Chaining Results with the ? Operator

Snippet

Chaining Results with the ? Operator

The ? operator is a powerful error propagation tool that unwraps Ok values or returns Err values early from functions. It's especially useful when chaining multiple operations that might fail, eliminating verbose match statements and if let chains.

snippet.rs
rust
use std::num::ParseIntError;
 
fn parse_and_add(a: &str, b: &str) -> Result<i32, ParseIntError> {
    let a: i32 = a.parse()?;
    let b: i32 = b.parse()?;
    Ok(a + b)
}
 
fn main() {
    let result = parse_and_add("42", "18");
    println!("{:?}", result);
}

Breakdown

use std::num::ParseIntError;

Imports the ParseIntError type for explicit error handling

fn parse_and_add(a: &str, b: &str) -> Result<i32, ParseIntError>

Function signature declares the error type explicitly

let a: i32 = a.parse()?;

? unwraps the Ok value or returns Err immediately

let b: i32 = b.parse()?;

Second parse can also fail, ? handles it the same way

Ok(a + b)

Returns the sum wrapped in Ok on success

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Chaining Results with the ? Operator

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