mirror of
https://github.com/rust-lang/rustlings.git
synced 2026-01-11 13:19:18 +00:00
127 lines
3.3 KiB
Rust
127 lines
3.3 KiB
Rust
// This does practically the same thing that TryFrom<&str> does.
|
|
// 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::error;
|
|
use std::str::FromStr;
|
|
use std::fmt::Display;
|
|
use std::fmt::Formatter;
|
|
|
|
#[derive(Debug)]
|
|
struct Person {
|
|
name: String,
|
|
age: usize,
|
|
}
|
|
|
|
#[derive(Debug)]
|
|
struct ParseError {
|
|
reason: String
|
|
}
|
|
|
|
impl Display for ParseError {
|
|
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error>
|
|
{
|
|
f.write_str("fucked up");
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
impl error::Error for ParseError {
|
|
|
|
}
|
|
// 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>()`
|
|
// 5. 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 = Box<dyn error::Error>;
|
|
fn from_str(s: &str) -> Result<Person, Self::Err> {
|
|
let mut idx = -1;
|
|
for (i, &b) in s.as_bytes().iter().enumerate() {
|
|
if b',' == b {
|
|
idx = i as i32;
|
|
}
|
|
}
|
|
if idx <= 0 || idx as usize == (s.len() - 1) {
|
|
Err(Box::new(ParseError{reason:String::from("Not divided into two")}))
|
|
}else {
|
|
let idx = idx as usize;
|
|
match s[(idx +1)..].parse::<usize>() {
|
|
Ok(age) => Ok(Person{
|
|
name: s[..idx ].into(),
|
|
age: age
|
|
}),
|
|
Err(error) => Err(Box::new(ParseError{reason:String::from("invalid age string")}))
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn main() {
|
|
let p = "Mark,20".parse::<Person>().unwrap();
|
|
println!("{:?}", p);
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn empty_input() {
|
|
assert!("".parse::<Person>().is_err());
|
|
}
|
|
#[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!("John,".parse::<Person>().is_err());
|
|
}
|
|
|
|
#[test]
|
|
fn invalid_age() {
|
|
assert!("John,twenty".parse::<Person>().is_err());
|
|
}
|
|
|
|
#[test]
|
|
fn missing_comma_and_age() {
|
|
assert!("John".parse::<Person>().is_err());
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name() {
|
|
assert!(",1".parse::<Person>().is_err());
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name_and_age() {
|
|
assert!(",".parse::<Person>().is_err());
|
|
}
|
|
|
|
#[test]
|
|
fn missing_name_and_invalid_age() {
|
|
assert!(",one".parse::<Person>().is_err());
|
|
}
|
|
|
|
#[test]
|
|
fn trailing_comma() {
|
|
assert!("John,32,".parse::<Person>().is_err());
|
|
}
|
|
|
|
#[test]
|
|
fn trailing_comma_and_some_string() {
|
|
assert!("John,32,man".parse::<Person>().is_err());
|
|
}
|
|
}
|