parse a string into tokens in Shopify Liquid - parsing

Question

I have the following string ("my_str") in a Shopify metafield:
a:3,b:1,c:2,d:2,e:2,f:2
The keys are product variant IDs (shortened to a, b, c...) and the numbers are quantities.
I need to parse it into key:value pairs so I can do something like this with it:
{% assign my_str = collection.metafields.local.my_metafield %}
{% assign my_map = my_str | parse ???? %}
{% for product in collection.products %}
{% assign temp_qty = 1 %}
{% for pair in my_map %}
{% if pair[0] == product.variants.first.id %}
{% assign temp_qty = pair[1] %}
{% endif %}
{% endfor %}
<input type="hidden" id="abc-{{ forloop.index0 }}" value=temp_qty />
{% endfor %}
I definitely don't know how to parse my_str. I'm also open to suggestions about the best approach overall.

Answer 1

Liquid is pretty limited when it comes to creating arrays. The common approach is to use the split string filter.
In your case, it would look something like this:
{% assign my_str = 'a:3,b:1,c:2,d:2,e:2,f:2' %}
{% assign my_arr = my_str | split: ',' %}
{% for pair_str in my_arr %}
{% assign pair_arr = pair_str | split: ':' %}
ID: {{ pair_arr[0] }} Qty: {{ pair_arr[1] }} <br />
{% endfor %}
This blog post is also an interesting read on the topic of Liquid arrays: Advanced Arrays in Shopify's Liquid