如何将两个 JSON 对象与 Rust 合并? [英] How can I merge two JSON objects with Rust?

问题描述

我有两个 JSON 文件:

I have two JSON files:

JSON 1

{
  "title": "This is a title",
  "person" : {
    "firstName" : "John",
    "lastName" : "Doe"
  },
  "cities":[ "london", "paris" ]
}

JSON 2

{
  "title": "This is another title",
  "person" : {
    "firstName" : "Jane"
  },
  "cities":[ "colombo" ]
}

我想将#2 合并到#1，其中#2 覆盖#1，产生以下输出:

I want to merge #2 into #1 where #2 overrides #1, producing following output:

{
  "title": "This is another title",
  "person" : {
    "firstName" : "Jane",
    "lastName" : "Doe"
  },
  "cities":[ "colombo" ]
}

我检查了箱子 json-patch 这样做但它不编译稳定锈.是否可以使用 serde_json 和稳定的 Rust 之类的东西做类似的事情?

I checked out the crate json-patch which does this but it does not compile against stable Rust. Is it possible to do something similar with something like serde_json and stable Rust?

推荐答案

将 Shepmaster 建议的答案放在下面

Placing the answer suggested by Shepmaster below

#[macro_use]
extern crate serde_json;

use serde_json::Value;

fn merge(a: &mut Value, b: Value) {
    match (a, b) {
        (a @ &mut Value::Object(_), Value::Object(b)) => {
            let a = a.as_object_mut().unwrap();
            for (k, v) in b {
                merge(a.entry(k).or_insert(Value::Null), v);
            }
        }
        (a, b) => *a = b,
    }
}

fn main() {
    let mut a = json!({
        "title": "This is a title",
        "person" : {
            "firstName" : "John",
            "lastName" : "Doe"
        },
        "cities":[ "london", "paris" ]
    });

    let b = json!({
        "title": "This is another title",
        "person" : {
            "firstName" : "Jane"
        },
        "cities":[ "colombo" ]
    });

    merge(&mut a, b);
    println!("{:#}", a);
}

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