deserializing serde_json from API in rust

Question

I am attempting to scrape the JSON from this endpoint https://prices.runescape.wiki/api/v1/osrs/latest .

#[derive(Serialize, Deserialize, Debug)]
struct Latest {
    high: u32,
    highTime: String,
    low: String,
    lowTime: String,
}

#[derive(Serialize, Deserialize, Debug)]
struct Data {
    #[serde(with = "serde_with::json::nested")]
    data: Vec<Latest>,
}

#[derive(Serialize, Deserialize, Debug)]
struct Datav2 {
    #[serde(with = "serde_with::json::nested")]
    data: HashMap<u32, Vec<Latest>>,
}
#[cfg(not(target_arch = "wasm32"))]
#[tokio::main]
async fn main() -> Result<(), reqwest::Error> {

     let res = reqwest::get(url).await?;
    let response = &res.json::<Datav2>().await?;

}

I've tried two versions of the datastructure. Data is using a vector of latest, but i noticed each object has a unique ID, so in DataV2 i tried using a hashmap but i get the same error. I've also tried unnested versions without using Serde_with.

I get the error Error: reqwest::Error { kind: Decode, source: Error("invalid type: map, expected valid json object", line: 1, column: 8)

It seems my datastructure is messed up, but have been trying for hours to figure out the correct data structure to use.

Answer 1

There are multiple issues with your current code.

1. Datav2 is closer, but still not correct. It is not a HashMap<u32, Vec<Latest>> but a HashMap<u32, Latest> . There is no need to have another Vec , since each number is assigned a value in the JSON.
2. highTime , low , lowTime are not of type String (since they have no quotes in the JSON), but are unsigned numbers (to be on the safe side I just assumed them to be u64 ).
3. Apparently the fields of Latest can be null , so they need to be Option s.
4. I would still use snake_case for the field names in the struct s and then rename them to camelCase using the serde macro

I modified your code like I would do this, in order to give you an example of how it could be done:

use std::collections::HashMap;

use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize, Debug)]
#[serde(rename_all = "camelCase")]
struct Latest {
    high: Option<u64>,
    high_time: Option<u64>,
    low: Option<u64>,
    low_time: Option<u64>,
}

#[derive(Serialize, Deserialize, Debug)]
struct Data {
    data: HashMap<u64, Latest>,
}

#[cfg(not(target_arch = "wasm32"))]
#[tokio::main]
async fn main() -> Result<(), reqwest::Error> {
    let url = "https://prices.runescape.wiki/api/v1/osrs/latest";
    let res = reqwest::get(url).await?;
    let response = &res.json::<Data>().await?;

    println!("{:#?}", response);

    Ok(())
}