Directives
Configure GraphQL types, fields, and arguments
A directive decorates part of a GraphQL schema or operation with additional configuration. Tools like Apollo Server (and Apollo Client) can read a GraphQL document's directives and perform custom logic as appropriate.
Directives are preceded by the @
character, like so:
type ExampleType {
oldField: String @deprecated(reason: "Use `newField`.") newField: String
}
This example shows the @deprecated
directive, which is a default directive (i.e., it's part of the GraphQL specification). It demonstrates the following about directives:
- Directives can take arguments of their own (
reason
in this case). - Directives appear after the declaration of what they decorate (the
oldField
field in this case)
Valid locations
Each directive can only appear in certain locations within a GraphQL schema or operation. These locations are listed in the directive's definition.
For example, here's the GraphQL spec's definition of the @deprecated
directive:
directive @deprecated(
reason: String = "No longer supported"
) on FIELD_DEFINITION | ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION | ENUM_VALUE
This indicates that @deprecated
can decorate any of the four listed locations. Also note that its reason
argument is optional and provides a default value. Usage examples of each location are provided below:
# ARGUMENT_DEFINITION
# Note: @deprecated arguments _must_ be optional.
directive @withDeprecatedArgs(
deprecatedArg: String @deprecated(reason: "Use `newArg`"),
newArg: String
) on FIELD
type MyType {
# ARGUMENT_DEFINITION (alternate example on a field's args)
fieldWithDeprecatedArgs(name: String! @deprecated): String
# FIELD_DEFINITION
deprecatedField: String @deprecated
}
enum MyEnum {
# ENUM_VALUE
OLD_VALUE @deprecated(reason: "Use `NEW_VALUE`.")
NEW_VALUE
}
input SomeInputType {
nonDeprecated: String
# INPUT_FIELD_DEFINITION
deprecated: String @deprecated
}
If @deprecated
appears elsewhere in a GraphQL document, it produces an error.
If you create a custom directive, you need to define it (and its valid locations) in your schema. You don't need to define default directives like
@deprecated
.
Schema directives vs. operation directives
Usually, a given directive appears exclusively in GraphQL schemas or exclusively in GraphQL operations (rarely both, although the spec allows this).
For example, among the default directives, @deprecated
is a schema-exclusive directive and @skip
and @include
are operation-exclusive directives.
The GraphQL spec lists all possible directive locations. Schema locations are listed under TypeSystemDirectiveLocation
, and operation locations are listed under ExecutableDirectiveLocation
.
Default directives
The GraphQL specification defines the following default directives:
Directive | Description |
---|---|
@deprecated(reason: String) | Marks the schema definition of a field or enum value as deprecated with an optional reason. |
@skip(if: Boolean!) | If true , the decorated field or fragment in an operation is not resolved by the GraphQL server. |
@include(if: Boolean!) | If false , the decorated field or fragment in an operation is not resolved by the GraphQL server. |