Enum MaybeEmpty 

pub enum MaybeEmpty<T>
where
    T: Emptiable,
{
    Empty,
    Value(T),
}

A value that may be empty or not.

MaybeEmpty was introduced to help support the quirk described in Emptiable for Rust types which can’t represent the empty, additional value.

This type can be both serialized and deserialized. When serializing, MaybeEmpty::Empty will produce an empty value (0 bytes) for emptiable types. When deserializing, an empty value will be represented as MaybeEmpty::Empty.

Variants

Empty

Represents an empty value (0 bytes in the serialized form).

Value(T)

Represents a non-empty value.

Trait Implementations

impl<T> Clone for MaybeEmpty<T>

where T: Clone + Emptiable,

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

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> Debug for MaybeEmpty<T>

where T: Debug + Emptiable,

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

Formats the value using the given formatter.

impl<'frame, 'metadata, T> DeserializeValue<'frame, 'metadata> for MaybeEmpty<T>

where T: DeserializeValue<'frame, 'metadata> + Emptiable,

fn type_check(typ: &ColumnType<'_>) -> Result<(), TypeCheckError>

Checks that the column type matches what this type expects.

fn deserialize( typ: &'metadata ColumnType<'metadata>, v: Option<FrameSlice<'frame>>, ) -> Result<MaybeEmpty<T>, DeserializationError>

Deserialize a column value from given serialized representation.

impl<T> Hash for MaybeEmpty<T>

where T: Hash + Emptiable,

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

where __H: Hasher,

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> Ord for MaybeEmpty<T>

where T: Ord + Emptiable,

fn cmp(&self, other: &MaybeEmpty<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 for MaybeEmpty<T>

where T: PartialEq + Emptiable,

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

where T: PartialOrd + Emptiable,

fn partial_cmp(&self, other: &MaybeEmpty<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> SerializeValue for MaybeEmpty<T>

where T: SerializeValue + Emptiable,

fn serialize<'b>( &self, typ: &ColumnType<'_>, writer: CellWriter<'b>, ) -> Result<WrittenCellProof<'b>, SerializationError>

Serializes the value to given CQL type.

impl<T> Copy for MaybeEmpty<T>

where T: Copy + Emptiable,

impl<T> Eq for MaybeEmpty<T>

where T: Eq + Emptiable,

impl<T> StructuralPartialEq for MaybeEmpty<T>

where T: Emptiable,