return empty str error.

iriam-profile/src/main.rs

@@ -21,6 +21,7 @@
 //! ```
 //!
 //! For more information, see the documentation of the individual types and methods.
+#![allow(dead_code)]
 use std::fmt::Display;
 
 type S = LiveStreamer;
@@ -172,6 +173,55 @@ impl Builder {
     }
 }
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_builder_with_name() {
+        let streamer = Builder::new().with_name("TestStreamer").build();
+        assert_eq!(streamer.name, Some("TestStreamer".to_string()));
+    }
+
+    #[test]
+    fn test_builder_with_mark() {
+        let streamer = Builder::new().with_mark("TestMark").build();
+        assert_eq!(streamer.mark, Some("TestMark".to_string()));
+    }
+
+    #[test]
+    fn test_builder_with_handle_names() {
+        let handle_names = vec!["@handle1", "@handle2"];
+        let streamer = Builder::new().with_handle_names(handle_names.clone()).build();
+        assert_eq!(streamer.handle_names, Some(handle_names.iter().map(|&s| s.to_string()).collect()));
+    }
+
+    #[test]
+    fn test_builder_full() {
+        let handle_names = vec!["@handle1", "@handle2"];
+        let streamer = Builder::new()
+            .with_name("TestStreamer")
+            .with_mark("TestMark")
+            .with_handle_names(handle_names.clone())
+            .build();
+        assert_eq!(streamer.name, Some("TestStreamer".to_string()));
+        assert_eq!(streamer.mark, Some("TestMark".to_string()));
+        assert_eq!(streamer.handle_names, Some(handle_names.iter().map(|&s| s.to_string()).collect()));
+    }
+
+    #[test]
+    fn test_display() {
+        let handle_names = vec!["@handle1", "@handle2"];
+        let streamer = Builder::new()
+            .with_name("TestStreamer")
+            .with_mark("TestMark")
+            .with_handle_names(handle_names.clone())
+            .build();
+        let display_output = format!("{}", streamer);
+        assert_eq!(display_output, "TestStreamerTestMark\n@handle1, @handle2");
+    }
+}
+
 #[allow(dead_code)]
 fn str_sort() {
     let mut s: Vec<char> =
@@ -292,3 +342,65 @@ fn test_reference_anoymous() {
     println!("{}", container.get_reference());
     println!("{}", container.get_reference_anonymous());
 }
+
+#[derive(Debug)]
+struct A1<'a> {
+    a01: &'a str,
+    a02: i32,
+}
+
+impl<'a> A1<'a> {
+    fn new(a01: &'a str, a02: i32) -> Self {
+        A1 { a01, a02 }
+    }
+
+    fn get_a01(&self) -> &str {
+        self.a01
+    }
+
+    fn set_a01(&mut self, a01: &'a str) {
+        self.a01 = a01;
+    }
+}
+
+#[cfg(test)]
+mod tests_lifetime {
+    use super::*;
+
+    // https://doc.rust-lang.org/book/ch10-03-lifetime-syntax.html
+    //fn return_short_lifetime(v: &[String]) -> &str {
+    //    &v.get(3).unwrap_or_else(|| Box::new(&"".to_string())).as_str()
+    //}
+
+    fn return_short_lifetime_unwrap_or(v: &[String]) -> &str {
+        v.get(3).map(|s| s.as_str()).unwrap_or("")
+    }
+
+    fn return_short_lifetime_return_string(v: &[String]) -> String {
+        v.get(3).map(|s| s.clone()).unwrap_or_else(|| "".to_string())
+    }
+
+    use std::borrow::Cow;
+    fn return_short_lifetime_clone_on_write(v: &[String], index: usize) -> Cow<str> {
+
+        match v.get(index) {
+            Some(s) => Cow::Borrowed(s),
+            None => Cow::Borrowed(""),
+        }
+    }
+
+    #[test]
+    /// Lifetime in deep dive
+    fn test_lifetime_a1() {
+        let v1 = vec!["aaa".to_string(), "bbb".to_string(), "ccc".to_string()];
+        let mut a1 = A1::new(&v1[0], 4);
+        println!("{}", a1.get_a01());
+        assert_eq!(a1.get_a01(), "aaa");
+        a1.set_a01(&v1[1]);
+        assert_eq!(return_short_lifetime_unwrap_or(&v1), "ccc"); // unwrap_or
+        assert_eq!(return_short_lifetime_return_string(&v1), "ccc"); // return String
+        assert_eq!(return_short_lifetime_clone_on_write(&v1, 3), "ccc"); // return Cow<str>
+        let v2 = vec![String::from("aaa"), String::from("bbb"), String::from("ccc")];
+        let _ = return_short_lifetime_clone_on_write(&v2, 3).into_owned();
+    }
+}