Make a column data unique for each user_id

This is my setup. I have a table user where all user with password and
so
on are set. The customer table has some customer related data. The
user_id
is the foreign key to relate the customers to the user.

On of the column in the customer table is the customernumber. These
numbers
has to be uniq for each user_id.

class Customers

belongs_to :user
end

class Users
has_many :customers
end

For example.

customer | customernumber | user_id
1 0001 1
2 0002 1
3 0001 2
4 0001 3
5 0002 3

How can i approach this? Any hints what I have to look for?

thanks in advance
best regards
denym

On Sat, May 18, 2013 at 8:14 AM, Denny M. [email protected]
wrote:

This is my setup. I have a table user where all user with password and so on
are set. The customer table has some customer related data. The user_id is
the foreign key to relate the customers to the user.

On of the column in the customer table is the customernumber. These numbers
has to be uniq for each user_id.

Is this a legacy database you’re trying to use with Rails? It doesn’t
appear to follow Rails conventions.

In this example, is “customer” a unique auto-generated identifier? If
so, why do you need “customernumber” to also be unique? If not,
what is it?

customer | customernumber | user_id
1 0001 1
2 0002 1
3 0001 2
4 0001 3
5 0002 3


Hassan S. ------------------------ [email protected]
http://about.me/hassanschroeder
twitter: @hassan

On Saturday, 18 May 2013 11:14:35 UTC-4, Denny M. wrote:

belongs_to :user
1 0001 1
2 0002 1
3 0001 2
4 0001 3
5 0002 3

How can i approach this? Any hints what I have to look for?

validates_uniqueness_of has a ‘scope’ option that will do exactly what
you’re describing:

class Customer < ActiveRecord::Base
belongs_to :user
validates_uniqueness_of :customernumber, :scope => :user_id
end

Depending on what you’re intending to use the customer number for, you
may
also want to take a look at something like acts_as_list.

–Matt J.

Matt J. wrote in post #1109607:

On Saturday, 18 May 2013 11:14:35 UTC-4, Denny M. wrote:

belongs_to :user
1 0001 1
2 0002 1
3 0001 2
4 0001 3
5 0002 3

How can i approach this? Any hints what I have to look for?

validates_uniqueness_of has a ‘scope’ option that will do exactly what
you’re describing:

Also note that any use of validates_uniqueness_of should also be backed
by unique constraints in the database to prevent race conditions from
causing duplicates.

For more details on race conditions related to uniqueness validations
read the section under “Concurrency and integrity” here:

http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#method-i-validates_uniqueness_of