Implement 04-enum-formatting

Author: zaaath

Cargo.toml

@@ -25,10 +25,6 @@ path = "src/03-subcommands.rs"
 name = "04-enum-formatting"
 path = "src/04-enum-formatting.rs"
 
-[[bin]]
-name = "05-input-output-files"
-path = "src/05-input-output-files.rs"
-
 [dependencies]
 structopt = { version = "0.3", features = [ "paw" ] }
 paw = "1.0"

src/04-enum-formatting.rs

@@ -1,29 +1,52 @@
 use structopt::StructOpt;
+use std::str::FromStr;
+use std::fmt::{Display, Formatter};
 
 #[derive(Debug, StructOpt)]
 #[structopt(name = "rustcli", about = "Rust CLI examples with StructOpt")]
-enum Opt {
-    #[structopt(about = "Create a new entity")]
-    Create {
-        title: String,
-        text: Option<String>
-    },
-    #[structopt(about = "Edit an existing entity")]
-    Edit {
-        id: i32,
-        title: Option<String>,
-        text: Option<String>
-    },
-    #[structopt(about = "List all entities")]
-    List
+struct Opt {
+    #[structopt(help = "Status of the task (todo, inprogress, blocked, done)")]
+    status: Status
+}
+
+#[derive(Debug)]
+enum Status {
+    ToDo,
+    InProgress,
+    Done,
+    Blocked
+}
+
+impl FromStr for Status {
+    // TODO: understand why I need this line
+    type Err = ParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        // TODO: understand how to convert to lowercase here without String::from later
+        match s {
+            "todo" => Ok(Status::ToDo),
+            "inprogress" => Ok(Status::InProgress),
+            "blocked" => Ok(Status::Blocked),
+            "done" => Ok(Status::Done),
+            // TODO: understand how to simplify this
+            _ => Err(ParseError(String::from("Status must be one of the following: todo, inprogress, blocked, or done.")))
+        }
+    }
+}
+
+// TODO: research ways to reuse well-known errors
+#[derive(Debug)]
+struct ParseError(String);
+// TODO: understand the difference between std::error::Error and std::fmt::Error
+impl std::error::Error for ParseError { }
+impl Display for ParseError {
+    // TODO: understand why lifetime specifier is required here
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> {
+        write!(f, "{}", self.0)
+    }
 }
 
 fn main() {
     let opt = Opt::from_args();
     println!("opt = {:?}", opt);
-    match opt {
-        Opt::Create { title, text } => println!("Processing Opt::Create with title = {}, text = {:?}", title, text),
-        Opt::Edit { .. } => println!("Processing Opt::Edit with {:?}", opt),
-        Opt::List => println!("Processing Opt::List"),
-    }
 }