Question

Is it possible with datamapper to generate the models from an existing database schema? So, to do the inverse of a migration, which takes the models and generate the sql. What I want is given a database schema generate the models.

Answer 1

At last, I found that till now the best solution is to use dm-is-reflective plugin: https://github.com/godfat/dm-is-reflective.

It doesn’t generate the code for DataMapper models reflecting an existing database schema, but its properties access methods are automatically available (as long as you keep using this plugin, of course).

Here is an example of use:

require 'data_mapper'
require 'dm-is-reflective'

DataMapper.setup(:default, "postgres://user:pwd@localhost/db")

class Table
   include DataMapper::Resource

   is :reflective #activate dm-is-reflective

   reflect #reflects eeach property. You can be more specific (look at plugin documentation)
end

DataMapper.finalize

#Even if no field is defined, all of them are accessible
entry = Table.first(nil, {:id => 469})
print entry.anotherField