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