How should I change his script so that it works for collections and not just one product in Shopify? - ruby

Question

The script is a template that comes with the script editor app in Shopify. I need to make it work so that if you buy one product from a collection, you get another one free from that collection. This script works only for buying the same product. Here is the script:
PAID_ITEM_COUNT = 2
DISCOUNTED_ITEM_COUNT = 1
# Returns the integer amount of items that must be discounted next
# given the amount of items seen
#
def discounted_items_to_find(total_items_seen, discounted_items_seen)
Integer(total_items_seen / (PAID_ITEM_COUNT + DISCOUNTED_ITEM_COUNT) * DISCOUNTED_ITEM_COUNT) - discounted_items_seen
end
# Partitions the items and returns the items that are to be discounted.
#
# Arguments
# ---------
#
# * cart
# The cart to which split items will be added (typically Input.cart).
#
# * line_items
# The selected items that are applicable for the campaign.
#
def partition(cart, line_items)
# Sort the items by price from high to low
sorted_items = line_items.sort_by{|line_item| line_item.variant.price}.reverse
# Create an array of items to return
discounted_items = []
# Keep counters of items seen and discounted, to avoid having to recalculate on each iteration
total_items_seen = 0
discounted_items_seen = 0
# Loop over all the items and find those to be discounted
sorted_items.each do |line_item|
total_items_seen += line_item.quantity
# After incrementing total_items_seen, see if any items must be discounted
count = discounted_items_to_find(total_items_seen, discounted_items_seen)
# If there are none, skip to the next item
next if count <= 0
if count >= line_item.quantity
# If the full item quantity must be discounted, add it to the items to return
# and increment the count of discounted items
discounted_items.push(line_item)
discounted_items_seen += line_item.quantity
else
# If only part of the item must be discounted, split the item
discounted_item = line_item.split(take: count)
# Insert the newly-created item in the cart, right after the original item
position = cart.line_items.find_index(line_item)
cart.line_items.insert(position + 1, discounted_item)
# Add it to the list of items to return
discounted_items.push(discounted_item)
discounted_items_seen += discounted_item.quantity
end
end
# Return the items to be discounted
discounted_items
end
eligible_items = Input.cart.line_items.select do |line_item|
product = line_item.variant.product
!product.gift_card? && product.id == 11380899340
end
discounted_line_items = partition(Input.cart, eligible_items)
discounted_line_items.each do |line_item|
line_item.change_line_price(Money.zero, message: "Buy one Bolur, get one Bolur free")
end
Output.cart = Input.cart
I tried changing, what seems to be the relevant code:
eligible_items = Input.cart.line_items.select do |line_item|
product = line_item.variant.product
!product.gift_card? && product.id == 11380899340
end
to this:
eligible_items = Input.cart.line_items.select do |line_item|
product = line_item.variant.product
!product.gift_card? && **collection.id** == 123
end
but I get an error:
undefined method 'collection' for main (Your Cart)
undefined method'collection' for main (No Customer)

Answer 1

Two things here:
line_item.variant.product does not have the property collections. For that, you want to use line_item.product (docs) – which (should...see point two) expose all of the methods and properties of the product object.
However, in my attempt to do something similar to you (discount based on product) I tried iterating over line_item.variant – and am always hitting the error of undefined method 'product' for #<LineItem:0x7f9c97f9fff0>. Which I interpret as "line_items accessed in cart scripts can only be at the variant level".
So, I wonder if this is because the cart only contains variants (product/color/size) – so we aren't actually able to access the line_items by product, and only by variant.
I tired iterating over line_item.product_id, which also throws a similar error. I think we just have to try to do some hacky thing at the variant level.
I am going to see if I can access the product by the variant ID...back to the docs!

Answer 2

You actually can't do a collection, so you'd need to modify the script to work with a product type or tags. That script will need to be heavily modified to work for a number of products and not multiples of the same