“key must be a string” when deserializing a JSON string with Serde

Question

I'm building a React app utilizing Rust for complex computations. In this case I'm passing a JSON formatted string from the React app to Rust:

{
  {'clientid': 1, 'category': 'Category #1', 'subcategory': 'Subcategory #1', 'cost': 1000.00},
  {'clientid': 1, 'category': 'Category #1', 'subcategory': 'Subcategory #2', 'cost': 2000.00}
}

I'm trying to figure out how to deserialze string In Rust into an array of structs defined as:

#[derive(Serialize, Deserialize, Debug)]
struct ClientBudget {
    clientid: u32,
    category: String,
    subcategory: String,
    cost: f32,
}

I tried:

let deserialized: ClientBudget = serde_json::from_str(&some_json).unwrap();

But this causes a panic:

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error("key must be a string"

How do I get Rust/serde to process this JSON string?

Answer 1

Your JSON is badly formatted. If you want a list, you must use [] not {} . You also need to deserialize a Vec of objects:

use serde::{Deserialize, Serialize}; // 1.0.114

#[derive(Serialize, Deserialize, Debug)]
struct ClientBudget {
    clientid: u32,
    category: String,
    subcategory: String,
    cost: f32,
}

fn main() {
    let data = r#"
[
    {"clientid": 1, "category": "Category #1", "subcategory": "Subcategory #1", "cost": 1000.00},
    {"clientid": 1, "category": "Category #1", "subcategory": "Subcategory #2", "cost": 2000.00}
]
    "#;
    let deserialized: Vec<ClientBudget> = serde_json::from_str(data).unwrap();

    println!("{:?}", deserialized);
}

Playground