rustHow to access a mutable index in a Rust HashMap?

Accessing a mutable index in a Rust HashMap can be done using the entry method. This method returns a mutable reference to the corresponding value in the HashMap.

Example code

use std::collections::HashMap;

let mut map = HashMap::new();
map.insert("key", "value");

let entry = map.entry("key").or_insert("new value");
*entry = "updated value";

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

Output example

{"key": "updated value"}

Code explanation

1. let mut map = HashMap::new(); - creates a new empty HashMap.
2. map.insert("key", "value"); - inserts a key-value pair into the HashMap.
3. let entry = map.entry("key").or_insert("new value"); - returns a mutable reference to the corresponding value in the HashMap. If the key does not exist, a new key-value pair is inserted with the given value.
4. *entry = "updated value"; - updates the value of the key-value pair.
5. println!("{:?}", map); - prints the HashMap.

Helpful links

• Rust HashMap documentation

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