from_into solution

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);

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"

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);
+    }
+}