Multidimensional array into multidimensional HashMap in Rust

October 28, 2022

use std::collections::HashMap;

fn main() {
    let tuples = [("outer1", [("inner1", 1), ("inner2", 2), ("inner3", 3)])];
    let m: HashMap<_, _> = tuples.into_iter().collect();
    println!("{:?}", m);
}

This code prints the following: {"outer1": [("inner1", 1), ("inner2", 2), ("inner3", 3)]}

That is a HashMap of strings to an array of tuples. Instead, I want to create a HashMap of the inner layer as well, i.e.: {"outer1": {"inner1": 1, "inner2": 2, "inner3": 3}}

Playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=9ef9dd56592ac820a86d529dba085129

Is there a clean, idiomatic way to accomplish this?

>Solution :

Map over the entries and turn those into a hashmap as well:

let m: HashMap<_, HashMap<_, _>> =
    tuples
        .into_iter()
        .map(|(key, entries)| (key, entries.into_iter().collect()))
        .collect();

Playground