Example on error handling and checking error types

errors/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "errors"
+version = "0.1.0"
+authors = ["laurens <miers132@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

errors/src/main.rs

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+use std::fs;
+use std::fs::File;
+use std::io::ErrorKind;
+use std::io;
+use std::io::Read;
+use std::error::Error;
+
+fn open_and_close_with_match(path: &String) -> File {
+    // Big block of code with match-expressions for nothing really
+    let f = match File::open(path) {
+        Ok(file) => file,
+        Err(error) => match error.kind() {
+            ErrorKind::NotFound => match File::create(path) {
+                Ok(fc) => fc,
+                Err(e) => panic!("Problem creating the file: {:?}", e),
+            },
+            other_error => panic!("Problem opening the file: {:?}", other_error),
+        },
+    };
+
+    return f;
+}
+
+fn open_and_close_without_match(path: &String) -> File {
+    let f = File::open(path).unwrap_or_else(|error| {
+        if error.kind() == ErrorKind::NotFound {
+            File::create(path).unwrap_or_else(|error| {
+                panic!("Failed to create file {:?}", error);
+            })
+        } else {
+            panic!("Problem opening file {:?}", error);
+        }
+    });
+
+    return f;
+}
+
+fn read_username_from_file(path: &String) -> Result<String, io::Error> {
+    let mut f = File::open(path)?;
+    let mut s = String::new();
+    f.read_to_string(&mut s)?;
+    Ok(s)
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let path = "hello.txt".to_string();
+
+    println!("Open/create file {}", path);
+    open_and_close_with_match(&path);
+
+    // If we get here, the file surely exists
+    println!("Remove file {}", path);
+    fs::remove_file(&path).expect("Failed to remove file");
+
+    println!("Open/create file {}", path);
+    open_and_close_without_match(&path);
+
+    // If we get here, the file surely exists
+    println!("Remove file {}", path);
+    fs::remove_file(&path).expect("Failed to remove file");
+
+    let username = read_username_from_file(&path).expect("Could not read username from file");
+
+    println!("username: {}", username);
+
+    // Returning error out of main
+    let _f = File::open("hello.txt")?;
+    fs::remove_file(&path).expect("Failed to remove file");
+
+    Ok(())
+}