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Popeye's questions

Martin Hope
Popeye
Asked: 2025-02-08 07:25:18 +0800 CST
  • 2

我正在尝试生成如下所示的 json 对象

// final json output expected
{
    "j1": {
        "1981": {
            "income": 215
        },
        "1982": {
            "income": 350
        },
    },
    "j2": {
        "1981": {
            "income": 100
        },
        "1982": {
            "income": 215
        },
    }
}

我有以下代码

use serde_json::{Value, Map};

struct s {
    name: String,
    year: i32,
    income: i64
}

fn main() {
    let rows :Vec<s> = vec!(
        s { name: "j1".to_string(), year: 1981, income: 100},
        s { name: "j1".to_string(), year: 1981, income: 115},
        s { name: "j1".to_string(), year: 1982, income: 120},
        s { name: "j1".to_string(), year: 1982, income: 100},
        s { name: "j1".to_string(), year: 1982, income: 130},
        s { name: "j2".to_string(), year: 1981, income: 100},
        s { name: "j2".to_string(), year: 1982, income: 120},
        s { name: "j2".to_string(), year: 1982, income: 130}
    );
    
    let mut data_map: Map<String, Value> = Map::new();
    for row in rows {
        let  mut name: &Map<String, Value> = match data_map.get(&row.name) {
            Some(val) => { &val.as_object().unwrap() },
            None => { &Map::new() }
        };
        let mut year:  &Map<String, Value> = match data_map.get(&row.year.to_string()) {
            Some(val) => { &val.as_object().unwrap() },
            None => { &Map::new() }
        };
        let income: i64 = year.get("income").unwrap_or(&Value::Number(0i64.into())).as_i64().unwrap() + row.income;
        year.insert("income".to_string(), Value::Number(income.into()));
    }
}

我创建了这个代码来提问。我还咨询了 deepseek 等

我收到的错误消息是

error[E0596]: cannot borrow `*year` as mutable, as it is behind a `&` reference
  --> src\main.rs:32:9
   |
32 |         year.insert("income".to_string(), Value::Number(income.into()));
   |         ^^^^ `year` is a `&` reference, so the data it refers to cannot be borrowed as mutable
   |
help: consider changing this binding's type
   |
27 |         let mut year: &mut serde_json::Map<std::string::String, Value> = match data_map.get(&row.year.to_string()) {
   |                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

显然我对引用和借用理解不足。如能得到任何帮助我将不胜感激。

rust