ruby - Rails: Adding methods to ActiveRecord models -

i'm writing first rather simple ruby on rails (3.2) application. idea manage email accounts. schema rather simple:

t.string   "email" t.string   "password" 

the activerecord model defined as:

class mailuser < activerecord::base   attr_accessible :email, :password 

i've been using scaffolding form_for(@mailuser) , @mailuser.update_attributes(params[:mailuser]) magic. works well.

now quirk user should allowed edit user part (e.g. "foo") of email while domain (e.g. "example.org") must stay untouched. email field contains complete email address (e.g. "foo@example.org"). in edit form don't display fields

• email
• password

but rather

• userpart
• password

where userpart shown @mailuser.userpart (editable) + domain (not editable).

so thought i'd solve adding getter , setter user part this:

class mailuser < activerecord::base    attr_accessible :email, :password     # getter user part (left of '@')    def userpart       email.split('@')[0]    end     # setter user part (left of '@')    def userpart=(new_userpart)       email = email.sub(/(.+)@/, new_userpart+"@")    end 

in fact getting @mailuser.userpart works well. , it's displayed in form_for(@mailuser). problem occurs when saving form using @mailuser.update_attributes(params[:mailuser]) in controller's update method. rails apparently tries update @mailuser object attributes made available through attr_accessible. userpart attribute not reflect actual database field.

so wonder proper way add such methods activerecord models add functionality? i'm used pylons (a python mvc framework) , use such additional methods way.

(in fact wonder: can't split user , domain parts changing database schema. database used other applications i'm stuck way looks.)

thanks in advance.

you want add attr_accessible :userpart userpart can updated update_attributes mass assignment.

added: userpart example of virtual attribute if want ask mr. google more detailed explanation.