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137 lines
3.2 KiB
Rust
137 lines
3.2 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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#[derive(Debug)]
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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 implement the Default trait to use it as a fallback when the provided
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// string is not convertible into a `Person` object.
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impl Default for Person {
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fn default() -> Self {
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Self {
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name: String::from("John"),
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age: 30,
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}
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}
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}
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impl From<&str> for Person {
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fn from(s: &str) -> Self {
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let mut split = s.split(',');
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let (Some(name), Some(age), None) = (split.next(), split.next(), split.next()) else {
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// ^^^^ there should be no third element
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return Self::default();
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};
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if name.is_empty() {
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return Self::default();
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}
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let Ok(age) = age.parse() else {
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return Self::default();
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};
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Self {
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name: name.into(),
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age,
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}
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}
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}
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fn main() {
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// Use the `from` function.
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let p1 = Person::from("Mark,20");
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println!("{p1:?}");
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// Since `From` is implemented for Person, we are able to use `Into`.
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let p2: Person = "Gerald,70".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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#[test]
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fn test_default() {
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let dp = Person::default();
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assert_eq!(dp.name, "John");
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assert_eq!(dp.age, 30);
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}
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#[test]
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fn test_bad_convert() {
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let p = Person::from("");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_good_convert() {
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let p = Person::from("Mark,20");
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assert_eq!(p.name, "Mark");
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assert_eq!(p.age, 20);
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}
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#[test]
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fn test_bad_age() {
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let p = Person::from("Mark,twenty");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_missing_comma_and_age() {
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let p: Person = Person::from("Mark");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_missing_age() {
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let p: Person = Person::from("Mark,");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_missing_name() {
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let p: Person = Person::from(",1");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_missing_name_and_age() {
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let p: Person = Person::from(",");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_missing_name_and_invalid_age() {
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let p: Person = Person::from(",one");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_trailing_comma() {
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let p: Person = Person::from("Mike,32,");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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#[test]
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fn test_trailing_comma_and_some_string() {
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let p: Person = Person::from("Mike,32,dog");
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assert_eq!(p.name, "John");
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assert_eq!(p.age, 30);
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}
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}
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