has_many relationships

rubyonrails-talk
1

In my model I have two classes, a donation class and a good class. A donation can have mulitple goods, so I set up a has_many relationship between the two objects.

class Donation < ActiveRecord::Base   has_many :goods

class Good < ActiveRecord::Base   belongs_to :donation

In my view (donation/new.html.erb), I add goods to a donation the following way;

<input id="donation__goods_item" name="donation[goods][1][item]" style="width: 100%;" maxlength="20" type="text"> <textarea id="donation_goods_description" name="donation[goods][1] [description]" style="width: 100%;" rows="3"></textarea> <input id="donation__goods_item" name="donation[goods][2][item]" style="width: 100%;" maxlength="20" type="text"> <textarea id="donation_goods_description" name="donation[goods][2] [description]" style="width: 100%;" rows="3"></textarea> <input id="donation__goods_item" name="donation[goods][2][item]" style="width: 100%;" maxlength="20" type="text"> <textarea id="donation_goods_description" name="donation[goods][2] [description]" style="width: 100%;" rows="3"></textarea>

This will create the following @params after submitting the form.

{"commit"=>"Submit", "authenticity_token"=>"727eec63cfc5b40ee935c0d3478476661893b52c", "donation"=>{"goods"=> {"1"=> {"item"=>"books", "description"=>"Children books"},   "2"=> {"item"=>"shoes", "description"=>"Leather Boots"},   "3"=> {"item"=>"blankets", "description"=>"wool blankets"},}}}

The donation controller:

class DonationsController < ApplicationController   def create     @donation = Donation.new(params[:donation])     ....

So, I was hoping that ruby on rails automatically generates the goods and adds them to the donation object, but when create is called, i get the following error on the first line;

ActiveRecord::AssociationTypeMismatch in DonationsController#create

Good expected, got Array

Any help is appreciated.

2

There is a lot of magic in rails, but not that much.

Based on the @params info that you showed you will have to extract the donation info, create the object and manually make the relations to the goods.

ex def create   @donation = Donation.new(params[:donation])   params[:donation][:goods].each do |g|     @donation.gifts.build(g)   end

  if @donation.save      ..   end end

Or something like that.

3

Thanks. Is there some way to manipulate the @params info so that ruby automates this process?

4

Franz Obenhauser wrote:

Thanks. Is there some way to manipulate the @params info so that ruby automates this process?

On Jan 29, 1:21 pm, Chris Olsen <rails-mailing-l...@andreas-s.net>

I think I could explain this if I had to, but let me send you someplace better first and if that doesn't help come back. Railscasts had three excelent screen casts on doing exactly what your asking about, and they will be much better then a text answer I could write in the next 3 minutes.

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