Rust hit an API that returns an array of arrays

Question

I am new to rust and working on a tool which interacts with the Binance API. The API returns a response like so:

{
  "lastUpdateId": 1027024,
  "bids": [
    [
      "4.00000000",     // PRICE
      "431.00000000"    // QTY
    ]
  ],
  "asks": [
    [
      "4.00000200",
      "12.00000000"
    ]
  ]
}

Bids and Asks are an array of arrays. I have to declare the struct for the API response.

I currently have

use reqwest::Error;
use serde::Deserialize;

#[derive(Deserialize, Debug)]
struct Depth {
    lastUpdateId: u32,
    bids: Vec<u64>,
    asks: Vec<u64>,
}

#[tokio::main]
pub async fn order_book() -> Result<(), Error> {
    let request_url = format!("https://api.binance.us/api/v3/depth?symbol=BTCUSD");
    println!("{}", request_url);
    let response = reqwest::get(&request_url).await?;
    println!("Status: {}", response.status());

    let depth: Depth = response.json().await?;
    println!("{:?}", depth);

    Ok(())
}

I believe I am declaring the type for bids and asks incorrectly but I am unable to determine how to declare an array of arrays. I get a response.status of 200, but I am unable to print out the response.json.

Thank You!

Answer 1

Since it returns an array of arrays, you need to nest the types. bids: Vec<Vec<u64>> should work, but since you know each inner array will have two elements, you can make it more efficient with bids: Vec<[u64; 2]> - a dynamically-sized vector of fixed-size arrays, or bids: Vec<(u64, u64)>, a dynamically-sized vector of tuples. You'd also need to update asks similarly.

Your final code could look something like this:

use reqwest::Error;
use serde::Deserialize;

#[derive(Deserialize, Debug)]
struct Depth {
    lastUpdateId: u32,
    bids: Vec<(u64, u64)>,
    asks: Vec<(u64, u64)>,
}

#[tokio::main]
pub async fn order_book() -> Result<(), Error> {
    let request_url = format!("https://api.binance.us/api/v3/depth?symbol=BTCUSD");
    println!("{}", request_url);
    let response = reqwest::get(&request_url).await?;
    println!("Status: {}", response.status());

    let depth: Depth = response.json().await?;
    println!("{:?}", depth);

    Ok(())
}