有没有办法对结构的实例执行索引访问? [英] Is there a way to perform an index access to an instance of a struct?
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问题描述
有没有办法像这样对结构的实例执行索引访问:
Is there a way to perform an index access to an instance of a struct like this:
struct MyStruct {
// ...
}
impl MyStruct {
// ...
}
fn main() {
let s = MyStruct::new();
s["something"] = 533; // This is what I need
}
推荐答案
You can use the Index
and IndexMut
traits.
use std::ops::{Index, IndexMut};
struct Foo {
x: i32,
y: i32,
}
impl Index<&'_ str> for Foo {
type Output = i32;
fn index(&self, s: &str) -> &i32 {
match s {
"x" => &self.x,
"y" => &self.y,
_ => panic!("unknown field: {}", s),
}
}
}
impl IndexMut<&'_ str> for Foo {
fn index_mut(&mut self, s: &str) -> &mut i32 {
match s {
"x" => &mut self.x,
"y" => &mut self.y,
_ => panic!("unknown field: {}", s),
}
}
}
fn main() {
let mut foo = Foo { x: 0, y: 0 };
foo["y"] += 2;
println!("x: {}", foo["x"]);
println!("y: {}", foo["y"]);
}
它打印:
x: 0
y: 2
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