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Input Directives

While GraphQL doesn't natively support modifying query arguments and inputs through directives, Baeta provides a utility called Input Directives that enables this functionality.

Target Types​

Input directives can target different types of inputs:

  • scalar: For primitive values like numbers, strings, etc.
  • list: For array values
  • object: For complex object inputs

Defining Input Directives​

First, define your input directive in the schema:

src/modules/directives/input-directives.gql

directive @increment(by: Int!) on INPUT_FIELD_DEFINITION | ARGUMENT_DEFINITION

type Query {
  testIncrementDirective(value: Int! @increment(by: 1)): Int!
}

Implementing Input Directives​

Use the createInputDirective utility from @baeta/core to implement the directive's behavior:

src/modules/directives/input-directives.ts

import { createInputDirective } from "@baeta/core";
import type { Context } from "../../types/context";
import { getCustomInputDirectiveModule } from "./typedef";

const { $directive, Query } = getCustomInputDirectiveModule();

const incrementDirective = createInputDirective<{ by: number }, Context>({
  name: "increment",
  target: "scalar",
  resolve: ({ directiveConfig, getValue, setValue }) => {
    const value = getValue();
    if (typeof value === "number") {
      setValue(value + directiveConfig.by);
    }
  },
});

$directive(incrementDirective);

Query.testIncrementDirective(({ args }) => {
  return args.value;
});

How It Works​

The input directive processes the input value before it reaches the resolver:

  1. getValue() retrieves the original input value.
  2. The directive logic modifies the value.
  3. setValue() updates the input value.

Usage​

When querying, the directive will modify the input before it reaches the resolver:

query {
  testIncrementDirective(value: 5) {
    # value will be incremented to 6 before reaching the resolver
  }
}

This feature is particularly useful for input validation and data transformation.

For more examples and implementations, visit the Baeta directives examples.