Enum aws_sdk_wafv2::types::FallbackBehavior
source · #[non_exhaustive]pub enum FallbackBehavior {
Match,
NoMatch,
Unknown(UnknownVariantValue),
}
Expand description
When writing a match expression against FallbackBehavior
, it is important to ensure
your code is forward-compatible. That is, if a match arm handles a case for a
feature that is supported by the service but has not been represented as an enum
variant in a current version of SDK, your code should continue to work when you
upgrade SDK to a future version in which the enum does include a variant for that
feature.
Here is an example of how you can make a match expression forward-compatible:
# let fallbackbehavior = unimplemented!();
match fallbackbehavior {
FallbackBehavior::Match => { /* ... */ },
FallbackBehavior::NoMatch => { /* ... */ },
other @ _ if other.as_str() == "NewFeature" => { /* handles a case for `NewFeature` */ },
_ => { /* ... */ },
}
The above code demonstrates that when fallbackbehavior
represents
NewFeature
, the execution path will lead to the second last match arm,
even though the enum does not contain a variant FallbackBehavior::NewFeature
in the current version of SDK. The reason is that the variable other
,
created by the @
operator, is bound to
FallbackBehavior::Unknown(UnknownVariantValue("NewFeature".to_owned()))
and calling as_str
on it yields "NewFeature"
.
This match expression is forward-compatible when executed with a newer
version of SDK where the variant FallbackBehavior::NewFeature
is defined.
Specifically, when fallbackbehavior
represents NewFeature
,
the execution path will hit the second last match arm as before by virtue of
calling as_str
on FallbackBehavior::NewFeature
also yielding "NewFeature"
.
Explicitly matching on the Unknown
variant should
be avoided for two reasons:
- The inner data
UnknownVariantValue
is opaque, and no further information can be extracted. - It might inadvertently shadow other intended match arms.
Variants (Non-exhaustive)§
This enum is marked as non-exhaustive
Match
NoMatch
Unknown(UnknownVariantValue)
Unknown
. See the docs on this enum for the correct way to handle unknown variants.Unknown
contains new variants that have been added since this code was generated.
Implementations§
source§impl FallbackBehavior
impl FallbackBehavior
sourcepub fn try_parse(value: &str) -> Result<Self, UnknownVariantError>
pub fn try_parse(value: &str) -> Result<Self, UnknownVariantError>
Parses the enum value while disallowing unknown variants.
Unknown variants will result in an error.
Trait Implementations§
source§impl AsRef<str> for FallbackBehavior
impl AsRef<str> for FallbackBehavior
source§impl Clone for FallbackBehavior
impl Clone for FallbackBehavior
source§fn clone(&self) -> FallbackBehavior
fn clone(&self) -> FallbackBehavior
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl Debug for FallbackBehavior
impl Debug for FallbackBehavior
source§impl Display for FallbackBehavior
impl Display for FallbackBehavior
source§impl From<&str> for FallbackBehavior
impl From<&str> for FallbackBehavior
source§impl FromStr for FallbackBehavior
impl FromStr for FallbackBehavior
source§impl Hash for FallbackBehavior
impl Hash for FallbackBehavior
source§impl Ord for FallbackBehavior
impl Ord for FallbackBehavior
source§fn cmp(&self, other: &FallbackBehavior) -> Ordering
fn cmp(&self, other: &FallbackBehavior) -> Ordering
1.21.0 · source§fn max(self, other: Self) -> Selfwhere
Self: Sized,
fn max(self, other: Self) -> Selfwhere
Self: Sized,
source§impl PartialEq for FallbackBehavior
impl PartialEq for FallbackBehavior
source§fn eq(&self, other: &FallbackBehavior) -> bool
fn eq(&self, other: &FallbackBehavior) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl PartialOrd for FallbackBehavior
impl PartialOrd for FallbackBehavior
source§fn partial_cmp(&self, other: &FallbackBehavior) -> Option<Ordering>
fn partial_cmp(&self, other: &FallbackBehavior) -> Option<Ordering>
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
self
and other
) and is used by the <=
operator. Read moreimpl Eq for FallbackBehavior
impl StructuralPartialEq for FallbackBehavior
Auto Trait Implementations§
impl Freeze for FallbackBehavior
impl RefUnwindSafe for FallbackBehavior
impl Send for FallbackBehavior
impl Sync for FallbackBehavior
impl Unpin for FallbackBehavior
impl UnwindSafe for FallbackBehavior
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<Q, K> Comparable<K> for Q
impl<Q, K> Comparable<K> for Q
source§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
source§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
source§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
key
and return true
if they are equal.