Ordered Sets in Ruby

Rails
#1

Hi all,

I am implementing a simple invoice system where I have invoiceLines,
and where I want to keep the order of the lines. I have tried to
google around but have not found any sample on this.

Can someone give me a pointer to something that uses a set where the
order is kept?

Thanks in advance.

Regards,

Fidel.

#2

On Sep 19, 2009, at 5:35 PM, Fidel V. wrote:

Regards,

Fidel.

Well, that would be an Array. Or in the likely case that your data is
accessed with ActiveRecord models, an AssociationProxy that will
behave mostly like an Array. You will probably find something like
the following in any reasonable discussion about the has_many/
belongs_to associations. If you don’t specify a default order for the
association, then you’ll get the invoice_lines back in whatever order
the database prefers (often the order in which the database records
were created).

Models

class Invoice < ActiveRecord::Base
has_many :invoice_lines, :order => ‘line_number’
end
class InvoiceLine < ActiveRecord::Base
belongs_to :invoice
end

migration (schema)

create_table :invoices do |t|
t.integer :number
t.date :inv_date
t.date :due_date

etc.

end

create_table :invoice_lines do |t|
t.references :invoice

equiv. to t.integer :invoice_id

t.integer :line_number
t.string :sku
t.integer :quantity
t.decimal :unit_price, :precision => 8, :scale => 2

etc.

end

use in a controller

@invoice = Invoice.find_by_number(params[:invoice][:number])

@invoice.invoice_lines
#=> an array-like set of InvoiceLine records

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

#3

Hi Rob,

Thanks for the reply. I have managed to get this code done. What I
wanted really was how to save and update.

For instance, I want to know how to create the instance of the
invoice, and the invoice lines. When updating the invoice, its line
items with the respective order should be also updated in the db.

If I remove one item from the list, the order of each item should be
adjusted.

Let’s say I have the following invoiceitems:

item, qty, price, order
1, 3, 12.0, 1
6, 1, 23.0, 2
3, 2, 11.0, 3

if I remove item with order 2, I should get the following:

1, 3, 12.0, 1
3, 2, 11.0, 2

What I am after is a view + controller solution.

Thanks in advance.

Regards,

Fidel.

On Sat, Sep 19, 2009 at 11:59 PM, Rob B.

#4

Take a look at acts_as_list - http://github.com/rails/acts_as_list

#5

On Sun, Sep 20, 2009 at 1:28 AM, E. Litwin [email protected]
wrote:

Take a look at acts_as_list - http://github.com/rails/acts_as_list

Hi Litwin,

I have cloned the git file to my hard drive, and tried running the
init.rb, but that has given me this error:

init.rb:3: uninitialized constant ActiveRecord::Base (NameError)

How do I install it?

Thanks in advance,

Fidel.

#6

Hi Litwin,

Thanks a lot for the link.

I will give it a try, but from what I saw that is exactly what I am
looking for.

Regards,

Fidel.

#7

Never mind,

Trial and error and managed to install it.

Thanks!

Fidel.

#8

Fidel V. wrote:

On Sun, Sep 20, 2009 at 1:28 AM, E. Litwin [email protected]
wrote:

Take a look at acts_as_list - http://github.com/rails/acts_as_list

Hi Litwin,

I have cloned the git file to my hard drive, and tried running the
init.rb, but that has given me this error:

init.rb:3: uninitialized constant ActiveRecord::Base (NameError)

How do I install it?

Use script/plugin install.

Thanks in advance,

Fidel.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

#9

Hi Marnen,

Thanks for the reply. I found that out through trial and error. I
first tried script/plugin install act_as_list, but that didn’t work.
So, I installed from github directly.

Thanks once again.

Regards,

Fidel

On Thu, Sep 24, 2009 at 12:16 PM, Marnen Laibow-Koser

#10

Yes!!!

Thanks!!!

Fidel.

On Thu, Sep 24, 2009 at 1:28 PM, Marnen Laibow-Koser

#11

Fidel V. wrote:

Hi Marnen,

Thanks for the reply. I found that out through trial and error. I
first tried script/plugin install act_as_list, but that didn’t work.
So, I installed from github directly.

Right. Script/plugin install takes a Git (or SVN) repository URL. It
pulls the code from the repo, installs it in the appropriate place, and
then runs init.rb. It’s magic!

Thanks once again.

Regards,

Fidel

On Thu, Sep 24, 2009 at 12:16 PM, Marnen Laibow-Koser

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]