Question

我想不出一种方法来将元素保存在HashMap中并同时进行编辑：

use std::collections::HashMap;

#[derive(Clone, Debug)]
pub struct Alliance {
    pub name: String,
    pub id: u32,
}

fn main() {
    let mut hashmap = HashMap::new();

    let mut alliance1 = Alliance {
        name: "alliance_1".to_string(),
        id: 1,
    };

    let mut alliance2 = Alliance {
        name: "alliance_2".to_string(),
        id: 2,
    };

    // Do I really need to clone the name strings here?
    let mut entry1 = hashmap.entry(alliance1.name.clone()).or_insert(alliance1);
    let mut entry2 = hashmap.entry(alliance2.name.clone()).or_insert(alliance2);

    swapNames(entry1, entry2);

    println!("{}", entry1.name);
    println!("{}", entry2.name);
}

fn swapNames(entry1: &mut Alliance, entry2: &mut Alliance) {
    let aux = entry1.name.clone();
    entry1.name = entry2.name.clone();
    entry2.name = aux;
}

playground

我得到一个我同意的错误：

error[E0499]: cannot borrow `hashmap` as mutable more than once at a time
  --> src/main.rs:24:22
   |
23 |     let mut entry1 = hashmap.entry(alliance1.name.clone()).or_insert(alliance1);
   |                      ------- first mutable borrow occurs here
24 |     let mut entry2 = hashmap.entry(alliance2.name.clone()).or_insert(alliance2);
   |                      ^^^^^^^ second mutable borrow occurs here
...
30 | }
   | - first borrow ends here

我只是不知道如何以编译方式进行编码。我需要保持Alliance结构可变，以便在代码中进一步对其进行编辑（swapNames函数只是一个示例）。

HashMap的问题，并且多次可变地借用

0 个答案: