Rails table_name_prefix missing

You've define a method inside a module (Foo). This doesn't magically define that method on a class nested in that module.

I'd try something like

class Foo < ActiveRecord::Base  self.abstract_class = true  self.table_name_prefix = 'foo_'end

And then inherit from Foo

class Foo::Setting < Foo...end

This is probably caused by rails' autoloader. When doing this :

module Foo  class Bar  endend

And then trying to use Foo::Bar, the autoloader first tries to locate app/models/foo/bar.rb. The file is loaded, and module Foo is defined here (albeit as a module containing solely Bar) so the autoloader never attempts to load app/models/foo.rb.

This should only happen in development mode, as in production mode all of your files are require'd on startup.

There are two workarounds AFAIK :

Cheat the autoloader

declare your class using class Foo::Bar, to force the autoloader to resolve a constant lookup for Foo.

This has the annoying side effect that the constant lookup inside Bar will NOT be scoped inside Foo, for instance :

# app/models/foo.rbmodule Foo BAZ = "baz"end# app/models/foo/bar.rbclass Foo::Bar  def baz    BAZ  endend

here, Foo::Bar.new.bazwill fail, unless you reference the constant using Foo::BAZ. This can get really a mess when defining ActiveRecord associations, for instance.

Require the module

using require_dependency :

require_dependency 'foo'module Foo  class Bar  endend

This is IMHO the right solution, as it does not break the constant lookup, but it is also a bit annoying as you have to add the require statement on top of each namespaced file.

Note :

This bug seems to have been resolved in rails 4. I used the second workaround a lot while on rails 3, but I've tried to reproduce the bug in rails 4 and it does not show up anymore. I think they modified the way the autoloader works... For more info, see the rails guides on autoloading and reloading constants

I had the same issue. Solved it by changing either of my application's namespace or the model's.

Take a look at this question. Using the same namespace for the application as for models causes to models not pick up the parent namespace table_name_prefix correctly.