如何修改从成员函数调用的闭包中的self？
我试图计算合法的棋步，并且遇到了满足借用检查器的问题。 我有一个结构Chess实现这些方法（非重要的代码替换... ）：
// internal iterator over (possibly not legal) moves
fn get_moves<F>(&self, func: F)
where
F: Fn(/* ... */),
{
func(/* ... */); // move 1
func(/* ... */); // move 2
func(/* ... */); // etc...
}
fn is_legal_move(&mut self) -> bool {
// notice this takes a mutable self. For performance
// reasons, the move is made, legality is checked, then I
// undo the move, so it must be mutable to be able to move pieces
make_move(/* ... */);
// check if legal
undo_move(/* ... */);
//return true if legal
}
fn get_legal_moves(&self) /* -> ... */ {
self.get_moves(|/* ... */| {
if self.is_legal_move(/* ... */) { // <-- error here
// do something with legal move
}
})
}
我在get_legal_moves得到了一个编译错误，因为我正在修改关闭内部的self ，而'get_moves'仍在借用self 。
我创建了一个简化的示例，显示我正在尝试解决的问题：
struct Tester {
x: i8,
}
impl Tester {
fn traverse<Func>(&mut self, mut f: Func)
where
Func: FnMut(),
{
//in real-world, this would probably iterate over something
f();
}
}
fn main() {
let mut tester = Tester { x: 8 };
tester.traverse(|| {
tester.x += 1; //I want to be able to modify tester here
});
println!("{}", tester.x);
}
操场
错误：
error[E0499]: cannot borrow `tester` as mutable more than once at a time
--> src/main.rs:17:21
|
17 | tester.traverse(|| {
| ------ ^^ second mutable borrow occurs here
| |
| first mutable borrow occurs here
18 | tester.x += 1; //I want to be able to modify tester here
| ------ borrow occurs due to use of `tester` in closure
19 | });
| - first borrow ends here
我怎样才能满足借用检查器，以便代码可以编译？
您可以做的最简单的更改是将引用传递给闭包：
struct Tester {
x: i8,
}
impl Tester {
fn traverse<F>(&mut self, mut f: F)
where
F: FnMut(&mut Tester),
{
f(self);
}
}
fn main() {
let mut tester = Tester { x: 8 };
tester.traverse(|z| z.x += 1);
println!("{}", tester.x);
}
这可以防止在Rust中不允许使用多个可变引用（也称为别名）。
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