May 29 2008

DataMapper without a database

DataMapper is fast becoming a credible contender in the Ruby ORM field. The first - and only at this early stage - thing that temporarily disappointed me was the following scenario. 

class Foo
  include DataMapper::Resource

  property :id, Integer, :serial => true
  property :title, String
end

Running this produces ArgumentError: Unknown adapter name: default, suggesting that a database connection needs to be setup in order to use any objects that include the DataMapper::Resource module. This is something I would rather not have to do for my dependency neutral test suite, in which all calls to ORM objects are simulated using mocks.

I soon realized that DataMapper doesn't require a database connection to be present, but needs to know which adapter to use. If we're not interested in interacting with the database, using DataMapper::Adapters::AbstractAdapter does the trick. 

DataMapper.setup(:default, "abstract::")

class Foo
  include DataMapper::Resource

  property :id, Integer, :serial => true
  property :title, String
end

Foo.new(:title => "metal").title # => "metal"