finish chapter 9

1 files changed, 62 insertions, 0 deletions

diff --git a/rust/theBook/chapter-9-error-handling/result/src/main.rs b/rust/theBook/chapter-9-error-handling/result/src/main.rs
new file mode 100644
index 0000000..265250c
--- /dev/null
+++ b/rust/theBook/chapter-9-error-handling/result/src/main.rs
@@ -0,0 +1,62 @@
+use std::fs::{Self,File};
+use std::io::{Self, Read, ErrorKind};
+
+fn main() {
+    let greeting_file_result = File::open("hello.txt");
+
+    let greeting_file = match greeting_file_result {
+        Ok(file) => file,
+        Err(error) => match error.kind() {
+            ErrorKind::NotFound => match File::create("hello.txt") {
+                Ok(fc) => fc,
+                Err(e) => panic!("problem opening file {:?}",e),
+            },
+            other_error => {
+                panic!("problem opening file {:?}",other_error);
+            }
+        },
+    };
+
+    // or use unwrap, it will return value or panic just like match
+    // let greeting_file = File::open("hello.txt").unwrap();
+}
+
+// functions to read username from file
+// each one is a shorter solution of its previous one.
+fn read_username_from_file() -> Result<String, io::Error> {
+    let username_file_result = File::open("hello.txt");
+
+    let username_file = match username_file_result {
+        Ok(file) => file,
+        Err(e) =>   return Err(e),
+    };
+
+    let mut username = String::new();
+
+    match username_file.read_to_string(&mut username) {
+        Ok(_) => Ok(username),
+        Err(e) => Err(e),
+    }
+}
+
+// ? is like match, but shorter
+// return content of Ok() if true, or return Err() from whole function
+fn read_username_from_file_short() -> Result<String, io::Error> {
+    let mut username_file = File::open("hello.txt")?;
+
+    let mut username = String::new();
+
+    username_file.read_to_string(&mut username)?;
+    Ok(username)
+}
+
+fn read_username_from_file_even_short() -> Result<String, io::Error> {
+    let mut username = String::new();
+
+    File::open("hello.txt")?.read_to_string(&mut username)?;
+    Ok(username)
+}
+
+fn read_username_from_file_shortest() -> Result<String, io::Error> {
+    fs::read_to_string("hello.txt")
+}