114 lines
3.0 KiB
Rust
114 lines
3.0 KiB
Rust
// This is similar to the previous `from_into` exercise. But this time, we'll
|
|
// implement `FromStr` and return errors instead of falling back to a default
|
|
// value. Additionally, upon implementing `FromStr`, you can use the `parse`
|
|
// method on strings to generate an object of the implementor type. You can read
|
|
// more about it in the documentation:
|
|
// https://doc.rust-lang.org/std/str/trait.FromStr.html
|
|
|
|
use std::num::ParseIntError;
|
|
use std::str::FromStr;
|
|
|
|
#[derive(Debug, PartialEq)]
|
|
struct Person {
|
|
name: String,
|
|
age: u8,
|
|
}
|
|
|
|
// We will use this error type for the `FromStr` implementation.
|
|
#[derive(Debug, PartialEq)]
|
|
enum ParsePersonError {
|
|
// Incorrect number of fields
|
|
BadLen,
|
|
// Empty name field
|
|
NoName,
|
|
// Wrapped error from parse::<u8>()
|
|
ParseInt(ParseIntError),
|
|
}
|
|
|
|
// TODO: Complete this `From` implementation to be able to parse a `Person`
|
|
// out of a string in the form of "Mark,20".
|
|
// Note that you'll need to parse the age component into a `u8` with something
|
|
// like `"4".parse::<u8>()`.
|
|
//
|
|
// Steps:
|
|
// 1. Split the given string on the commas present in it.
|
|
// 2. If the split operation returns less or more than 2 elements, return the
|
|
// error `ParsePersonError::BadLen`.
|
|
// 3. Use the first element from the split operation as the name.
|
|
// 4. If the name is empty, return the error `ParsePersonError::NoName`.
|
|
// 5. Parse the second element from the split operation into a `u8` as the age.
|
|
// 6. If parsing the age fails, return the error `ParsePersonError::ParseInt`.
|
|
impl FromStr for Person {
|
|
type Err = ParsePersonError;
|
|
|
|
fn from_str(s: &str) -> Result<Self, Self::Err> {}
|
|
}
|
|
|
|
fn main() {
|
|
let p = "Mark,20".parse::<Person>();
|
|
println!("{p:?}");
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
use ParsePersonError::*;
|
|
|
|
#[test]
|
|
fn empty_input() {
|
|
assert_eq!("".parse::<Person>(), Err(BadLen));
|
|
}
|
|
|
|
#[test]
|
|
fn good_input() {
|
|
let p = "John,32".parse::<Person>();
|
|
assert!(p.is_ok());
|
|
let p = p.unwrap();
|
|
assert_eq!(p.name, "John");
|
|
assert_eq!(p.age, 32);
|
|
}
|
|
|
|
#[test]
|
|
fn missing_age() {
|
|
assert!(matches!("John,".parse::<Person>(), Err(ParseInt(_))));
|
|
}
|
|
|
|
#[test]
|
|
fn invalid_age() {
|
|
assert!(matches!("John,twenty".parse::<Person>(), Err(ParseInt(_))));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_comma_and_age() {
|
|
assert_eq!("John".parse::<Person>(), Err(BadLen));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name() {
|
|
assert_eq!(",1".parse::<Person>(), Err(NoName));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name_and_age() {
|
|
assert!(matches!(",".parse::<Person>(), Err(NoName | ParseInt(_))));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name_and_invalid_age() {
|
|
assert!(matches!(
|
|
",one".parse::<Person>(),
|
|
Err(NoName | ParseInt(_)),
|
|
));
|
|
}
|
|
|
|
#[test]
|
|
fn trailing_comma() {
|
|
assert_eq!("John,32,".parse::<Person>(), Err(BadLen));
|
|
}
|
|
|
|
#[test]
|
|
fn trailing_comma_and_some_string() {
|
|
assert_eq!("John,32,man".parse::<Person>(), Err(BadLen));
|
|
}
|
|
}
|