Enum aws_sdk_s3::types::MetadataDirective
source · #[non_exhaustive]pub enum MetadataDirective {
Copy,
Replace,
Unknown(UnknownVariantValue),
}
Expand description
When writing a match expression against MetadataDirective
, 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 metadatadirective = unimplemented!();
match metadatadirective {
MetadataDirective::Copy => { /* ... */ },
MetadataDirective::Replace => { /* ... */ },
other @ _ if other.as_str() == "NewFeature" => { /* handles a case for `NewFeature` */ },
_ => { /* ... */ },
}
The above code demonstrates that when metadatadirective
represents
NewFeature
, the execution path will lead to the second last match arm,
even though the enum does not contain a variant MetadataDirective::NewFeature
in the current version of SDK. The reason is that the variable other
,
created by the @
operator, is bound to
MetadataDirective::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 MetadataDirective::NewFeature
is defined.
Specifically, when metadatadirective
represents NewFeature
,
the execution path will hit the second last match arm as before by virtue of
calling as_str
on MetadataDirective::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
Copy
Replace
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 MetadataDirective
impl MetadataDirective
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 MetadataDirective
impl AsRef<str> for MetadataDirective
source§impl Clone for MetadataDirective
impl Clone for MetadataDirective
source§fn clone(&self) -> MetadataDirective
fn clone(&self) -> MetadataDirective
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl Debug for MetadataDirective
impl Debug for MetadataDirective
source§impl Display for MetadataDirective
impl Display for MetadataDirective
source§impl From<&str> for MetadataDirective
impl From<&str> for MetadataDirective
source§impl FromStr for MetadataDirective
impl FromStr for MetadataDirective
source§impl Hash for MetadataDirective
impl Hash for MetadataDirective
source§impl Ord for MetadataDirective
impl Ord for MetadataDirective
source§fn cmp(&self, other: &MetadataDirective) -> Ordering
fn cmp(&self, other: &MetadataDirective) -> 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 MetadataDirective
impl PartialEq for MetadataDirective
source§impl PartialOrd for MetadataDirective
impl PartialOrd for MetadataDirective
impl Eq for MetadataDirective
impl StructuralPartialEq for MetadataDirective
Auto Trait Implementations§
impl Freeze for MetadataDirective
impl RefUnwindSafe for MetadataDirective
impl Send for MetadataDirective
impl Sync for MetadataDirective
impl Unpin for MetadataDirective
impl UnwindSafe for MetadataDirective
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<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
source§default unsafe fn clone_to_uninit(&self, dst: *mut T)
default unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)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.