123 lines
3.3 KiB
Rust
123 lines
3.3 KiB
Rust
// from_str.rs
|
|
// This is similar to from_into.rs, 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 at 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: usize,
|
|
}
|
|
|
|
// We will use this error type for the `FromStr` implementation.
|
|
#[derive(Debug, PartialEq)]
|
|
enum ParsePersonError {
|
|
// Empty input string
|
|
Empty,
|
|
// Incorrect number of fields
|
|
BadLen,
|
|
// Empty name field
|
|
NoName,
|
|
// Wrapped error from parse::<usize>()
|
|
ParseInt(ParseIntError),
|
|
}
|
|
|
|
// I AM NOT DONE
|
|
|
|
// Steps:
|
|
// 1. If the length of the provided string is 0, an error should be returned
|
|
// 2. Split the given string on the commas present in it
|
|
// 3. Only 2 elements should be returned from the split, otherwise return an error
|
|
// 4. Extract the first element from the split operation and use it as the name
|
|
// 5. Extract the other element from the split operation and parse it into a `usize` as the age
|
|
// with something like `"4".parse::<usize>()`
|
|
// 6. If while extracting the name and the age something goes wrong, an error should be returned
|
|
// If everything goes well, then return a Result of a Person object
|
|
|
|
impl FromStr for Person {
|
|
type Err = ParsePersonError;
|
|
fn from_str(s: &str) -> Result<Person, Self::Err> {
|
|
}
|
|
}
|
|
|
|
fn main() {
|
|
let p = "Mark,20".parse::<Person>().unwrap();
|
|
println!("{:?}", p);
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn empty_input() {
|
|
assert_eq!("".parse::<Person>(), Err(ParsePersonError::Empty));
|
|
}
|
|
#[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(ParsePersonError::ParseInt(_))
|
|
));
|
|
}
|
|
|
|
#[test]
|
|
fn invalid_age() {
|
|
assert!(matches!(
|
|
"John,twenty".parse::<Person>(),
|
|
Err(ParsePersonError::ParseInt(_))
|
|
));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_comma_and_age() {
|
|
assert_eq!("John".parse::<Person>(), Err(ParsePersonError::BadLen));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name() {
|
|
assert_eq!(",1".parse::<Person>(), Err(ParsePersonError::NoName));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name_and_age() {
|
|
assert!(matches!(
|
|
",".parse::<Person>(),
|
|
Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
|
|
));
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name_and_invalid_age() {
|
|
assert!(matches!(
|
|
",one".parse::<Person>(),
|
|
Err(ParsePersonError::NoName | ParsePersonError::ParseInt(_))
|
|
));
|
|
}
|
|
|
|
#[test]
|
|
fn trailing_comma() {
|
|
assert_eq!("John,32,".parse::<Person>(), Err(ParsePersonError::BadLen));
|
|
}
|
|
|
|
#[test]
|
|
fn trailing_comma_and_some_string() {
|
|
assert_eq!(
|
|
"John,32,man".parse::<Person>(),
|
|
Err(ParsePersonError::BadLen)
|
|
);
|
|
}
|
|
}
|