find_by_id isn't working

Could you attach some code and some data to reproduce the error? It works fine for me

ruby-1.9.2-rc2 > xpto = Project.first
=> # ruby-1.9.2-rc2 > xpto.id
=> 1 ruby-1.9.2-rc2 > Project.find(1)
=> # ruby-1.9.2-rc2 > Project.find_by_id(1)
=> # ruby-1.9.2-rc2 >

ruby-1.9.2-rc2 > xpto = Project.first
 => #<Project id: 1, title: nil, due_date: nil, created_at: "2010-07-27 19:08:51", updated_at: "2010-07-27 19:08:51"> 
ruby-1.9.2-rc2 > xpto.id
 => 1 
ruby-1.9.2-rc2 > Project.find(1)
 => #<Project id: 1, title: nil, due_date: nil, created_at: "2010-07-27 19:08:51", updated_at: "2010-07-27 19:08:51"> 
ruby-1.9.2-rc2 > Project.find_by_id(1)
 => #<Project id: 1, title: nil, due_date: nil, created_at: "2010-07-27 19:08:51", updated_at: "2010-07-27 19:08:51"> 
ruby-1.9.2-rc2 >

Sorry for the delay. Just found the problem: my table pk isn't "id", it is "foo_id" and I map it using set_primary_key "foo_id" (and because you defined as just "id", it works for you). The question is, isn't a expected behavior to get a "find_by_id" always?

you want find_by_id to be like a find_by_your_primary_key???.
find_by_something looks for a column called something

Santiago, I found this after a while, but to me, just feel right to use "find_by_id", since even if my primary_key column isn't called "id", the attribute is mapped to just "id".

Btw, this really isn't a "bug", its more like a wish.

changing find_by_id to a some kind of find_by_primary_key seems awfull to me. I really dont like this change.
the find_by_something is clearly for db attributes. in your case id is just not an attribute in the database. Finding by primary key is simply just find.

Aliasing an attribute also does not work with the finder magic. See example below.
If you set a custom primary key then the attribute id is also only an alias.
So why the heck should this work?

class MyModel < ActiveRecord::Base
  # has a column name
  alias_attribute :some_name, :name
end

MyModel.finy_by_some_name('Egon') # does not work, cause some_name is no db attribute

I agree that find_by_primary_key is a bad idea, but when you have "foo.bar_id" as primary key, active record automatically aliases it to "foo.id", so one would expect find_by_id to work as well.

if the dynamic finders are changed so that find_by_id works even if the primary_key is foo_id then this change should support aliasing as a whole. it would only be consistent.