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f7b50183f4
- Replace From<&str> trait with TryFrom<&str> for proper error handling - Add ParsePersonError enum with BadLen, NoName, and ParseInt variants - Update all tests to expect appropriate errors instead of default Person values - Maintain same error handling pattern as from_str exercise - Add required imports for TryFrom and TryInto traits
117 lines
3.1 KiB
Rust
117 lines
3.1 KiB
Rust
// The `From` trait is used for value-to-value conversions. If `From` is
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// implemented, an implementation of `Into` is automatically provided.
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// You can read more about it in the documentation:
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// https://doc.rust-lang.org/std/convert/trait.From.html
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use std::convert::{TryFrom, TryInto};
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use std::num::ParseIntError;
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#[derive(Debug, PartialEq)]
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struct Person {
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name: String,
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age: u8,
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}
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// We will use this error type for the `TryFrom` implementation.
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#[derive(Debug, PartialEq)]
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enum ParsePersonError {
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// Incorrect number of fields
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BadLen,
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// Empty name field
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NoName,
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// Wrapped error from parse::<u8>()
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ParseInt(ParseIntError),
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}
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// TODO: Complete this `TryFrom` implementation to be able to parse a `Person`
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// out of a string in the form of "Mark,20".
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// Note that you'll need to parse the age component into a `u8` with something
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// like `"4".parse::<u8>()`.
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//
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// Steps:
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// 1. Split the given string on the commas present in it.
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// 2. If the split operation returns less or more than 2 elements, return the
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// error `ParsePersonError::BadLen`.
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// 3. Use the first element from the split operation as the name.
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// 4. If the name is empty, return the error `ParsePersonError::NoName`.
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// 5. Parse the second element from the split operation into a `u8` as the age.
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// 6. If parsing the age fails, return the error `ParsePersonError::ParseInt`.
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impl TryFrom<&str> for Person {
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type Error = ParsePersonError;
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fn try_from(s: &str) -> Result<Self, Self::Error> {}
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}
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fn main() {
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// Use the `try_from` function.
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let p1 = Person::try_from("Mark,20");
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println!("{p1:?}");
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// Since `TryFrom` is implemented for Person, we are able to use `try_into`.
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let p2: Result<Person, ParsePersonError> = "Gerald,70".try_into();
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println!("{p2:?}");
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use ParsePersonError::*;
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#[test]
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fn empty_input() {
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assert_eq!(Person::try_from(""), Err(BadLen));
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}
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#[test]
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fn good_input() {
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let p = Person::try_from("John,32");
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assert!(p.is_ok());
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let p = p.unwrap();
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 32);
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}
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#[test]
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fn missing_age() {
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assert!(matches!(Person::try_from("John,"), Err(ParseInt(_))));
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}
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#[test]
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fn invalid_age() {
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assert!(matches!(Person::try_from("John,twenty"), Err(ParseInt(_))));
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}
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#[test]
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fn missing_comma_and_age() {
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assert_eq!(Person::try_from("John"), Err(BadLen));
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}
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#[test]
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fn missing_name() {
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assert_eq!(Person::try_from(",1"), Err(NoName));
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}
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#[test]
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fn missing_name_and_age() {
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assert!(matches!(Person::try_from(","), Err(NoName | ParseInt(_))));
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}
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#[test]
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fn missing_name_and_invalid_age() {
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assert!(matches!(
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Person::try_from(",one"),
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Err(NoName | ParseInt(_)),
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));
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}
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#[test]
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fn trailing_comma() {
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assert_eq!(Person::try_from("John,32,"), Err(BadLen));
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}
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#[test]
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fn trailing_comma_and_some_string() {
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assert_eq!(Person::try_from("John,32,man"), Err(BadLen));
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}
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}
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