Enum async_graphql::types::MaybeUndefined

pub enum MaybeUndefined<T> {
    Undefined,
    Null,
    Value(T),
}

Similar to Option, but it has three states, undefined, null and x.

Reference: https://spec.graphql.org/June2018/#sec-Null-Value

Examples

use async_graphql::*;

struct Query;

#[Object]
impl Query {
    async fn value1(&self, input: MaybeUndefined<i32>) -> i32 {
        if input.is_null() {
            1
        } else if input.is_undefined() {
            2
        } else {
            input.take().unwrap()
        }
    }
}

tokio::runtime::Runtime::new().unwrap().block_on(async {
    let schema = Schema::new(Query, EmptyMutation, EmptySubscription);
    let query = r#"
        {
            v1:value1(input: 99)
            v2:value1(input: null)
            v3:value1
        }"#;
    assert_eq!(
        schema.execute(query).await.into_result().unwrap().data,
        value!({
            "v1": 99,
            "v2": 1,
            "v3": 2,
        })
    );
});

Variants

Undefined

Null

Value

Tuple Fields of Value

0: T

Implementations

impl<T> MaybeUndefined<T>

pub fn is_undefined(&self) -> bool

Returns true if the MaybeUndefined is undefined.

pub fn is_null(&self) -> bool

Returns true if the MaybeUndefined is null.

pub fn is_value(&self) -> bool

Returns true if the MaybeUndefined is value.

pub fn value(&self) -> Option<&T>

Borrow the value, returns None if the value is undefined or null, otherwise returns Some(T).

pub fn take(self) -> Option<T>

Convert MaybeUndefined to Option.

Trait Implementations

impl<T: Clone> Clone for MaybeUndefined<T>

fn clone(&self) -> MaybeUndefined<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for MaybeUndefined<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for MaybeUndefined<T>

fn default() -> Self

Returns the “default value” for a type.

impl<'de, T> Deserialize<'de> for MaybeUndefined<T> where
    T: Deserialize<'de>, 

fn deserialize<D>(deserializer: D) -> Result<MaybeUndefined<T>, D::Error> where
    D: Deserializer<'de>, 

Deserialize this value from the given Serde deserializer.

impl<T> From<MaybeUndefined<T>> for Option<Option<T>>

fn from(maybe_undefined: MaybeUndefined<T>) -> Self

Performs the conversion.

impl<T: Hash> Hash for MaybeUndefined<T>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl<T: InputType> InputType for MaybeUndefined<T>

fn parse(value: Option<Value>) -> InputValueResult<Self>

Parse from Value. None represents undefined.

fn to_value(&self) -> Value

Convert to a Value for introspection.

impl<T: Ord> Ord for MaybeUndefined<T>

fn cmp(&self, other: &MaybeUndefined<T>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl<T: PartialEq> PartialEq<MaybeUndefined<T>> for MaybeUndefined<T>

fn eq(&self, other: &MaybeUndefined<T>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &MaybeUndefined<T>) -> bool

This method tests for !=.

impl<T: PartialOrd> PartialOrd<MaybeUndefined<T>> for MaybeUndefined<T>

fn partial_cmp(&self, other: &MaybeUndefined<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: Serialize> Serialize for MaybeUndefined<T>

fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error>

Serialize this value into the given Serde serializer.

impl<T: Type> Type for MaybeUndefined<T>

fn type_name() -> Cow<'static, str>

Type the name.

fn qualified_type_name() -> String

Qualified typename.

fn create_type_info(registry: &mut Registry) -> String

Create type information in the registry and return qualified typename.

fn introspection_type_name(&self) -> Cow<'static, str>

Introspection type name

impl<T: Copy> Copy for MaybeUndefined<T>

impl<T: Eq> Eq for MaybeUndefined<T>

impl<T> StructuralEq for MaybeUndefined<T>

impl<T> StructuralPartialEq for MaybeUndefined<T>