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108 lines
2.8 KiB
Rust
108 lines
2.8 KiB
Rust
// This does practically the same thing that TryFrom<&str> does.
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// Additionally, upon implementing FromStr, you can use the `parse` method
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// on strings to generate an object of the implementor type.
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// You can read more about it at https://doc.rust-lang.org/std/str/trait.FromStr.html
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use std::str::FromStr;
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#[derive(Debug)]
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struct Person {
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name: String,
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age: usize,
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}
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// Steps:
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// 1. If the length of the provided string is 0, then return an error
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// 2. Split the given string on the commas present in it
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// 3. Extract the first element from the split operation and use it as the name
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// 4. If the name is empty, then return an error
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// 5. Extract the other element from the split operation and parse it into a `usize` as the age
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// with something like `"4".parse::<usize>()`.
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// If while parsing the age, something goes wrong, then return an error
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// Otherwise, then return a Result of a Person object
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impl FromStr for Person {
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type Err = String;
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fn from_str(s: &str) -> Result<Person, Self::Err> {
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if s.len() == 0 {
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return Err("Please provide non empty string".to_string());
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}
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let person_vec: Vec<&str> = s.split(",").collect();
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if (person_vec[0].len() == 0) | (person_vec[1].len() == 0) {
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return Err(format!(
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"Missing name or age in the string: {:?}",
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person_vec
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));
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}
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let name: &str = person_vec[0];
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let age = match person_vec[1].parse::<usize>() {
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Ok(age) => age,
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Err(_) => return Err(format!("Cannot parse {:?} to usize", person_vec[1])),
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};
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Ok(Person {
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name: name.to_string(),
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age: age,
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})
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}
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}
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fn main() {
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let p = "Mark,20".parse::<Person>().unwrap();
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println!("{:?}", p);
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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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#[test]
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fn empty_input() {
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assert!("".parse::<Person>().is_err());
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}
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#[test]
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fn good_input() {
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let p = "John,32".parse::<Person>();
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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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#[should_panic]
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fn missing_age() {
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"John,".parse::<Person>().unwrap();
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}
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#[test]
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#[should_panic]
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fn invalid_age() {
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"John,twenty".parse::<Person>().unwrap();
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}
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#[test]
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#[should_panic]
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fn missing_comma_and_age() {
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"John".parse::<Person>().unwrap();
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}
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#[test]
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#[should_panic]
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fn missing_name() {
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",1".parse::<Person>().unwrap();
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}
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#[test]
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#[should_panic]
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fn missing_name_and_age() {
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",".parse::<Person>().unwrap();
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}
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#[test]
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#[should_panic]
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fn missing_name_and_invalid_age() {
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",one".parse::<Person>().unwrap();
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}
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}
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