Validate has_many relationship with conditions ?

rubyonrails-talk
1

I need to validate that I have at least one relationship with a certain condition. My code so far:

class User < ActiveRecord::Base   belongs_to :user_type end

class UserType < ActiveRecord::Base   has_many :users   has_many :admins, :source => :users, :conditions => "user_type_id = 1" end

How do I validate that I have at least one admin when updating any user?

2

You can overwrite validate_on_update in your User model.

http://api.rubyonrails.org/classes/ActiveRecord/Validations.html#M001044

I'm not sure if this is exactly what you're looking to do, but it might look something like: def validate_on_update     errors.add("User Type", "has no admins") if UserType.admins.count == 0 end

*warning, not tested*

3

Thanks, I got pretty close with this suggestion..

turns out as I build this out more, i actually have users, groups, and roles (on these groups), with role_types (1 is admin). in my roles controller, I have actions which add/remove roles from a given group (which correctly triggers my custom before_destroy method). However, I can't seem to find how to display the errors from "before_destroy" upon the redirect back to the group page. So far, I've been using "error_messages_for :groups", similar to on my forms. I'm guessing their is a problem displaying the errors generated by a "Role" in the "Group" pages. suggestions?

class User < ActiveRecord::Base   has_many :roles   has_many :groups, :through => :roles end

class Group < ActiveRecord::Base   has_many :roles   has_many :users, :through => :roles   has_many :owners, :through => :roles, :source => :user, :conditions => "role_type_id = 1" end

class RoleType < ActiveRecord::Base   has_many :roles end

class Role < ActiveRecord::Base   belongs_to :user   belongs_to :group   belongs_to :role_type

  def before_destroy     if (role_type_id.to_i == 1 && Group.find(group_id.to_i).owners.count <= 1)       errors.add(:group, "Groups require at least one owner")       false     end   end end

class RolesController < ApplicationController   def remove (group_id = params[:group_id], role_type_id = params[:role_type_id], user_id = @current_user.id)     conditions = {:group_id => group_id, :role_type_id => role_type_id, :user_id => user_id }     Role.destroy_all(conditions)     redirect_to :controller => :groups, :action => "show", :id => group_id   end end

gsterndale wrote: