#[non_exhaustive]pub enum Format {
Jpeg,
Png,
Unknown(UnknownVariantValue),
}
Expand description
When writing a match expression against Format
, 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 format = unimplemented!();
match format {
Format::Jpeg => { /* ... */ },
Format::Png => { /* ... */ },
other @ _ if other.as_str() == "NewFeature" => { /* handles a case for `NewFeature` */ },
_ => { /* ... */ },
}
The above code demonstrates that when format
represents
NewFeature
, the execution path will lead to the second last match arm,
even though the enum does not contain a variant Format::NewFeature
in the current version of SDK. The reason is that the variable other
,
created by the @
operator, is bound to
Format::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 Format::NewFeature
is defined.
Specifically, when format
represents NewFeature
,
the execution path will hit the second last match arm as before by virtue of
calling as_str
on Format::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
Jpeg
Png
Unknown(UnknownVariantValue)
Unknown
contains new variants that have been added since this code was generated.
Implementations§
Trait Implementations§
source§impl Ord for Format
impl Ord for Format
source§impl PartialEq<Format> for Format
impl PartialEq<Format> for Format
source§impl PartialOrd<Format> for Format
impl PartialOrd<Format> for Format
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 Format
impl StructuralEq for Format
impl StructuralPartialEq for Format
Auto Trait Implementations§
impl RefUnwindSafe for Format
impl Send for Format
impl Sync for Format
impl Unpin for Format
impl UnwindSafe for Format
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> Equivalent<K> for Qwhere
Q: Eq + ?Sized,
K: Borrow<Q> + ?Sized,
impl<Q, K> Equivalent<K> for Qwhere Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,
source§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
key
and return true
if they are equal.