public/subjects/unwrap_or_expect

unwrap_or_expect

Instructions

Create a function named fetch_data which has two arguments:

• server: Which is a Result having the server url or an error message inside.
• security_level: Which is an enum defining the behavior of the function in case of errors.

The security_level will work as follow:

• Unknown: The function panics without printing any custom message.
• High: The function panics and prints the error message ERROR: program stops.
• Medium: The function returns the string WARNING: check the server.
• Low: The function returns the string Not found: [SERVER_URL].
• BlockServer: The function will panic only if the Result value is Ok and the error message will be the string contained in Ok.

To return from fetch_data you must use expect, unwrap_or, unwrap_err, unwrap and unwrap_or_else.

Expected Functions

pub enum Security {
	Unknown,
	High,
	Medium,
	Low,
	BlockServer,
}

pub fn fetch_data(server: Result<String, String>, security_level: Security) -> String {

}

Usage

Here is a program to test your function:

use unwrap_or_expect::*;

fn main() {
    println!("{}", fetch_data(Ok("server1.com".to_string()), Security::Medium));
    println!("{}", fetch_data(Err(String::new()), Security::Medium));
    println!("{}", fetch_data(Err("server2.com".to_string()), Security::Low));

    // Panics with no custom message
    // fetch_data(Err("ERROR CRITICAL".to_string()), Security::Unknown);

    // Panics with the message "ERROR: program stops"
    // fetch_data(Err(String::new()), Security::High);

    // Panics with the message "malicious_server.com"
    // fetch_data(Ok("malicious_server.com".to_string()), Security::BlockServer);
}

And its output:

$ cargo run
server1.com
WARNING: check the server
Not found: server2.com
$

Notions

• Error Handling
• Unwrap keywords