Writing to Customer Metafields from Checkout UI Extension for Cart Validation in Functions

Extensions
1

Hi,​

I am currently implementing validation during the checkout process using Shopify Functions. Specifically, I aim to reference customer metafields within the Function to enforce certain conditions across multiple carts.​

While I can access customer metafields in Shopify Functions, I’m uncertain how to write data to these metafields from a Checkout UI Extension. Additionally, since the validation needs to span multiple carts, utilizing cart attributes isn’t suitable for this scenario.​

Could you please advise on how to write to customer metafields from a Checkout UI Extension, or suggest alternative approaches to achieve cross-cart validation?​

Thank you in advance for your assistance.

1 Like
2

Hey @tokujirou

For managing metafields in checkout ui extensions, the useApplyMetafieldsChange hook should work for writing to customer metafields from your Checkout UI Extension. Check out the metafields documentation (Metafields) which walks through how to implement this functionality.

For your cross-cart validation needs, just remember that the customer needs to be logged in for this approach to work properly. This ensures their metafields can be consistently accessed and updated across multiple cart sessions.

3

Thank you for your response! @KyleG-Shopify

I tried implementing the approach you suggested, but it seems that the metafield updates made from the Checkout UI Extension are not being reflected when accessed from the validation function.

Here’s what I specifically tried:

  1. Within the Checkout UI Extension, I used useApplyMetafieldsChange to update a customer metafield when the user performed a certain action. I tried both type: "updateMetafield" and type: "updateCartMetafield".
  2. In the cart validation function (run.graphql), I attempted to read the metafield value using both input.cart.buyerIdentity.customer.metafield.value and input.validation.metafield.value, and trigger an error if either had a value.

Is there anything I might be doing incorrectly with this approach?
Any insights would be greatly appreciated.

Thanks again for your help!