Started Rust in Action MEAP.

1 files changed, 49 insertions, 0 deletions

diff --git a/meap/meap-code/ch3/ch3-implementing-display.rs b/meap/meap-code/ch3/ch3-implementing-display.rs
new file mode 100644
index 0000000..8537bd9
--- /dev/null
+++ b/meap/meap-code/ch3/ch3-implementing-display.rs
@@ -0,0 +1,49 @@
+#![allow(dead_code)] // <1> Silence warnings related to FileState::Open not being used

+

+use std::fmt;  // <2> Bring the `std::fmt` crate into local scope, allowing us to make use of `fmt::Result`

+use std::fmt::{Display};  // <3> Bring `Display` into local scope, avoiding the need for us to prefix it as `fmt::Display` in our code

+

+#[derive(Debug,PartialEq)]

+enum FileState {

+  Open,

+  Closed,

+}

+

+#[derive(Debug)]

+struct File {

+  name: String,

+  data: Vec<u8>,

+  state: FileState,

+}

+

+impl Display for FileState {

+   fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

+     match *self {

+         FileState::Open => write!(f, "OPEN"),     // <4> Sneakily, we can make use of `write!` to do the grunt work for us. Strings already implement `Display` themselves, so there's very little left for us to do.

+         FileState::Closed => write!(f, "CLOSED"), // <4>

+     }

+   }

+}

+

+impl Display for File {

+   fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

+      write!(f, "<{} ({})>", self.name, self.state)  // <5> We can rely on the FileState Display implementation in our own code 

+   }

+}

+

+impl File {

+  fn new(name: &str) -> File {

+    File {

+        name: String::from(name), 

+        data: Vec::new(), 

+        state: FileState::Closed

+    }

+  }

+}

+

+fn main() {

+  let f5 = File::new("f5.txt");

+  //...

+  println!("{:?}", f5); // <1>

+  println!("{}", f5); // <1>

+}
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