如何正确序列化/反序列化 rust？

Question

I have multiple structs that correspond to serialized/deserialized objects only known during runtime, example:

#[derive(Serialize, Deserialize)]
struct Car{
    model: i32,
    year: i32
}

#[derive(Serialize, Deserialize)]
struct Person{
    name: String,
    age: i32
}

Then I have functions to serialize and deserialize:

fn deserialize(data: Vec<u8>){
    let msg = str::from_utf8(data);
    serde_json::from_str(msg);
}

fn serialize(&self, object: Car) -> String{
    let msg = serde_json::to_string(&object).unwrap();
    return msg;
}

How can I make the deserialize function deserialize to both Car and Person (and possibly many other different types) and return the object? And how can I make the serialize function do the same thing: serialize Car, Person, and other objects (accepting these types in the attributes of the function)?

Answer 1

You can make deserialize generic over the Deserialize trait:

fn deserialize<'a, T: Deserialize<'a>>(data: &'a [u8]) -> T {
    let msg = str::from_utf8(data).unwrap();
    serde_json::from_str(msg).unwrap()
}

note that you need some lifetimes, because some types needs to borrow from the deserialized string, doc .

You can make serialize generic too:

fn serialize<T: Serialize>(object: &T) -> String {
    serde_json::to_string(object).unwrap()
}

playground

Answer 2

You want to use generic functions to allow different types to be passed in, and set trait bounds to make sure the objects are able to be serialized/deserialized. When calling serialize , the type will be inferred by the type of the parameter, but when calling deserialize , you need to use the turbofish ( ::<> ) to specify the type, if it can't be inferred.

use serde::{Serialize, Deserialize};
use std::str;

#[derive(Serialize, Deserialize)]
struct Car {
    model: i32,
    year: i32
}

#[derive(Serialize, Deserialize)]
struct Person {
    name: String,
    age: i32
}

// constrain output types to have the `Deserialize` trait
fn deserialize<'a, T>(data: &'a [u8]) -> T where T: Deserialize<'a> {
    let msg = str::from_utf8(data).unwrap();
    serde_json::from_str::<T>(msg).unwrap()
}

// shorthand for the above when `T` isn't needed in the function body
fn serialize(object: &impl Serialize) -> String {
    let msg = serde_json::to_string(object).unwrap();
    return msg;
}

fn main() {
    let car = Car { model: 7, year: 2077 };
    let person = Person { name: "Bob".to_string(), age: 42 };

    // types are infrerred from the parameters
    let car_json = serialize(&car);
    let person_json = serialize(&person);

    let _: Car = deserialize(car_json.as_bytes()); // output type can be inferred
    let _ = deserialize::<Car>(car_json.as_bytes()); // requres turbofish

    let _: Person = deserialize(person_json.as_bytes()); // works for `Person` too
}