String to Int in Rust 1.55

In Rust, you can convert a string to an integer by using the parse() method defined on the string slice type &str. This method converts the string slice to the desired integer type using certain rules, and returns a result which can be either Ok(integer) if the conversion is successful or Err if the string slice cannot be parsed.

Here's an example of how to convert a string to an integer in Rust:

let str_num = "123";
let result = str_num.parse::();
match result {
    Ok(num) => println!("The converted integer is {}", num),
    Err(e) => println!("Error: {}", e),
}

In this example, the str_num variable holds the string "123", and we are converting it to a 32-bit integer using the parse() method and the type annotation i32. The result variable holds the result of the conversion, which can either be an Ok variant with the converted integer or an Err variant with an error message.

We then use a match statement to check if the conversion was successful or not. If it was, we print the converted integer. Otherwise, we print the error message.

Another example:

let str_num = "987654321";
let result = str_num.parse::();
if let Ok(num) = result {
    println!("The converted integer is {}", num);
} else {
    println!("Error: {:?}", result.unwrap_err());
}

In this example, we are converting the string "987654321" to a 64-bit unsigned integer using the parse() method and the type annotation u64. Instead of using a match statement, we are using an if let statement to check if the conversion was successful. If it was, we print the converted integer. Otherwise, we print the error message using the unwrap_err() method on the Err variant.