecord != DataMapper

solnic — Sun, 10 Feb 2008 07:36:00 -0000

Hey, nice comparison, I noticed one issue, this:

DataMapper::Base.auto_migrate!

has been changed into this:

DataMapper::Persistence.auto_migrate!

Cheers!

Re: ActiveRecord != DataMapper

Carl — Thu, 17 Jan 2008 17:14:00 -0000

@Matt & @Jonathan - Thanks for the explanation! DataMapper looks really cool and I'll try it out next time I start a merb app.

Re: ActiveRecord != DataMapper

Jonathan Conway — Thu, 17 Jan 2008 09:51:00 -0000

@carl - Properties are still attributes of a DM managed class however the difference is that DM manages their persistence.

@Matt + @thomas - I'm pretty sure the classic migrations aren't destructive (well they can be if so wished, or I might have misunderstood:)). A DM migration is just a class that inherits DataMapper::Migration in a similar way to Rails migrations. You can manipulate and change your schema/data anyway you wish in the 'up' and 'down' methods just like you can in Rails. Is this what you mean?

Cheers my dears

Jonathan

Re: ActiveRecord != DataMapper

James Urquhart — Thu, 17 Jan 2008 08:13:00 -0000

I was actually quite impressed with DataMapper. The documentation made sense, and the overview on the website was quite informative.

As for ActiveRecord, well i've had my ups and downs with that. The distinction between Model and the Migration was a bit annoying.

For example, when manipulating my schema via the Migration, i often had the associated Model break. Which is great if you are on the previous version, but the more versions behind you are, the more things can go wrong when upgrading - especially if you rely on methods in your models, or you decide to use another database and find that what worked in MySQL in version 1 totally barfs up with SQLite.

IMO, DataMapper is doing the right thing by sticking the schema in along with the model. That way i can think of versioning the Model as a whole.

Re: ActiveRecord != DataMapper

Matt — Thu, 17 Jan 2008 05:43:00 -0000

@Jon, true there are migrations in trunk but I presume they are still destructive so what benefit over auto_migrate do they provide (other than a history, which would be in your version control system)?

@Carl, I believe that a property defines an attribute, its type and the default value.

Re: ActiveRecord != DataMapper

Carl — Wed, 16 Jan 2008 15:00:00 -0000

One thing I don't understand about DataMapper is its usage of the terms property and attribute. When is something a property and when is it an attribute? This seems a little confusing.

Re: ActiveRecord != DataMapper

TomK32 — Wed, 16 Jan 2008 13:46:00 -0000

Jonathan, how good are Datamapper's migrations beyond the simple table creation? I mean like updating some counter cache I add at a later point?

Re: ActiveRecord != DataMapper

Jonathan Conway — Wed, 16 Jan 2008 11:57:00 -0000

DM's got classic migrations now (at least they're there in trunk)...