100 exercises to learn Rust

helpers/ticket_fields/src/title.rs

@@ -0,0 +1,75 @@
+use std::convert::TryFrom;
+
+#[derive(Debug, PartialEq, Clone, Eq)]
+pub struct TicketTitle(String);
+
+#[derive(Debug, thiserror::Error)]
+pub enum TicketTitleError {
+    #[error("The title cannot be empty")]
+    Empty,
+    #[error("The title cannot be longer than 50 characters")]
+    TooLong,
+}
+
+impl TryFrom<String> for TicketTitle {
+    type Error = TicketTitleError;
+
+    fn try_from(value: String) -> Result<Self, Self::Error> {
+        validate(&value)?;
+        Ok(Self(value))
+    }
+}
+
+impl TryFrom<&str> for TicketTitle {
+    type Error = TicketTitleError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        validate(value)?;
+        Ok(Self(value.to_string()))
+    }
+}
+
+fn validate(title: &str) -> Result<(), TicketTitleError> {
+    if title.is_empty() {
+        Err(TicketTitleError::Empty)
+    } else if title.len() > 50 {
+        Err(TicketTitleError::TooLong)
+    } else {
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use common::{overly_long_title, valid_title};
+    use std::convert::TryFrom;
+
+    #[test]
+    fn test_try_from_string() {
+        let input = valid_title();
+        let title = TicketTitle::try_from(input.clone()).unwrap();
+        assert_eq!(title.0, input);
+    }
+
+    #[test]
+    fn test_try_from_empty_string() {
+        let err = TicketTitle::try_from("".to_string()).unwrap_err();
+        assert_eq!(err.to_string(), "The title cannot be empty");
+    }
+
+    #[test]
+    fn test_try_from_long_string() {
+        let err = TicketTitle::try_from(overly_long_title()).unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "The title cannot be longer than 50 characters"
+        );
+    }
+
+    #[test]
+    fn test_try_from_str() {
+        let title = TicketTitle::try_from("A title").unwrap();
+        assert_eq!(title.0, "A title");
+    }
+}