Enum Ttl 

pub enum Ttl {
    Missing,
    Forever,
    In(Duration),
}

What a key says about when it goes away.

Three answers rather than two, because a key that is not there and a key that is never going away are different things and code that confuses them deletes the wrong data. Redis says this with -2 and -1 and hopes you read the manual.

Variants

Missing

There is no such key.

Forever

The key is there and nothing is going to take it away.

In(Duration)

The key is there and this much of it is left.

Implementations

impl Ttl

pub fn left(self) -> Option<Duration>

How long is left, or None for a key that is missing or has no deadline.

The short answer for code that only wants to know whether it should refresh something. When the difference matters, match on the variants.

pub fn found(self) -> bool

Whether the key is there at all.

Trait Implementations

impl Clone for Ttl

fn clone(&self) -> Ttl

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Ttl

impl Debug for Ttl

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

Formats the value using the given formatter.

impl Eq for Ttl

impl PartialEq for Ttl

fn eq(&self, other: &Ttl) -> bool

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Ttl