(Newb alert) One-to-many...

[Ken D'Ambrosio]

Hey!  I'm decent at Ruby, but pretty darn new to Rails.  Working through some tutorial stuff, and don't fully understand what direction to take.  I want to create a one-to-many association; how do I accomplish this?  Do I create the association with MySQL (the DB I'm using) first, and then just have Rails take advantage of it?  Do I use "migration" (which I only kinda-sorta "get")?  Or is there some other mechanism entirely?

Apologies for how dumb this probably sounds; trying to get the full feel of Rails, and there are definitely some places I'm still not quite understanding the concepts.

Thanks,

-Ken

[Hassan Schroeder]

On Mon, Feb 10, 2014 at 8:50 AM, Ken D'Ambrosio
<flyingtoa...@gmail.com> wrote:
> I want to create a one-to-many association; how do I accomplish this?

Have you read these?

http://guides.rubyonrails.org/association_basics.html
http://guides.rubyonrails.org/migrations.html

In general you should make changes to your DB through migrations
only, so you can reverse, repeat, insure identical changes are made
to other (deployment) systems, etc.

--
Hassan Schroeder ------------------------ hassan.s...@gmail.com
http://about.me/hassanschroeder
twitter: @hassan

[Colin Law]

On 10 February 2014 16:50, Ken D'Ambrosio <flyingtoa...@gmail.com> wrote:
> Hey! I'm decent at Ruby, but pretty darn new to Rails. Working through
> some tutorial stuff, and don't fully understand what direction to take. I
> want to create a one-to-many association; how do I accomplish this?

Work right through a good tutorial such as railstutorial.org (free to
use online) and all the basics (including associations) will become
clear.

Colin

[James Turley]

Example: an owner has many cats.

In your Cat model, add the line: 

belongs_to :owner

in your Owner model, add the line:

has_many :cats

You then need to run a migration on your cats table, to add the foreign key for owners, so Rails can build the associations. From the command line:

rails g migration add_owner_id_to_cats owner_id:integer

This should create a migration file (in the /db folder), with something like the following in it: 

class AddFooToPosts < ActiveRecord::Migration

  def change

    add_column :cats, :owner_id, :integer # ie, table, field name, field type

  end

end

then, run your migration.

rake db:migrate

Thanks to the convention over configuration approach, rails will automagically work out that owner_id is a foreign key to the owners table. from there, you'll be able to access cats through owners, and owners through cats:

mog.owner # "Steve"

steve.cats.first # "Mog"

That, of course, is just the tip of the iceberg - you can define all kinds of odd relations, and customise them as much as you want.

JT

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[James Turley]

NB: AddFooToPosts would be AddOwnerIdToCats, I just messed up the copy paste.