如何从 Rust 中的 Vec 中提取两个可变元素 [英] How do I extract two mutable elements from a Vec in rust
问题描述
我正在尝试从 Vec 中提取两个元素,它始终至少包含两个元素.这两个元素需要可变地提取,因为我需要能够在单个操作中更改它们的值.
I'm trying to extract two elements from a Vec, which will always contain at least two elements. These two elements need to be extracted mutably as I need to be able to change values on both as part of a single operation.
示例代码:
struct Piece {
x: u32,
y: u32,
name: &'static str
}
impl Piece {
fn exec(&self, target: &mut Piece) {
println!("{} -> {}", self.name, target.name)
}
}
struct Board {
pieces: Vec<Piece>
}
fn main() {
let mut board = Board {
pieces: vec![
Piece{ x: 0, y: 0, name: "A" },
Piece{ x: 1, y: 1, name: "B" }
]
};
let mut a = board.pieces.get_mut(0);
let mut b = board.pieces.get_mut(1);
a.exec(b);
}
目前,这无法通过以下编译器错误构建:
At present, this fails to build with the following compiler errors:
piece.rs:26:17: 26:29 error: cannot borrow `board.pieces` as mutable more than once at a time
piece.rs:26 let mut b = board.pieces.get_mut(1);
^~~~~~~~~~~~
piece.rs:25:17: 25:29 note: previous borrow of `board.pieces` occurs here; the mutable borrow prevents subsequent moves, borrows, or modification of `board.pieces` until the borrow ends
piece.rs:25 let mut a = board.pieces.get_mut(0);
^~~~~~~~~~~~
piece.rs:28:2: 28:2 note: previous borrow ends here
piece.rs:17 fn main() {
...
piece.rs:28 }
不幸的是,我需要能够获得对两者的可变引用,以便我可以在 Piece.exec 方法中修改两者.有什么想法,还是我试图以错误的方式做到这一点?
Unfortunately, I need to be able to obtain a mutable reference to both so that I can modify both within the Piece.exec method. Any ideas, or am I trying to do this the wrong way?
推荐答案
Rust 不能在编译时保证 get_mut
不会可变地借用同一个元素两次,所以 get_mut
可变地借用整个向量.
Rust can't guarantee at compile time that get_mut
is not going to mutably borrow the same element twice, so get_mut
borrows the entire vector mutably.
改为使用切片
pieces.as_slice().split_at_mut(1)
是你想在这里使用的.
pieces.as_slice().split_at_mut(1)
is what you want to use here.
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