1 files changed, 72 insertions, 0 deletions
diff --git a/error_handling/errors1.rs b/error_handling/errors1.rs
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+++ b/error_handling/errors1.rs
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+// This function refuses to generate text to be printed on a nametag if
+// you pass it an empty string. It'd be nicer if it explained what the problem
+// was, instead of just sometimes returning `None`. The 2nd test currently
+// does not compile or pass, but it illustrates the behavior we would like
+// this function to have.
+// Scroll down for hints!!!
+
+pub fn generate_nametag_text(name: String) -> Option<String> {
+    if name.len() > 0 {
+        Some(format!("Hi! My name is {}", name))
+    } else {
+        // Empty names aren't allowed.
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // This test passes initially if you comment out the 2nd test.
+    // You'll need to update what this test expects when you change
+    // the function under test!
+    #[test]
+    fn generates_nametag_text_for_a_nonempty_name() {
+        assert_eq!(
+            generate_nametag_text("Beyoncé".into()),
+            Some("Hi! My name is Beyoncé".into())
+        );
+    }
+
+    #[test]
+    fn explains_why_generating_nametag_text_fails() {
+        assert_eq!(
+            generate_nametag_text("".into()),
+            Err("`name` was empty; it must be nonempty.".into())
+        );
+    }
+}
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+// `Err` is one of the variants of `Result`, so what the 2nd test is saying
+// is that `generate_nametag_text` should return a `Result` instead of an
+// `Option`.
+
+// To make this change, you'll need to:
+// - update the return type in the function signature to be a Result that
+//   could be the variants `Ok(String)` and `Err(String)`
+// - change the body of the function to return `Ok(stuff)` where it currently
+//   returns `Some(stuff)`
+// - change the body of the function to return `Err(error message)` where it
+//   currently returns `None`
+// - change the first test to expect `Ok(stuff)` where it currently expects
+//   `Some(stuff)`.