Enum Nullable 

pub enum Nullable<T> {
    ImplicitNull,
    ExplicitNull,
    Some(T),
}

Nullable can be used in situations where you need to distinguish between an implicitly and explicitly null input value.

The GraphQL spec states that these two field calls are similar, but are not identical:

{
  field(arg: null)
  field
}

The first has explicitly provided null to the argument “arg”, while the second has implicitly not provided a value to the argument “arg”. These two forms may be interpreted differently. For example, a mutation representing deleting a field vs not altering a field, respectively.

In cases where you do not need to be able to distinguish between the two types of null, you should simply use Option<T>.

Variants

ImplicitNull

No value

ExplicitNull

No value, explicitly specified to be null

Some(T)

Some value T

Implementations

impl<T> Nullable<T>

pub fn is_explicit_null(&self) -> bool

Returns true if the nullable is a ExplicitNull value.

pub fn is_implicit_null(&self) -> bool

Returns true if the nullable is a ImplicitNull value.

pub fn is_some(&self) -> bool

Returns true if the nullable is a Some value.

pub fn is_null(&self) -> bool

Returns true if the nullable is not a Some value.

pub fn as_mut(&mut self) -> Nullable<&mut T>

Converts from &mut Nullable<T> to Nullable<&mut T>.

pub fn expect(self, msg: &str) -> T

Returns the contained Some value, consuming the self value.

Panics

Panics if the value is not a Some with a custom panic message provided by msg.

pub fn unwrap_or(self, default: T) -> T

Returns the contained Some value or a provided default.

pub fn unwrap_or_else<F: FnOnce() -> T>(self, f: F) -> T

Returns the contained Some value or computes it from a closure.

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

Maps a Nullable<T> to Nullable<U> by applying a function to a contained value.

pub fn map_or<U, F: FnOnce(T) -> U>(self, default: U, f: F) -> U

Applies a function to the contained value (if any), or returns the provided default (if not).

pub fn map_or_else<U, D: FnOnce() -> U, F: FnOnce(T) -> U>( self, default: D, f: F, ) -> U

Applies a function to the contained value (if any), or computes a default (if not).

pub fn ok_or<E>(self, err: E) -> Result<T, E>

Transforms the Nullable<T> into a Result<T, E>, mapping Some(v) to Ok(v) and ImplicitNull or ExplicitNull to Err(err).

pub fn ok_or_else<E, F: FnOnce() -> E>(self, err: F) -> Result<T, E>

Transforms the Nullable<T> into a Result<T, E>, mapping Some(v) to Ok(v) and ImplicitNull or ExplicitNull to Err(err()).

pub fn or(self, b: Self) -> Self

Returns the nullable if it contains a value, otherwise returns b.

pub fn or_else<F: FnOnce() -> Nullable<T>>(self, f: F) -> Nullable<T>

Returns the nullable if it contains a value, otherwise calls f and returns the result.

pub fn replace(&mut self, value: T) -> Self

Replaces the actual value in the nullable by the value given in parameter, returning the old value if present, leaving a Some in its place without deinitializing either one.

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

Converts from Nullable<T> to Option<T>.

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

Converts from Nullable<T> to Option<Option<T>>, mapping Some(v) to Some(Some(v)), ExplicitNull to Some(None), and ImplicitNull to None.

impl<T: Copy> Nullable<&T>

pub fn copied(self) -> Nullable<T>

Maps a Nullable<&T> to a Nullable<T> by copying the contents of the nullable.

impl<T: Copy> Nullable<&mut T>

pub fn copied(self) -> Nullable<T>

Maps a Nullable<&mut T> to a Nullable<T> by copying the contents of the nullable.

impl<T: Clone> Nullable<&T>

pub fn cloned(self) -> Nullable<T>

Maps a Nullable<&T> to a Nullable<T> by cloning the contents of the nullable.

impl<T: Clone> Nullable<&mut T>

pub fn cloned(self) -> Nullable<T>

Maps a Nullable<&mut T> to a Nullable<T> by cloning the contents of the nullable.

Trait Implementations

impl<T: Clone> Clone for Nullable<T>

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

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for Nullable<T>

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

Formats the value using the given formatter.

impl<T> Default for Nullable<T>

fn default() -> Self

Returns the “default value” for a type.

impl<S, T: FromInputValue<S>> FromInputValue<S> for Nullable<T>

type Error = <T as FromInputValue<S>>::Error

Type of this conversion error.

fn from_input_value(v: &InputValue<S>) -> Result<Self, Self::Error>

Performs the conversion.

fn from_implicit_null() -> Result<Self, Self::Error>

Performs the conversion from an absent value (e.g. to distinguish between implicit and explicit null).

impl<S, T> GraphQLType<S> for Nullable<T>

where T: GraphQLType<S>, S: ScalarValue,

fn name(_: &Self::TypeInfo) -> Option<ArcStr>

Returns name of this GraphQLType to expose.

fn meta(info: &Self::TypeInfo, registry: &mut Registry<S>) -> MetaType<S>

Returns MetaType representing this GraphQLType.

impl<S, T> GraphQLValue<S> for Nullable<T>

where S: ScalarValue, T: GraphQLValue<S>,

type Context = <T as GraphQLValue<S>>::Context

Context type for this GraphQLValue.

type TypeInfo = <T as GraphQLValue<S>>::TypeInfo

Type that may carry additional schema information for this GraphQLValue.

fn type_name(&self, _: &Self::TypeInfo) -> Option<ArcStr>

Returns name of the GraphQLType exposed by this GraphQLValue.

fn resolve( &self, info: &Self::TypeInfo, _: Option<&[Selection<'_, S>]>, executor: &Executor<'_, '_, Self::Context, S>, ) -> ExecutionResult<S>

Resolves the provided selection_set against this GraphQLValue.

fn resolve_field( &self, _info: &Self::TypeInfo, _field_name: &str, _arguments: &Arguments<'_, S>, _executor: &Executor<'_, '_, Self::Context, S>, ) -> ExecutionResult<S>

Resolves the value of a single field on this GraphQLValue.

fn resolve_into_type( &self, info: &Self::TypeInfo, type_name: &str, selection_set: Option<&[Selection<'_, S>]>, executor: &Executor<'_, '_, Self::Context, S>, ) -> ExecutionResult<S>

Resolves this GraphQLValue (being an interface or an union) into a concrete downstream object type.

fn concrete_type_name( &self, context: &Self::Context, info: &Self::TypeInfo, ) -> String

Returns the concrete GraphQLType name for this GraphQLValue being an interface, an union or an object.

impl<S, T> GraphQLValueAsync<S> for Nullable<T>

where T: GraphQLValueAsync<S>, T::TypeInfo: Sync, T::Context: Sync, S: ScalarValue + Send + Sync,

fn resolve_async<'a>( &'a self, info: &'a Self::TypeInfo, _: Option<&'a [Selection<'_, S>]>, executor: &'a Executor<'_, '_, Self::Context, S>, ) -> BoxFuture<'a, ExecutionResult<S>>

Resolves the provided selection_set against this GraphQLValueAsync.

fn resolve_field_async<'a>( &'a self, _info: &'a Self::TypeInfo, _field_name: &'a str, _arguments: &'a Arguments<'_, S>, _executor: &'a Executor<'_, '_, Self::Context, S>, ) -> BoxFuture<'a, ExecutionResult<S>>

Resolves the value of a single field on this GraphQLValueAsync.

fn resolve_into_type_async<'a>( &'a self, info: &'a Self::TypeInfo, type_name: &str, selection_set: Option<&'a [Selection<'a, S>]>, executor: &'a Executor<'a, 'a, Self::Context, S>, ) -> BoxFuture<'a, ExecutionResult<S>>

Resolves this GraphQLValueAsync (being an interface or an union) into a concrete downstream object type.

impl<T: Hash> Hash for Nullable<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<S, T> IsInputType<S> for Nullable<T>

where T: IsInputType<S>, S: ScalarValue,

fn mark()

An arbitrary function without meaning.

impl<T: Ord> Ord for Nullable<T>

fn cmp(&self, other: &Nullable<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 Nullable<T>

fn eq(&self, other: &Nullable<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 Nullable<T>

fn partial_cmp(&self, other: &Nullable<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<S, T> ToInputValue<S> for Nullable<T>

where T: ToInputValue<S>,

fn to_input_value(&self) -> InputValue<S>

Performs the conversion.

impl<T: Copy> Copy for Nullable<T>

impl<T: Eq> Eq for Nullable<T>

impl<T> StructuralPartialEq for Nullable<T>