Enum Optional

pub enum Optional<T> {
    Present(T),
    NotPresent,
    Null,
}

Represents a value that can either exist, not exist, or be null

This is a helper object for building Attributes. When including it in an attribute use #[serde(skip_serializing_if = "Optional::is_not_present", default)].

Variants

Present(T)

The key was present in the document and had a value

NotPresent

The key was not present

Null

The key was present and was null

Implementations

impl<T> Optional<T>

pub fn is_present(&self) -> bool

The key was present and had a value

pub fn is_not_present(&self) -> bool

The key was not present

pub fn is_null(&self) -> bool

The key was present and was null

pub fn map<U, F>(self, f: F) -> Optional<U>

where F: FnOnce(T) -> U,

Map the value if it was present

pub fn map_null<F>(self, f: F) -> Option<T>

where F: FnOnce() -> T,

Maps Present to Some, calls f is Null and maps the result to Some, maps NotPresent to None

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

Converts to Some if Present, otherwise converts to None

pub fn as_ref(&self) -> Optional<&T>

Converts from &Optional<T> to Optional<&T>

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

Converts from &mut Optional<T> to Optional<&mut T>

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

Unwraps an Optional, yeilding the content of a Present

Panics

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

pub fn unwrap(self) -> T

Move the value v out of the Optional<T> if it is Present(v).

Panics

Panics if the value is not a Present

pub fn unwrap_or_null(self, null: T) -> T

Unwraps if Present, returns null if Null

Panics

Panics if the value is NotPresent

pub fn unwrap_or_else_null<F>(self, null: F) -> T

where F: FnOnce() -> T,

Unwraps if Present, calls null and returns the result if Null

Panics

Panics if the value is NotPresent

Trait Implementations

impl<T: Clone> Clone for Optional<T>

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for Optional<T>

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

Formats the value using the given formatter.

impl<T> Default for Optional<T>

Defaults to NotPresent

fn default() -> Self

Returns the “default value” for a type.

impl<'de, T> Deserialize<'de> for Optional<T>

where T: DeserializeOwned,

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T> From<Option<T>> for Optional<T>

Maps None to NotPresent

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

Converts to this type from the input type.

impl<T: PartialEq> PartialEq for Optional<T>

fn eq(&self, other: &Optional<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> Serialize for Optional<T>

where T: Serialize,

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl<T: Eq> Eq for Optional<T>

impl<T> StructuralPartialEq for Optional<T>