Enum PreviousValue

pub enum PreviousValue {
    Any,
    MustExist,
    MustNotExist,
    MustExistAndMatch(Target),
    ExistingMustMatch(Target),
}

The desired value of an updated value

Variants

Any

No requirements are made towards the current value, and the new value is set unconditionally.

MustExist

The reference must exist and may have any value.

MustNotExist

Create the ref only, hence the reference must not exist.

MustExistAndMatch(Target)

The ref must exist and have the given value.

ExistingMustMatch(Target)

The ref may exist and have the given value, or may not exist at all.

Trait Implementations

impl Clone for PreviousValue

fn clone(&self) -> PreviousValue

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for PreviousValue

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

Formats the value using the given formatter.

impl Hash for PreviousValue

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 Ord for PreviousValue

fn cmp(&self, other: &PreviousValue) -> 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 PartialEq for PreviousValue

fn eq(&self, other: &PreviousValue) -> 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 PartialOrd for PreviousValue

fn partial_cmp(&self, other: &PreviousValue) -> 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 Eq for PreviousValue

impl StructuralPartialEq for PreviousValue