Pass Data Between Snippets and Sections Using {% render %} and {% capture %} in Shopify

Shopify developers often face challenges when trying to pass data between snippets and sections due to the isolated scope of the {% render %} tag. In one of my recent projects, I needed to share variables like sale_available between a snippet (tony-sale-availability.liquid) and a section (tony-slideshow.liquid).

In this post, I’ll show you how I tackled these challenges using the {% capture %} tag to grab snippet output and make it usable in sections. I’ll break down why {% render %} on its own falls short and how pairing it with {% capture %} and Liquid filters helped me create an effective solution.

The Problem with {% render %}

The {% render %} tag, which replaced {% include %} in Shopify, enforces isolated variable scopes. While this enhances modularity, it introduces challenges:

1. Variable Isolation:
   Variables declared or modified inside a snippet are not accessible in the parent section or template.
2. Explicit Data Passing:
   Data must be explicitly passed through the {% render %} tag, which becomes cumbersome when working with complex or dynamic values.
3. Limited Data Sharing:
   Scenarios involving multiple computed variables or dynamic data, like sale availability, require extra effort to make the data accessible beyond the snippet.

The Solution: Using {% capture %}

By using the {% capture %} tag, you can store the rendered HTML output of a snippet as a string and then parse it with Liquid filters to extract the necessary data. This approach allows you to handle various data types—such as booleans, strings, numbers, and more—enabling flexible data manipulation within your Shopify theme.

Step 1: The Snippet (tony-sale-availability.liquid)

Here’s the updated snippet that computes and renders HTML containing key sale information:

{%- assign selected_handle = settings.sale_dates -%}

{%- if selected_handle != blank -%}
  {%- assign sale_dates = shop.metaobjects.sale_dates[selected_handle] -%}

  {% if sale_dates %}
    {%- assign current_date = "now" | date: "%s" | plus: 0 -%}
    {%- assign start_datetime = sale_dates.start | date: "%s" | plus: sale_dates.start_time | date: "%s" -%}
    {%- assign end_datetime = sale_dates.end | date: "%s" | plus: sale_dates.end_time | date: "%s" -%}

    {% if current_date >= start_datetime and current_date <= end_datetime %}
      {%- assign sale_available = "true" -%}
    {% elsif current_date > end_datetime %}
      {%- assign sale_available = "false" -%}
    {% endif %}
  {% endif %}
{%- endif %}

<div id="sale-availability-status" style="display: none;">
  <span class="sale-available" data-sale-available="{{ sale_available }}">{{ sale_available }}</span>
</div>

Step 2: The Section (tony-slideshow.liquid)

To use the variables computed in the snippet within a section:

1. Capture the Rendered Snippet Output

{% capture sales_data %}
  {% render 'tony-sale-availability' %}
{% endcapture %}

2. Parse the Captured Data

Using Liquid filters, extract the required variables from the captured HTML:

{% assign sale_available = sales_data | split: '<span class="sale-available" data-sale-available="' | last | split: '">' | first %}

3. Use the Extracted Data

The extracted variables can now be used anywhere in the section:

<div id="tony-sale-availability-data">
  <p>Sale Available: {{ sale_available }}</p>
</div>

{% if sale_available == "true" %}
  <p>The sale is active!</p>
{% else %}
  <p>No sale is currently available.</p>
{% endif %}

Why {% render %} Alone Wasn’t Enough

The {% render %} tag encapsulates logic within a snippet, preventing variables from leaking into the parent scope. While this ensures modularity, it also limits dynamic data sharing between snippets and sections.

By combining {% render %} with {% capture %} and Liquid filters:

• Multiple Variables Can Be Accessed: You can store and parse HTML output to extract as many variables as needed.
• Dynamic Data Sharing Becomes Possible: Computed values like sale_available are made accessible to the parent scope.

Best Practices for Using {% capture %} and Snippets

1. Keep Snippets Modular:
   Snippets should focus on a single responsibility, like computing sale data.
2. Avoid Excessive Parsing:
   Parse only the data you need from the captured output to keep logic simple and efficient.
3. Document Your Approach:
   Clearly document the variables output by the snippet and their usage in sections for maintainability.

This method unlocks new possibilities for passing and using data between Shopify snippets and sections. Try it in your Shopify store and see how it simplifies dynamic data handling while keeping your codebase modular and maintainable. For more advanced techniques, explore Shopify’s Liquid documentation.