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Scalable Web Development in Rust

Errors

Learn how to handle errors in Rust.

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Most languages handle errors through exceptions, but Rust does it with a type called Result<T, E>. It’s a data type with two generics: T and E. The T type on the left side is used for the return value, and the E is for the error. We need to return it with the Ok and Error function, respectively.

Rust 1.40.0
// This is an example function that simply takes a parameter as string and return 
// the expected type for "This works" or an error for everything else.
fn this_an_example(some_parameter: &str) -> Result<i32, String> {
    match some_parameter {
        "This works" => Ok(1),
        &_ => Err("An Error".to_string())
    }
}
fn main() {
    println!("Result: {:#?}", this_an_example("This works")); 
    println!("Oh no!: {:#?}", this_an_example("Error")); 
}

If we want to handle the result type, we use pattern matching. If we don’t use ...