diff options
| -rw-r--r-- | exercises/23_conversions/from_into.rs | 62 | ||||
| -rw-r--r-- | rustlings-macros/info.toml | 2 | ||||
| -rw-r--r-- | solutions/23_conversions/from_into.rs | 137 |
3 files changed, 167 insertions, 34 deletions
diff --git a/exercises/23_conversions/from_into.rs b/exercises/23_conversions/from_into.rs index 14a62ba..bc2783a 100644 --- a/exercises/23_conversions/from_into.rs +++ b/exercises/23_conversions/from_into.rs @@ -1,81 +1,79 @@ -// The From trait is used for value-to-value conversions. If From is implemented -// correctly for a type, the Into trait should work conversely. You can read -// more about it at https://doc.rust-lang.org/std/convert/trait.From.html +// The `From` trait is used for value-to-value conversions. If `From` is +// implemented, an implementation of `Into` is automatically provided. +// You can read more about it in the documentation: +// https://doc.rust-lang.org/std/convert/trait.From.html #[derive(Debug)] struct Person { name: String, - age: usize, + age: u8, } -// We implement the Default trait to use it as a fallback -// when the provided string is not convertible into a Person object +// We implement the Default trait to use it as a fallback when the provided +// string is not convertible into a `Person` object. impl Default for Person { - fn default() -> Person { - Person { + fn default() -> Self { + Self { name: String::from("John"), age: 30, } } } -// Your task is to complete this implementation in order for the line `let p1 = -// Person::from("Mark,20")` to compile. Please note that you'll need to parse the -// age component into a `usize` with something like `"4".parse::<usize>()`. The -// outcome of this needs to be handled appropriately. +// TODO: Complete this `From` implementation to be able to parse a `Person` +// out of a string in the form of "Mark,20". +// Note that you'll need to parse the age component into a `u8` with something +// like `"4".parse::<u8>()`. // // Steps: -// 1. If the length of the provided string is 0, then return the default of -// Person. -// 2. Split the given string on the commas present in it. -// 3. Extract the first element from the split operation and use it as the name. -// 4. If the name is empty, then return the default of Person. -// 5. Extract the other element from the split operation and parse it into a -// `usize` as the age. -// If while parsing the age, something goes wrong, then return the default of -// Person. Otherwise, then return an instantiated Person object with the results - +// 1. Split the given string on the commas present in it. +// 2. If the split operation returns less or more than 2 elements, return the +// default of `Person`. +// 3. Use the first element from the split operation as the name. +// 4. If the name is empty, return the default of `Person`. +// 5. Parse the second element from the split operation into a `u8` as the age. +// 6. If parsing the age fails, return the default of `Person`. impl From<&str> for Person { - fn from(s: &str) -> Person {} + fn from(s: &str) -> Self {} } fn main() { - // Use the `from` function + // Use the `from` function. let p1 = Person::from("Mark,20"); - // Since From is implemented for Person, we should be able to use Into + println!("{p1:?}"); + + // Since `From` is implemented for Person, we are able to use `Into`. let p2: Person = "Gerald,70".into(); - println!("{:?}", p1); - println!("{:?}", p2); + println!("{p2:?}"); } #[cfg(test)] mod tests { use super::*; + #[test] fn test_default() { - // Test that the default person is 30 year old John let dp = Person::default(); assert_eq!(dp.name, "John"); assert_eq!(dp.age, 30); } + #[test] fn test_bad_convert() { - // Test that John is returned when bad string is provided let p = Person::from(""); assert_eq!(p.name, "John"); assert_eq!(p.age, 30); } + #[test] fn test_good_convert() { - // Test that "Mark,20" works let p = Person::from("Mark,20"); assert_eq!(p.name, "Mark"); assert_eq!(p.age, 20); } + #[test] fn test_bad_age() { - // Test that "Mark,twenty" will return the default person due to an - // error in parsing age let p = Person::from("Mark,twenty"); assert_eq!(p.name, "John"); assert_eq!(p.age, 30); diff --git a/rustlings-macros/info.toml b/rustlings-macros/info.toml index fce5e5a..b848e0e 100644 --- a/rustlings-macros/info.toml +++ b/rustlings-macros/info.toml @@ -1174,7 +1174,7 @@ Use the `as` operator to cast one of the operands in the last line of the name = "from_into" dir = "23_conversions" hint = """ -Follow the steps provided right before the `From` implementation""" +Follow the steps provided right before the `From` implementation.""" [[exercises]] name = "from_str" diff --git a/solutions/23_conversions/from_into.rs b/solutions/23_conversions/from_into.rs index 4e18198..cec23cb 100644 --- a/solutions/23_conversions/from_into.rs +++ b/solutions/23_conversions/from_into.rs @@ -1 +1,136 @@ -// Solutions will be available before the stable release. Thank you for testing the beta version 🥰 +// The `From` trait is used for value-to-value conversions. If `From` is +// implemented, an implementation of `Into` is automatically provided. +// You can read more about it in the documentation: +// https://doc.rust-lang.org/std/convert/trait.From.html + +#[derive(Debug)] +struct Person { + name: String, + age: u8, +} + +// We implement the Default trait to use it as a fallback when the provided +// string is not convertible into a `Person` object. +impl Default for Person { + fn default() -> Self { + Self { + name: String::from("John"), + age: 30, + } + } +} + +impl From<&str> for Person { + fn from(s: &str) -> Self { + let mut split = s.split(','); + let (Some(name), Some(age), None) = (split.next(), split.next(), split.next()) else { + // ^^^^ there should be no third element + return Self::default(); + }; + + if name.is_empty() { + return Self::default(); + } + + let Ok(age) = age.parse() else { + return Self::default(); + }; + + Self { + name: name.into(), + age, + } + } +} + +fn main() { + // Use the `from` function. + let p1 = Person::from("Mark,20"); + println!("{p1:?}"); + + // Since `From` is implemented for Person, we are able to use `Into`. + let p2: Person = "Gerald,70".into(); + println!("{p2:?}"); +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn test_default() { + let dp = Person::default(); + assert_eq!(dp.name, "John"); + assert_eq!(dp.age, 30); + } + + #[test] + fn test_bad_convert() { + let p = Person::from(""); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_good_convert() { + let p = Person::from("Mark,20"); + assert_eq!(p.name, "Mark"); + assert_eq!(p.age, 20); + } + + #[test] + fn test_bad_age() { + let p = Person::from("Mark,twenty"); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_missing_comma_and_age() { + let p: Person = Person::from("Mark"); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_missing_age() { + let p: Person = Person::from("Mark,"); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_missing_name() { + let p: Person = Person::from(",1"); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_missing_name_and_age() { + let p: Person = Person::from(","); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_missing_name_and_invalid_age() { + let p: Person = Person::from(",one"); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_trailing_comma() { + let p: Person = Person::from("Mike,32,"); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } + + #[test] + fn test_trailing_comma_and_some_string() { + let p: Person = Person::from("Mike,32,dog"); + assert_eq!(p.name, "John"); + assert_eq!(p.age, 30); + } +} |