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Craft GraphQL APIs in Elixir with Absinthe

Non-null Constraints

Explore how to enforce non-null constraints on GraphQL arguments using the Absinthe non_null macro. Understand why marking inputs as mandatory improves API validation, error handling, and schema accuracy for more robust GraphQL queries and mutations.

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Marking arguments as non-null

Exclamation marks are used in variable declarations to ensure that variable values are provided:

C++
query ($filter: MenuItemFilter!) {
   menuItems(filter: $filter) {
     name
   }
}

The document here declares that the $filter variable is a MenuItemFilter. Adding an exclamation mark denotes a mandatory value. This is a constraint that the document designer builds into the query, but the schema designer can also enforce non_null ...