How to Convert String to Int and int to String in Rust example

How to Convert String to Int and int to String in Rust example

This tutorial covers the following topics:

  • How to parse a string to an integer in Rust?
  • How to convert an integer into a string?
  • How to read input from the console and convert it to an integer?

For example, if the string is 123, It converts to an integer type 123 value.

There are various methods to perform these conversions.

How to Convert a String to an Integer in Rust?

This example demonstrates how to convert a string to an integer using the parse() method. The parse() method returns a Result object. You can use the unwrap method to obtain the integer value.

Here is an example program

fn main() {

    let str = "123";
    let number: u32 = str.parse().unwrap();

    println!("{}", number);
}

Output:

123

In the following example, if the string contains non-numeric characters, the parse() method throws a ParseIntError.

Here’s the program:

fn main() {
    let str = "123abc";
    let number: u32 = str.parse().unwrap();

    println!("{}", number);
}

Running the above program throws a ParseIntError.

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ParseIntError { kind: InvalidDigit }', test.rs:7:35
note: run with the `RUST_BACKTRACE=1` environment variable to display a backtrace

Let’s see a program to read a string from the console and convert it into an integer type in Rust.

  • Print the prompt to the console.
  • Create a mutable string.
  • Read the console input as a string using the read_line() function.
  • Trim the string and call the parse() method, which returns a Result object.
  • Convert the result to type u32.
use std::io;

fn main() {
    println!("Please enter Age?");
    let mut line = String::new();
    io::stdin().read_line(&mut line).expect("Error to read");
    let age: u32 = line.trim().parse().expect("Expect a number");
    println!("{}", age);
}

Please enter Age?
123
123

How to Convert an Integer to a String in Rust?

This example demonstrates how to convert an integer to a string using the to_string() method. The to_string() method returns the string version of the integer.

Here is an example program

fn main() {
    let number: u8 = 11;
    let str: String = number.to_string();
    println!("{}", str);
}

Output:

11

Conclusion

In summary, learn multiple ways to convert strings to and from integer types in Rust with examples.