Rails 3 save multiple (constant) values of a checkbox selection to Single DB Column

Question

I have a constant called PAYMENT_METHODS in venue.rb.

PAYMENT_METHODS = {'Visa' => 1, 'MasterCard' => 2, 'American Express' => 3, 'Diners' => 4, 'JCB' => 5, 'Bankomat' => 6, 'sodexo' => 7, 'MA-Gutscheine' => 8 }

You can check/uncheck multipe payment types in a form (payment_options is a string):

<%= hidden_field_tag "venue[payment_options][]", nil %>
<% Venue::PAYMENT_METHODS.each do |key, value| %>
  <%= f.check_box :payment_options, {:multiple => true}, value %>
  <%= label_tag key %>
<% end %>

Now I want to save the values to the single Database Column payment_options, e.g. [1,3,5]. No matter what I check, it always saves 0. What am I doing wrong? I am using PostgreSQL.

Thanks in advance

You try to save a string to an int column?

Reactormonk
– Reactormonk

2012-03-19 11:17:08 +00:00
Commented Mar 19, 2012 at 11:17 — Reactormonk
– Reactormonk, Commented Mar 19, 2012 at 11:17

Sergio Tulentsev · Accepted Answer · 2012-03-20 07:04:48Z

2

You have several options here.

String column

Serialize this to a string and save to a VARCHAR column. There are many ways.

Examples:

update orders set payment_options = '1,2,3'; -- comma separated list    
update orders set payment_options = '{"visa": 1, "amex": 1}'; -- json object

Integer column

Store your selections as bits in a single int column.

Example:

VISA = 0x01
MASTERCARD = 0x02
AMEX = 0x04
DINERS = 0x08

update order set payment_options = #{VISA | MASTERCARD}; -- int value 3
update order set payment_options = #{MASTERCARD | DINERS}; -- int value 10

Then later you can check the value like this

def visa?
  (payment_options & VISA) == VISA
end

Flags and bitwise operations can be a little hard for you, if you never used them. Comma-separated list is probably the easiest choice.

Array column

Apparently, there are arrays in PostgreSQL, but I don't know much about this DB. Two previous options are universal and work in any database.

Many-to-many relationship

This had been covered zillion times. Keywords:

has_and_belongs_to_many
has_many :through

edited Mar 20, 2012 at 7:04

answered Mar 19, 2012 at 11:22

Sergio Tulentsev

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2 Comments

Lukas Hoffmann Over a year ago

thx! One general question: Do you think this is the right way to store payment types? I also thought about a PaymentTypemodel and a has_many_and_belongs_to_manyrelationship, but I think that is overkill...

Sergio Tulentsev Over a year ago

Depends on how you are going to use it. As far as I understand your intentions, yes, it would be an overkill.

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