map Get value in Rust 1.55

To get the value of a key in a hash in Rust 1.55, you can use the get method of the HashMap struct.

Here's an example code snippet to demonstrate how to use get method:

use std::collections::HashMap;
fn main() {

    let mut fruit_counts = HashMap::new();

    fruit_counts.insert("apple", 3);

    fruit_counts.insert("banana", 2);

    fruit_counts.insert("orange", 1);
let count_of_apples = fruit_counts.get("apple");
match count_of_apples {

        Some(count) => println!("Number of apples: {}", count),

        None => println!("There are no apples.")

    }

}

In the example above, we create a new HashMap called fruit_counts and insert some key-value pairs into it using the insert method. We then retrieve the value associated with the key "apple" using the get method and store it in the variable count_of_apples.

Since the get method returns an Option<&V> type, we use a match statement to handle both cases where the key is found and where it is not found. If the key is found, we print the value associated with it, otherwise, we print a message indicating that the key was not found.

Note that the get method returns a reference to the value associated with the key, so if you want to modify the value, you will need to use an appropriate reference. For example:

if let Some(count) = fruit_counts.get_mut("apple") {
    *count += 1;
}

In the code above, we use the get_mut method to get a mutable reference to the value associated with the key "apple", and we then increment the value by one using the * operator to dereference the mutable reference.