3.5 🌳 Let’s Create Data in Shopify

Why Pre-processor?

🔁 1. Dynamic Value Generation

👉 “System-generated fields”

Example:\
For every sync, you want to send a tag like:

ITEM-1, ITEM-2, ITEM-3

Why Pre-processor?\
Because this requires a counter (loop) — mapping cannot generate sequence-based values.

❓ 2. Conditional Field Inclusion

👉 “Send only if meaningful”

Example:\
Send product_type only when category exists

If category = “Clothing” → send
If category = null → don’t send

Why Pre-processor?\
Because this needs an if condition — mapping cannot decide whether to include/exclude fields.

🔄 3. Data Restructuring

👉 “Change format of data”

Example:\
Input:

["v1", "v2"]

Output:

[{"note": "v1"}, {"note": "v2"}]

Why Pre-processor?\
Because this requires changing structure (loop + transformation) — not just direct mapping.

“Whenever data needs to be generated, filtered, or reshaped, we use a Pre-processor.”

\
Scenario:

Assume you receive 3 products from an external system (PIM).

You need to:

Add tags → ITEM-1, ITEM-2, ITEM-3
Send product_type only if category exists
Convert notes into Shopify metafields structure

Step 1: Create the Workflow

Create a new Batch-type workflow

Step 2: Mock Source Data Using Code Runner

To keep things simple, simulate the PIM response. Add a Code Runner step. Paste the following code:

# Assign final output to variable “response” at the end.

response = [
 {
   "name": "Shirt",
   "category": "Clothing",
   "notes": ["v1", "v2"]
 },
 {
   "name": "Mug",
   "category": None,
   "notes": ["x1"]
 },
 {
   "name": "Notebook",
   "category": "Stationery",
   "notes": []
 }
]

Step 3: Add Loop

Add a Loop. Keep the cursor inside the iterable box and choose Code Runner Step from Data Hub -> {{1}}

👉 This loops through each product in the array

Step 4: Add Mapping (Shopify Create Product)

Search for Shopify (Beta)
Select your credentials
Select Create a New Product API and click Next
Payload Setup: Use loop item → {{2.items}}

Keep the cursor inside the payload box, click on plus icon before the loop and choose item from Data Hub. {{2.items}} is automatically populated. This means we are using every product (JSON object) as payload in API Call.

In the Data Hub, Add Mock Data for Code Runner

[
{
  "name": "",
  "category": "",
  "notes": []
},
 {
  "name": "",
  "category": "",
  "notes": []
}
]

Click on Add Mapping. name → title
Click on Save and Exit to return to the workflows page.

Step 5: Understand the Requirement

Data we have:

[
 {
   "name": "Shirt",
   "category": "Clothing",
   "notes": ["v1", "v2"]
 },
 {
   "name": "Mug",
   "category": null,
   "notes": ["x1"]
 },
 {
   "name": "Notebook",
   "category": "Stationery",
   "notes": []
 }
]

Data we want to send:

For first product creation,

{
  "product": {
    "title": "Shirt",
    "tags": "ITEM-1",
    "product_type": "Clothing",
    "metafields": [
      { "namespace": "custom", "key": "note", "value": "v1", "type": "single_line_text_field" },
      { "namespace": "custom", "key": "note", "value": "v2", "type": "single_line_text_field" }
    ]
  }
}

For second product creation,

{
  "product": {
    "title": "Mug",
    "tags": "ITEM-2",
    "metafields": [
      { "namespace": "custom", "key": "note", "value": "x1", "type": "single_line_text_field" }
    ]
  }
}

👉 Notice:

❌ product_type is NOT sent (because category = null)

For third product creation,

{
  "product": {
    "title": "Notebook",
    "tags": "ITEM-3",
    "product_type": "Stationery",
  }
}

👉 Notice:

❌ No metafields (because notes = empty)

Observing carefully what we have and what we expect:

Requirements:

Requirement 1: Generate “ITEM-\” and send it in Tags
Requirement 2: If category is null, don’t send product_type
Requirement 3: If notes are not empty, structure metafields as shown above; if empty, don’t send

Step 6: Add Pre-Processor

Now, let us implement these requirements one by one via the Pre-processor.

Requirement 1: Generate “ITEM-\” and send in Tags

Click on Add Pre-processor.

Let’s add the number based on the looping index. It starts from 0. Hence, we need to add 1 to it.

To use a looping index, we need to add it to inputs.

Give a variable name
For value, choose the index under plus icon of Loop Step in Data Hub.

In the screenshot, product_number is used as a variable.

The value needs to be incremented and sent in tags with prefix “ITEM-”, followed by the number.

To use the value of a variable, use inputs[“variable_name”].

You can copy paste the below code to your Preprocessor.

payload["tags"] = f"ITEM-{inputs['product_number']+1}"

Requirement 2: If category is null, don’t send product_type.

Click on Add under inputs. We need the product data (i.e., JSON object).

Keep the variable name as product_data
For value, choose the item under plus icon of Loop Step in Data Hub.

Now, in this product data:

If category is None, we should not send product_type
Otherwise, we should send it

To do that, add the below code to the Pre-processor

if inputs["product_data"].get("category"):
   payload["product_type"]=inputs["product_data"]["category"]

Requirement 3: Structure metafields

Since there are many usages of inputs[“product_data”]

To keep it simple, let us re-write as

payload["tags"] = f"ITEM-{inputs['product_number']+1}"
item = inputs["product_data"]
if item.get("category"):
   payload["product_type"]=item["category"]

Now, let us add the logic for metafields restructuring if notes exist:

if item.get("notes"):
   payload["metafields"] = [
       {
           "namespace": "custom",
           "key": "note",
           "value": note,
           "type": "single_line_text_field"
       }
       for note in item["notes"]
   ]

Cool, we have discussed some of the use cases of the Pre-processor.

Now, let us visualize the output.

Ensure that:

You have turned on console logs for the API Call step
You have checked Mapping & Modifiers Response

Save the workflow. Run the sync. Wait for a while, and then check the logs.

First API Request Information:

{
   "product": {
       "title": "Shirt"
   },
   "tags": "ITEM-1",
   "product_type": "Clothing",
   "metafields": [
       {
           "namespace": "custom",
           "key": "note",
           "value": "v1",
           "type": "single_line_text_field"
       },
       {
           "namespace": "custom",
           "key": "note",
           "value": "v2",
           "type": "single_line_text_field"
       }
   ]
}

Second API Request Information:

{
   "product": {
       "title": "Mug"
   },
   "tags": "ITEM-2",
   "metafields": [
       {
           "namespace": "custom",
           "key": "note",
           "value": "x1",
           "type": "single_line_text_field"
       }
   ]
}

Third API Request Information:

{
   "product": {
       "title": "Notebook"
   },
   "tags": "ITEM-3",
   "product_type": "Stationery"
}