Q21: How do you implement a Custom Scalar in GraphQL?
When built-in primitives are insufficient, custom scalars (e.g., Date, JSON, URL) can be defined in SDL and provided custom logic for:
serialize: Converts back-end output to JSON.parseValue: Parses variables sent in JSON requests.parseLiteral: Parses inline AST literal values inside queries.
Key Takeaways
- Custom scalars validate and transform specialized datatypes at the framework boundary.
Knowledge Check
Which custom scalar method parses inline literal values written directly inside a query string?