rustlings/exercises/conversions/from_str.rs

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// 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;
#[derive(Debug)]
struct Person {
name: String,
age: usize,
}
// 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
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// 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> {
}
}
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());
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}
#[test]
fn invalid_age() {
assert!("John,twenty".parse::<Person>().is_err());
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}
#[test]
fn missing_comma_and_age() {
assert!("John".parse::<Person>().is_err());
}
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#[test]
fn missing_name() {
assert!(",1".parse::<Person>().is_err());
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}
#[test]
fn missing_name_and_age() {
assert!(",".parse::<Person>().is_err());
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}
#[test]
fn missing_name_and_invalid_age() {
assert!(",one".parse::<Person>().is_err());
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}
#[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());
}
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}