Error handline

• Panic
• Option
• Result

1. Panic Simplest way to handle errors

What happens when a panic is encountered?

• Failure message is printed
• Program unwinds and cleans up the Stack
• Program quits

Should only be used when program comes to an unrecoverable state

Syntax:-

panic!("Farewell");

let v = vec![0, 1, 2, 3];
println!("{}", v[6]); // This will cause a panic

1. Option enum
   • Manages the possibility of none existent values
   • Type T is generic and associated with the Some variant.
   • None indicates that no element was found.
   • Some means that an element of type T was found

Syntax:-

enum Option<T> {
    None,
    Some(T),
}

1. Result enum
   • Used for input/output operations (I/O)
   • Parsing strings
   • File access
   • Data validation - Best for expected failures

Syntax:-

fn main() {
    enum Result<T, E> {
        Ok(T),
        Err(E),
    }
}

• Used for recoverable errors that are more common
• The Ok(T) variant represents a success and contains a value
• The Err(E) variant represents an error

Unwrap and Expect

• Helper methods Of the Result type
• Unwrap returns the value inside the Ok variant. Returns a panic! macro for the Err variant.
• Expect returns a value or called the panic! macro with a detailed error message

fn main() {
    // ok
    File::open("hello.txt").unwrap();

    // Err
    File::open("hello.txt").expect("Failed to open hello.txt");
}

The ? operator

• Similar to a match statement
• For Result type:
  • Unwraps the value if 0k variant
  • Returns an error if Err variant.
• For Option type:
  • Returns a value is with the Some variant
  • Returns nothing for the None variant