errors4 solution

exercises/13_error_handling/errors4.rs

@@ -1,16 +1,16 @@
-#[derive(PartialEq, Debug)]
-struct PositiveNonzeroInteger(u64);
-
 #[derive(PartialEq, Debug)]
 enum CreationError {
     Negative,
     Zero,
 }
 
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
 impl PositiveNonzeroInteger {
-    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
+    fn new(value: i64) -> Result<Self, CreationError> {
-        // Hmm... Why is this always returning an Ok value?
+        // TODO: This function shouldn't always return an `Ok`.
-        Ok(PositiveNonzeroInteger(value as u64))
+        Ok(Self(value as u64))
     }
 }
 
@@ -24,11 +24,14 @@ mod tests {
 
     #[test]
     fn test_creation() {
-        assert!(PositiveNonzeroInteger::new(10).is_ok());
         assert_eq!(
-            Err(CreationError::Negative),
+            PositiveNonzeroInteger::new(10),
-            PositiveNonzeroInteger::new(-10)
+            Ok(PositiveNonzeroInteger(10)),
         );
-        assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0));
+        assert_eq!(
+            PositiveNonzeroInteger::new(-10),
+            Err(CreationError::Negative),
+        );
+        assert_eq!(PositiveNonzeroInteger::new(0), Err(CreationError::Zero));
     }
 }

rustlings-macros/info.toml

@@ -683,11 +683,9 @@ name = "errors4"
 dir = "13_error_handling"
 hint = """
 `PositiveNonzeroInteger::new` is always creating a new instance and returning
-an `Ok` result.
+an `Ok` result. But it should be doing some checking, returning an `Err` if
-
+those checks fail, and only returning an `Ok` if those checks determine that
-It should be doing some checking, returning an `Err` result if those checks
+everything is… okay :)"""
-fail, and only returning an `Ok` result if those checks determine that
-everything is... okay :)"""
 
 [[exercises]]
 name = "errors5"

solutions/13_error_handling/errors4.rs

@@ -1 +1,42 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+#[derive(PartialEq, Debug)]
+enum CreationError {
+    Negative,
+    Zero,
+}
+
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
+impl PositiveNonzeroInteger {
+    fn new(value: i64) -> Result<Self, CreationError> {
+        if value == 0 {
+            Err(CreationError::Zero)
+        } else if value < 0 {
+            Err(CreationError::Negative)
+        } else {
+            Ok(Self(value as u64))
+        }
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_creation() {
+        assert_eq!(
+            PositiveNonzeroInteger::new(10),
+            Ok(PositiveNonzeroInteger(10)),
+        );
+        assert_eq!(
+            PositiveNonzeroInteger::new(-10),
+            Err(CreationError::Negative),
+        );
+        assert_eq!(PositiveNonzeroInteger::new(0), Err(CreationError::Zero));
+    }
+}