Magento2: value_index in configurable product API

Question

In official REST API guide Step 4. Define configurable product options, there are payload like below.

{
  "option": {
    "attribute_id": "141",
    "label": "Size",
    "position": 0,
    "is_use_default": true,
    "values": [
      {
        "value_index": 9
      }
    ]
  }
}

Other parameters I can understand, but what is the function of value_index?

The guide just said

The value assigned to the value_index must be unique within the system.

I have huge configurable products to create by the API, how can I make sure the value_index different in each creation?

Answer 1

"Value_index" is the configurable attribute option Id, which you want to use for this product . Simply it is configurable attribute's option id.

Answer 2

After a research, I found in Magento 1.9, the configurable product value_index is the configurable attribute option value, which could get by

$configurableAttributes = $product->getTypeInstance(true)->getConfigurableAttributesAsArray($product);
print_r($configurableAttributes);

In Magento 2, the configurable product value_index is the configurable attribute option value too.

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But, when use the Magento2 API, after my test, we could give the value_index some unique integer, like child product id, it will work too. We do not necessarily need the configurable attribute option value in the value_index.