In Rust, how can a JSON be deserialized in multiple structs?

May 26, 2023

Lets’ say we have the following JSON:

{
   name:"John",
   age:"30"
}

and the two following structs:

struct Name {
   name: String;
}

struct Age {
   age: i32
}

What would be an efficient way to deserialize this JSON into this structs?

>Solution :

Create a third struct containing each of the others and use #[serde(flatten)] to deserialize each field as if it’s a single flat struct:

use serde::Deserialize;

#[derive(Debug, Deserialize)]
struct Name {
    name: String,
}
#[derive(Debug, Deserialize)]
struct Age {
    age: i32,
}
#[derive(Debug, Deserialize)]
struct Person {
    #[serde(flatten)]
    name: Name,
    #[serde(flatten)]
    age: Age,
}

fn main() {
    dbg!(serde_json::from_str::<Person>(r#"{ "name": "John", "age": 30 }"#).unwrap());
    // Person {
    //     name: Name {
    //         name: "John",
    //     },
    //     age: Age {
    //         age: 30,
    //     },
    // }
}

playground