User input and string to integer conversion?

help
1

Hello there!
I am here to ask about, how to get user input and convert it to an integer by using parse and trim functions?

2

The simple way if you don't case about error handling is

let user_input: &str;
let user_input = user_input.parse::<i32>().expect("Invalid input");

if you want to supply a default on invalid input

let user_input: &str;
let default_value: i32;
let user_input = user_input.parse::<i32>().unwrap_or(default_value);

Once you start to care about error handling

let user_input: &str;
let user_input = if let Ok(user_input) = user_input.parse::<i32>() {
    user_input
} else {
    // error handling
};

You can use any of the integer types instead of i32 in the examples above

2 Likes
3

To get user input, see the std::io module. A simple example looks like:

use std::{io::stdin, error::Error};

fn main() -> Result<(), Box<dyn Error>> {
    let mut input = String::new();
    stdin().read_line(&mut input)?;
    
    let num: i32 = input.trim().parse()?;
    
    println!("{} squared is {}", num, num * num);
    
    Ok(())
}

Playground

2 Likes
4

Also work through the guessing game example here. It covers basic string parsing into numbers and concepts related to it on a very basic level.

5

Thank you so much @L0uisc.

6

Thank you very much @mbrubeck.

7

Thank you very much @RustyYato.

8

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