Crate derive_enum_from_into
source ·Expand description
§Derive enum from try into
Implements From
and TryInto
for enums
use derive_enum_from_into::{EnumFrom, EnumTryInto};
use std::convert::TryInto;
#[derive(EnumFrom, EnumTryInto, PartialEq, Debug)]
enum Enum1 {
A(i32),
B,
}
assert_eq!(
Enum1::from(54i32),
Enum1::A(54i32)
);
let num: Result<i32, _> = Enum1::B.try_into();
assert!(num.is_err());
Ignores variants with duplicate type definitions or named fields
use derive_enum_from_into::{EnumFrom, EnumTryInto};
use std::convert::TryInto;
#[derive(EnumFrom, EnumTryInto, PartialEq, Debug)]
enum Enum1 {
A(String),
B(String),
C {
something: bool
},
}
// Results in compile errors
let enum1: Result<String, _> = Enum1::A("Hello".to_owned()).try_into();
let enum1: Result<bool, _> = (Enum1::C { something: true }).try_into();
From
can be ignored for variants with #[from_ignore]
TryInto
can also be implemented for references of the enum. Specific variants can be ignored with #[try_into_ignore]
use derive_enum_from_into::{EnumFrom, EnumTryInto};
use std::convert::TryInto;
#[derive(EnumTryInto, PartialEq, Debug)]
#[try_into_references(&, &mut, owned)]
enum NumberOrString {
Number(f32),
#[try_into_ignore]
String(String)
}
let x = NumberOrString::Number(4.);
assert_eq!(TryInto::<&f32>::try_into(&x), Ok(&4.));
// This won't compile as cannot TryInto String
// assert!(TryInto::<String>::try_into(NumberOrString::String("Hello World".to_owned())).is_err());
// `TryInto` comes in handy for `filter_map` cases
fn filter_only_f32s(iter: impl Iterator<Item=NumberOrString>) -> impl Iterator<Item=f32> {
iter.filter_map(|item| item.try_into().ok())
}
// `TryInto` returns `self` if it does not match
assert_eq!(TryInto::<f32>::try_into(NumberOrString::String("Hello World".to_owned())), Err(NumberOrString::String("Hello World".to_owned())));
Note that because of the default implementation of TryInto
the following will not compile. There are workarounds with wrapping X in a newtype pattern
#[derive(derive_enum_from_into::EnumTryInto)]
enum X {
Leaf(i32),
Nested(X)
}