File reading and error handling using ?

[learn-rust.git] / src / main.rs

diff --git a/src/main.rs b/src/main.rs
index 973bb2e6c8a3ff790ed25a03f690ea48c6a29084..441cc79a44db49e65227afdacfa575de42e96fb9 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -69,6 +69,13 @@ fn test_hashmaps() {
     println!("collect_scores after rebuilding with doubling: {:?}", collect_scores);
 }
 
+fn read_file(path: &str) -> Result<String, std::io::Error> {
+    let mut s = String::new();
+    File::open(path)?
+        .read_to_string(&mut s)?;
+    Ok(s)
+}
+
 fn test_files() {
     if let Ok(mut f) = File::open("Cargo.toml") {
         let mut contents = String::new();
@@ -95,6 +102,12 @@ fn test_files() {
         panic!("Could not read file: {:?}", e);
     });
     println!("successfully opened Cargo.toml with unwrap_or_else: {:?}, contents {} bytes:\n{}\n----------", f, len, contents);
+
+    // using the '?' operator
+    match read_file("Cargo.toml") {
+        Ok(s) => println!("Cargo.toml contents:\n{}\n-------------", s),
+        Err(e) => println!("Could not open Cargo.toml: {:?}", e)
+    }
 }
 
 fn main() {