Enum 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/October2021/#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()
        }
    }
}

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(T)

Implementations

impl<T> MaybeUndefined<T>

pub const fn is_undefined(&self) -> bool

Returns true if the MaybeUndefined<T> is undefined.

pub const fn is_null(&self) -> bool

Returns true if the MaybeUndefined<T> is null.

pub const fn is_value(&self) -> bool

Returns true if the MaybeUndefined<T> contains value.

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

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

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

Converts the MaybeUndefined<T> to Option<T>.

pub const fn as_opt_ref(&self) -> Option<Option<&T>>

Converts the MaybeUndefined<T> to Option<Option<T>>.

pub fn as_opt_deref<U>(&self) -> Option<Option<&U>>

where U: ?Sized, T: Deref<Target = U>,

Converts the MaybeUndefined<T> to Option<Option<&U>>.

pub fn contains_value<U>(&self, x: &U) -> bool

where U: PartialEq<T>,

Returns true if the MaybeUndefined<T> contains the given value.

pub fn contains<U>(&self, x: &Option<U>) -> bool

where U: PartialEq<T>,

Returns true if the MaybeUndefined<T> contains the given nullable value.

pub fn map<U, F: FnOnce(Option<T>) -> Option<U>>( self, f: F, ) -> MaybeUndefined<U>

Maps a MaybeUndefined<T> to MaybeUndefined<U> by applying a function to the contained nullable value

pub fn map_value<U, F: FnOnce(T) -> U>(self, f: F) -> MaybeUndefined<U>

Maps a MaybeUndefined<T> to MaybeUndefined<U> by applying a function to the contained value

pub fn update_to(self, value: &mut Option<T>)

Update value if the MaybeUndefined<T> is not undefined.

Example

use async_graphql::MaybeUndefined;

let mut value = None;

MaybeUndefined::Value(10i32).update_to(&mut value);
assert_eq!(value, Some(10));

MaybeUndefined::Undefined.update_to(&mut value);
assert_eq!(value, Some(10));

MaybeUndefined::Null.update_to(&mut value);
assert_eq!(value, None);

impl<T, E> MaybeUndefined<Result<T, E>>

pub fn transpose(self) -> Result<MaybeUndefined<T>, E>

Transposes a MaybeUndefined of a Result into a Result of a MaybeUndefined.

MaybeUndefined::Undefined will be mapped to Ok(MaybeUndefined::Undefined). MaybeUndefined::Null will be mapped to Ok(MaybeUndefined::Null). MaybeUndefined::Value(Ok(_)) and MaybeUndefined::Value(Err(_)) will be mapped to Ok(MaybeUndefined::Value(_)) and Err(_).

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

Converts to this type from the input type.

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

fn from(value: Option<Option<T>>) -> Self

Converts to this type from the input type.

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, Self: Sized,

Feeds a slice of this type into the given Hasher.

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

type RawValueType = <T as InputType>::RawValueType

The raw type used for validator.

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

Parse from Value. None represents undefined.

fn to_value(&self) -> Value

Convert to a Value for introspection.

fn as_raw_value(&self) -> Option<&Self::RawValueType>

Returns a reference to the raw value.

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

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

where Self: Sized,

Restrict a value to a certain interval.

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

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: PartialOrd> PartialOrd 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

Tests less than (for self and other) and is used by the < operator.

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

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

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

Tests greater than (for self and other) and is used by the > operator.

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

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: Copy> Copy for MaybeUndefined<T>

impl<T: Eq> Eq for MaybeUndefined<T>

impl<T> StructuralPartialEq for MaybeUndefined<T>