[英]How do I convert an enum reference to a number?
I have an enum: 我有一个枚举:
enum Foo {
Bar = 1,
}
How do I convert a reference to this enum into an integer to be used in math? 如何将对此枚举的引用转换为要在数学中使用的整数?
fn f(foo: &Foo) {
let f = foo as u8; // error[E0606]: casting `&Foo` as `u8` is invalid
let f = foo as &u8; // error[E0605]: non-primitive cast: `&Foo` as `&u8`
let f = *foo as u8; // error[E0507]: cannot move out of borrowed content
}
*foo as u8
is correct, but you have to implement Copy
because otherwise you would leave behind an invalid reference. *foo as u8
是正确的,但你必须实现Copy
,否则你会留下无效的引用。
#[derive(Copy, Clone)]
enum Foo {
Bar = 1,
}
fn f(foo: &Foo) -> u8 {
*foo as u8
}
Since your enum will be a very lightweight object you should pass it around by value anyway, for which you would need Copy
as well. 由于你的枚举将是一个非常轻量级的对象,你应该按值传递它,你也需要Copy
它。
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