Convert a String to int in Rust?

rust
mtahmed picture mtahmed · Nov 20, 2014 · Viewed 145.8k times · Source

Note: this question contains deprecated pre-1.0 code! The answer is correct, though.

To convert a str to an int in Rust, I can do this:

let my_int = from_str::<int>(my_str);

The only way I know how to convert a String to an int is to get a slice of it and then use from_str on it like so:

let my_int = from_str::<int>(my_string.as_slice());

Is there a way to directly convert a String to an int?

Answer

John Vrbanac picture John Vrbanac · Dec 29, 2014

You can directly convert to an int using the str::parse::<T>() method.

let my_string = "27".to_string();  // `parse()` works with `&str` and `String`!
let my_int = my_string.parse::<i32>().unwrap();

You can either specify the type to parse to with the turbofish operator (::<>) as shown above or via explicit type annotation:

let my_int: i32 = my_string.parse().unwrap();

As mentioned in the comments, parse() returns a Result. This result will be an Err if the string couldn't be parsed as the type specified (for example, the string "peter" can't be parsed as i32).

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