acts_as_shopping_cart

A simple shopping cart implementation.

You can find an example application here.

Install

Rails 3

Include it in your Gemfile

gem 'acts_as_shopping_cart', '~> 0.1.4'

And run bundler

bundle install

Usage

You need two models, one to hold the Shopping Carts and another to hold the Items

You can use any name for the models, you just have to let each model know about each other.

Examples

For the Shopping Cart:

class Cart < ActiveRecord::Base
  acts_as_shopping_cart_using :cart_item
end

For the items:

class CartItem < ActiveRecord::Base
  acts_as_shopping_cart_item_for :cart
end

or, if you want to use convention over configuration, make sure your models are called ShoppingCart and ShoppingCartItems, then just use the shortcuts:

class ShoppingCart < ActiveRecord::Base
  acts_as_shopping_cart
end

class ShoppingCartItem < ActiveRecord::Base
  acts_as_shopping_cart_item
end

Migrations

In order for this to work, the Shopping Cart Item model should have the following fields:

create_table :cart_items do |t|
  t.shopping_cart_item_fields # Creates the cart items fields
end

Shopping Cart Items

Your ShoppingCart class will have a shopping_cart_items association that returns all the ShoppingCartItem objects in your cart.

Add Items

To add an item to the cart you use the add method. You have to send the object and the price of the object as parameters.

So, if you had a Product class, you would do something like this:

@cart = Cart.create
@product = Product.find(1)

@cart.add(@product, 99.99)

In the case where your product has a price field you could do something like:

@cart.add(@product, @product.price)

I tried to make it independent to the models in case you calculate discounts, sale prices or anything customized.

You can include a quantity parameter too.

@cart.add(@product, 99.99, 5)

In that case, you would add 5 of the same products to the shopping cart. If you don't specify the quantity 1 will be assumed.

Remove Items

To remove an item from the cart you can use the remove method. You just have to send the object and the quantity you want to remove.

@cart.remove(@product, 1)

Empty the cart

To remove all the items in the cart at once, just use the clear method

@cart.clear

Total

You can find out about the total using the total method:

@cart.total # => 99.99

Taxes

Taxes by default are calculated by multiplying subtotal times 8.25

If you want to change the way taxes are calculated, override the taxes method on your class that acts_as_shopping_cart.

Example:

class ShoppingCart < ActiveRecord::Base
  acts_as_shopping_cart

  def taxes
    (subtotal - 10) * 8.3
  end
end

If you just want to update the percentage, just override the tax_pct method.

class ShoppingCart < ActiveRecord::Base
  acts_as_shopping_cart

  def tax_pct
    3.5
  end
end

Shipping Cost

Shipping cost will be added to the total. By default its calculated as 0, but you can just override the shipping_cost method on your cart class depending on your needs.

class ShoppingCart < ActiveRecord::Base
  acts_as_shopping_cart

  def shipping_cost
    5 # defines a flat $5 rate
  end
end

Total unique items

You can find out how many unique items you have on your cart using the total_unique_items method.

So, if you had something like:

@cart.add(@product, 99.99, 5)

Then,

@cart.total_unique_items # => 5

Development

Install the dependencies

bundle install

Test

Run rspec

rspec spec

Run cucumber features

cucumber

Both:

rake

About the author

Crowd Interactive is a leading Ruby and Rails consultancy firm based in Mexico currently doing business with startups in the United States. We specialize in building and growing Rails applications, by increasing your IT crew onsite or offsite. We pick our projects carefully, as we only work with companies we believe in.