#[non_exhaustive]pub enum FieldNamespace {
Custom,
System,
Unknown(UnknownVariantValue),
}
Expand description
When writing a match expression against FieldNamespace
, 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 fieldnamespace = unimplemented!();
match fieldnamespace {
FieldNamespace::Custom => { /* ... */ },
FieldNamespace::System => { /* ... */ },
other @ _ if other.as_str() == "NewFeature" => { /* handles a case for `NewFeature` */ },
_ => { /* ... */ },
}
The above code demonstrates that when fieldnamespace
represents
NewFeature
, the execution path will lead to the second last match arm,
even though the enum does not contain a variant FieldNamespace::NewFeature
in the current version of SDK. The reason is that the variable other
,
created by the @
operator, is bound to
FieldNamespace::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 FieldNamespace::NewFeature
is defined.
Specifically, when fieldnamespace
represents NewFeature
,
the execution path will hit the second last match arm as before by virtue of
calling as_str
on FieldNamespace::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
Custom
System
Unknown(UnknownVariantValue)
Unknown
contains new variants that have been added since this code was generated.
Implementations§
Trait Implementations§
source§impl AsRef<str> for FieldNamespace
impl AsRef<str> for FieldNamespace
source§impl Clone for FieldNamespace
impl Clone for FieldNamespace
source§fn clone(&self) -> FieldNamespace
fn clone(&self) -> FieldNamespace
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl Debug for FieldNamespace
impl Debug for FieldNamespace
source§impl From<&str> for FieldNamespace
impl From<&str> for FieldNamespace
source§impl FromStr for FieldNamespace
impl FromStr for FieldNamespace
source§impl Hash for FieldNamespace
impl Hash for FieldNamespace
source§impl Ord for FieldNamespace
impl Ord for FieldNamespace
source§fn cmp(&self, other: &FieldNamespace) -> Ordering
fn cmp(&self, other: &FieldNamespace) -> 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 FieldNamespace
impl PartialEq for FieldNamespace
source§fn eq(&self, other: &FieldNamespace) -> bool
fn eq(&self, other: &FieldNamespace) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl PartialOrd for FieldNamespace
impl PartialOrd for FieldNamespace
source§fn partial_cmp(&self, other: &FieldNamespace) -> Option<Ordering>
fn partial_cmp(&self, other: &FieldNamespace) -> 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 FieldNamespace
impl StructuralEq for FieldNamespace
impl StructuralPartialEq for FieldNamespace
Auto Trait Implementations§
impl RefUnwindSafe for FieldNamespace
impl Send for FieldNamespace
impl Sync for FieldNamespace
impl Unpin for FieldNamespace
impl UnwindSafe for FieldNamespace
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
§impl<Q, K> Comparable<K> for Q
impl<Q, K> Comparable<K> for Q
§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
key
and return true
if they are equal.