1 unstable release
0.5.0 | Apr 19, 2019 |
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#34 in #attribute
Used in tyenum
8KB
158 lines
Attribute macro for less verbose creation of enums having different types as variants.
Also automatically implements From
, TryFrom
and fn is<T>() -> bool
to check if its inner item is of type T
and is able to give you trait objects depending on which arguments you specify.
Basic Usage:
use tyenum::tyenum;
struct A;
struct B;
struct C;
#[tyenum]
enum Test {
A,
BB(B),
C(C),
}
results in:
enum Test {
A(A),
BB(B),
C(C),
}
and allows for:
assert_eq!(Test::A(A), A.into());
assert!(Test::A(A).is::<A>());
assert_eq!(Test::A(A).try_into(), Ok(A));
Arguments
tyenum
also takes 2 optional arguments:
derive
#[tyenum(derive=[Display])]
enum Test {
A,
BB(B),
}
trait Name {
fn name(&self) -> String;
}
impl Name for A {
fn name(&self) -> String {
String::from("A")
}
}
impl Name for B {
fn name(&self) -> String {
String::from("B")
}
}
This implements std::ops::Deref
and std::ops::DerefMut
to a trait object of the derived trait for the enum, which allows you to easily call trait methods, which will be redirected to the variant:
assert_eq!("A", Test::A(A).name());
trait_obj
Requires nightly and #![feature(specialization)] and pollutes your namespace, a trait named "ToTraitObject" will be generated!
#[tyenum(trait_obj=[Name])]
enum Test {
A,
BB(B),
}
trait Name {
fn name(&self) -> String;
}
impl Name for A {
fn name(&self) -> String {
String::from("A")
}
}
allows you to do this:
fn try_print_name(test: Test) {
if let Some(named) = test.trait_obj() {
println!("{}",named.name());
}
}
Dependencies
~2MB
~46K SLoC