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Product Update

Introducing OneSchema Code Hooks

Code Hooks makes OneSchema even more flexible for use cases with unique business logic. Empower your engineering team to generate tailored functions to reformat, transform, and/or validate data.

Bobby Zhang

Bobby is the Designer at OneSchema.

February 17, 2023

Engineering and product teams use OneSchema to easily launch delightful spreadsheet import experiences. Because our customers span a variety of industries, we often see workflows that come with unique business logic built into their specific datasets. 

To make OneSchema even more flexible for these custom use cases, we’ve created OneSchema Code Hooks. Code Hooks empower your engineering team to generate tailored functions to reformat, transform, and/or validate data specific to your business's needs inside of the importer flow. 

There are three types of Code Hooks, which each execute at a different point during the import process: 

  1. Post-upload
  2. Post-mapping
  3. Validation 

Visit our Code Hooks docs page to learn more about Code Hooks and see some example code snippets.

Code Hooks example use cases


Post-upload Code Hooks modifies data right after it’s been uploaded. Your user’s uploaded file arrives in a nested format. Before it can be processed through OneSchema, you want to flatten it into something more usable.


Post-mapping Code Hooks transform data after the uploaded columns have been mapped to a template. A common use case we’ve seen is to split and merge columns prior to import (eg. Full name -> First name, Last name). You can also use post-mapping code hooks for deleting columns and adding empty columns (plus filling it with a particular value).


Validation Code Hooks surface errors and warnings on individual cells during the Review & Finalize pane. A common example of when this is helpful is to check for multi-column uniqueness – this will flag when values in separate columns that are paired up appear in more than one row of the dataset.

Validation Code Hooks can also be used for: 

  • Multi-column validations (row constraints) to check a cell in column X against a cell in column Y
  • Multi-row validations to check a cell in row X against a cell in row Y
  • Updating text shown to customers in the popup for a certain validation
  • Adding a warning to a cell

Learn more about implementing a Code Hook via our API Reference.

Tell us what you think

As always, we welcome your feedback on these changes! Please feel free to share feedback by reaching out to We'd also love to keep in touch on LinkedIn.

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