ex(14): generics

.rustlings-state.txt

···
 DON'T EDIT THIS FILE!
 
-generics1
+traits1
 
 intro1
 intro2
···
 errors3
 errors4
 errors5
-errors6
+errors6
+generics1
+generics2

exercises/14_generics/generics1.rs

···
     // TODO: Fix the compiler error by annotating the type of the vector
     // `Vec<T>`. Choose `T` as some integer type that can be created from
     // `u8` and `i8`.
-    let mut numbers = Vec::new();
+    let mut numbers: Vec<i16> = Vec::new();
 
     // Don't change the lines below.
     let n1: u8 = 42;

exercises/14_generics/generics2.rs

···
 // This powerful wrapper provides the ability to store a positive integer value.
 // TODO: Rewrite it using a generic so that it supports wrapping ANY type.
-struct Wrapper {
-    value: u32,
+struct Wrapper<T> {
+    value: T,
 }
 
 // TODO: Adapt the struct's implementation to be generic over the wrapped value.
-impl Wrapper {
-    fn new(value: u32) -> Self {
+impl<T> Wrapper<T> {
+    fn new(value: T) -> Self {
         Wrapper { value }
     }
 }

solutions/14_generics/generics1.rs

···
+// `Vec<T>` is generic over the type `T`. In most cases, the compiler is able to
+// infer `T`, for example after pushing a value with a concrete type to the vector.
+// But in this exercise, the compiler needs some help through a type annotation.
+
 fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+    // `u8` and `i8` can both be converted to `i16`.
+    let mut numbers: Vec<i16> = Vec::new();
+    //             ^^^^^^^^^^ added
+
+    // Don't change the lines below.
+    let n1: u8 = 42;
+    numbers.push(n1.into());
+    let n2: i8 = -1;
+    numbers.push(n2.into());
+
+    println!("{numbers:?}");
 }

solutions/14_generics/generics2.rs

···
+struct Wrapper<T> {
+    value: T,
+}
+
+impl<T> Wrapper<T> {
+    fn new(value: T) -> Self {
+        Wrapper { value }
+    }
+}
+
 fn main() {
-    // DON'T EDIT THIS SOLUTION FILE!
-    // It will be automatically filled after you finish the exercise.
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn store_u32_in_wrapper() {
+        assert_eq!(Wrapper::new(42).value, 42);
+    }
+
+    #[test]
+    fn store_str_in_wrapper() {
+        assert_eq!(Wrapper::new("Foo").value, "Foo");
+    }
 }