rustlings/error_handling/errors1.rs

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2018-02-22 09:09:53 +03:00
// errors1.rs
// This function refuses to generate text to be printed on a nametag if
// you pass it an empty string. It'd be nicer if it explained what the problem
// was, instead of just sometimes returning `None`. The 2nd test currently
// does not compile or pass, but it illustrates the behavior we would like
// this function to have.
// Scroll down for hints!!!
pub fn generate_nametag_text(name: String) -> Option<String> {
if name.len() > 0 {
Some(format!("Hi! My name is {}", name))
} else {
// Empty names aren't allowed.
None
}
}
#[cfg(test)]
mod tests {
use super::*;
// This test passes initially if you comment out the 2nd test.
// You'll need to update what this test expects when you change
// the function under test!
#[test]
fn generates_nametag_text_for_a_nonempty_name() {
assert_eq!(
generate_nametag_text("Beyoncé".into()),
Some("Hi! My name is Beyoncé".into())
);
}
#[test]
fn explains_why_generating_nametag_text_fails() {
assert_eq!(
generate_nametag_text("".into()),
Err("`name` was empty; it must be nonempty.".into())
);
}
}
// `Err` is one of the variants of `Result`, so what the 2nd test is saying
// is that `generate_nametag_text` should return a `Result` instead of an
// `Option`.
// To make this change, you'll need to:
// - update the return type in the function signature to be a Result that
// could be the variants `Ok(String)` and `Err(String)`
// - change the body of the function to return `Ok(stuff)` where it currently
// returns `Some(stuff)`
// - change the body of the function to return `Err(error message)` where it
// currently returns `None`
// - change the first test to expect `Ok(stuff)` where it currently expects
// `Some(stuff)`.