Enum aws_sdk_dynamodb::types::ReturnValue
source · #[non_exhaustive]pub enum ReturnValue {
AllNew,
AllOld,
None,
UpdatedNew,
UpdatedOld,
Unknown(UnknownVariantValue),
}
Expand description
When writing a match expression against ReturnValue
, 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 returnvalue = unimplemented!();
match returnvalue {
ReturnValue::AllNew => { /* ... */ },
ReturnValue::AllOld => { /* ... */ },
ReturnValue::None => { /* ... */ },
ReturnValue::UpdatedNew => { /* ... */ },
ReturnValue::UpdatedOld => { /* ... */ },
other @ _ if other.as_str() == "NewFeature" => { /* handles a case for `NewFeature` */ },
_ => { /* ... */ },
}
The above code demonstrates that when returnvalue
represents
NewFeature
, the execution path will lead to the second last match arm,
even though the enum does not contain a variant ReturnValue::NewFeature
in the current version of SDK. The reason is that the variable other
,
created by the @
operator, is bound to
ReturnValue::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 ReturnValue::NewFeature
is defined.
Specifically, when returnvalue
represents NewFeature
,
the execution path will hit the second last match arm as before by virtue of
calling as_str
on ReturnValue::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
AllNew
AllOld
None
UpdatedNew
UpdatedOld
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 ReturnValue
impl ReturnValue
source§impl ReturnValue
impl ReturnValue
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 ReturnValue
impl AsRef<str> for ReturnValue
source§impl Clone for ReturnValue
impl Clone for ReturnValue
source§fn clone(&self) -> ReturnValue
fn clone(&self) -> ReturnValue
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl Debug for ReturnValue
impl Debug for ReturnValue
source§impl Display for ReturnValue
impl Display for ReturnValue
source§impl From<&str> for ReturnValue
impl From<&str> for ReturnValue
source§impl FromStr for ReturnValue
impl FromStr for ReturnValue
source§impl Hash for ReturnValue
impl Hash for ReturnValue
source§impl Ord for ReturnValue
impl Ord for ReturnValue
source§fn cmp(&self, other: &ReturnValue) -> Ordering
fn cmp(&self, other: &ReturnValue) -> 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 ReturnValue
impl PartialEq for ReturnValue
source§fn eq(&self, other: &ReturnValue) -> bool
fn eq(&self, other: &ReturnValue) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl PartialOrd for ReturnValue
impl PartialOrd for ReturnValue
source§fn partial_cmp(&self, other: &ReturnValue) -> Option<Ordering>
fn partial_cmp(&self, other: &ReturnValue) -> 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 ReturnValue
impl StructuralPartialEq for ReturnValue
Auto Trait Implementations§
impl Freeze for ReturnValue
impl RefUnwindSafe for ReturnValue
impl Send for ReturnValue
impl Sync for ReturnValue
impl Unpin for ReturnValue
impl UnwindSafe for ReturnValue
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.