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Custom scalars vs custom schema directives

See original GitHub issue

At the moment, I’m working on a GraphQL API architecture for my app. And I’m interested in pros and cons in using custom scalars vs. custom schema directives for validation (in the limitations and potential flexibility of each of these approaches).

See, e.g. @okgrow/graphql-scalars for a library of custom GraphQL scalar types for creating precise type-safe GraphQL schemas.

@confuser Did I understand correctly that @constraint directive from graphql-constraint-directive package can only be applied to INPUT_FIELD_DEFINITION, while there are many places where directives (in general) can be applied (see the full list here:

Issue Analytics

  • State:open
  • Created 5 years ago
  • Comments:5 (2 by maintainers)

github_iconTop GitHub Comments

FluorescentHallucinogencommented, Apr 10, 2019


As for the my custom scalars vs. custom schema directives for validation question, I’ve deep dived into how this package works and realized that it uses custom scalar types under the hood (wraps the field to which the directive is applied into custom scalars). So these are essentially equivalent things. Right?

robross0606commented, Mar 4, 2021

@FluorescentHallucinogen, this is my understanding as well. From what I can tell, the directives are run through a GraphQL transform using graphql-toosl/utils mapSchema() and end up being replaced by generated scalars.

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