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This question concerns three models:

Sale

class Sale < ActiveRecord::Base
  has_many :sale_items
  has_many :items, through :sale_items
end

Item

class Item < ActiveRecord::Base
  has_many :sale_items
  has_many :sales, :through => :sale_items
end

SaleItem

class SaleItem < ActiveRecord::Base
  belongs_to :sale
  belongs_to :item
end

To explain, an item acts as a base template for a sale_item. The application has many Items, but these are not necessarily a part of every Sale. So, sale_item.name actually points to sale_item.item.name, and sale_item's price method looks like this:

def price
  super || item.price
end

A sale_item either gets its price from its item, or that price can be overridden for that specific sale_item by editing its price column in the database.

This is what I'm having difficulty with in my sales/_form.html.erb view: I essentially need a table of all Item objects that looks the table in this Tinkerbin: http://tinkerbin.com/46T7JAKs.

So, what that means is that if an unchecked checkbox gets checked and the form is submitted, a new SaleItem needs to be created with an item_id equal to that if the Item from the list, and with appropriate price and quantity fields (quantity is specific to SaleItem and does not exist for Item objects).

Additionally, if the Sale that is being edited already includes a specific SaleItem, that checkbox should already be checked when the form view is rendered (so unchecking a box for a row would delete the SaleItem object associated with that Item and this Sale).

I'm not sure how this could be done—maybe I'm doing it wrong from the beginning. I toyed with the idea of doing away with the SaleItem model altogether and just creating a items_sales table with the fields sale_id, item_id, price, and quantity, but I'm not sure that is the best pattern.

Update

The previous solution I posted ended up with some flaws and failing tests. I finally figured it out, but will post the real solution shortly.

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4
  • Where exactly are you stuck? getting the checkbox to call the controller? what to write in the controller? Commented Nov 22, 2011 at 9:54
  • I essentially need to end up with multiple forms for each individual possible SaleItem, and this is what I can't figure out how to do. I'm not sure how to build the view. Commented Nov 22, 2011 at 9:59
  • You want this to be an on click action? meaning each checkbox clicked calls the controller to update, or do u want there to be a save button on the bottom which submits all changes? Commented Nov 22, 2011 at 10:02
  • I was planning on doing this with a single submit button at the bottom. Commented Nov 22, 2011 at 10:04

3 Answers 3

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1

As the author of cocoon, a gem that will make creating dynamically nested forms easier, I would like to point you to a sample project called cocoon_simple_form_demo, that contains all kinds of nested forms, including this type.

I have also written a blogpost describing all these.

Hope this helps.

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0

What you want to have is a checkbox tag with an array which will hold on submission an array of all selected id's, so instead of the html checkbox use the checkbox helper:

<%= check_box_tag 'sale_item_ids[]', item.id -%>

On submission the params hash will hold the ids of the selected item's. What you need to do now is loop on each of these and do the appropriate creation of the relationship (sale_item). You must also loop on those that exist already for this sale and delete them if they are not in the array submited.

Upon creating the actual html page you can check if the id of the checkbox is already in the sale and check/uncheck it accordingly.

Hope this helps :)

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1 Comment

Although it's the least detailed answer, it's the one that pointed me in the right direction and helped me get it solved. Thanks!
0

What if you treat the join table more like a normal rails model.

class SaleItems < ActiveRecord::Migration
def change
create_table :sale_items do |t|
  t.integer :sale_id
  t.integer :item_id
  t.float :price
  t.float :quantity

  t.timestamps
   end
  end
end

Then you can do things like

controller

@sale = Sale.new
@saleitem = @sale.SaleItem.build

You can add a item select for every line in the form. With some javascript you can update the price field from the item selected and change it if you want.

Even better than select, check out this railscast on auto complete association (if you don't have a pro account on railscast(get one!) go here

For adding lines til the Sale form take a look at this railscast on complex forms

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2 Comments

That's exactly what my SaleItems table already looks like. If I use @saleitem = @sale.SaleItem.build in my controller, that only gives me a finite amount of SaleObject items. I need the number of forms rendered on the page to scale according to how many total Item objects there are.
Hello. lend 10 minutes to Ryanrailscast 74. This show how to do it, but not with jQuery. Make a partial with <% fields_for "sale[sale_item_attributes][]", sale_item do |sale_item_form| %> and the fields you need. Then make a javascript link to generate more fields_for as you need.

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