2026-06-24 · 6 min read · Rahul Chitturi
- matlab
- json
- api
MATLAB structs often become the handoff format between analysis code, simulation scripts, and web APIs. The conversion looks simple until a nested struct, vector, or field name lands differently than the receiving service expects.
Before changing the model or backend contract, isolate the payload shape. Most bugs come from arrays that should be objects, objects that should be arrays, or numeric values that were rounded or serialized as strings.
Check the shape first
The API usually cares more about structure than formatting. Compare the converted JSON against a known-good payload and confirm every nested level has the expected type. A single MATLAB scalar struct can become an object, while a struct array becomes an array of objects.
- Confirm whether the endpoint expects an object or an array
- Check nested structs before looking at individual values
- Keep field names stable across MATLAB scripts and API docs
- Watch for empty arrays, missing fields, and optional sections
Do not hide numeric drift
Simulation outputs may include floating-point values with more precision than humans want to read. Formatting for review is fine, but do not round values before the API contract says they can be rounded. If the backend validates ranges, record the exact numeric representation sent over the wire.
Make field names web-friendly
MATLAB naming habits do not always match JSON API conventions. A service may expect camelCase, snake_case, or a documented acronym. Convert names intentionally instead of fixing failures one field at a time after integration tests start failing.
- Document the external JSON field names beside the MATLAB source
- Avoid spaces, units, or display labels in machine field names
- Keep units explicit in names or metadata, not in guessed comments
- Diff generated payloads after any script refactor
A Flashman workflow
Use the MATLAB struct converter to inspect the JSON shape, format the result with the JSON tool, then diff it against a saved fixture from the API team. This gives both sides a concrete payload to discuss before anyone changes production code.
Flashman runs the conversion in your browser, which helps when simulation payloads include proprietary labels or internal model parameters. Redact secrets and customer identifiers before sharing examples.