Rust Programming: Recoverable Errors

In Rust, recoverable errors are those that can be handled and the program can continue running. Recoverable errors are typically handled using the Result enum.

The Result enum has two variants: Ok and Err. The Ok variant represents a successful operation and contains the value that was produced by the operation. The Err variant represents a failed operation and contains an error value that describes the failure.

Functions that can fail typically return a Result value. This allows the caller of the function to handle the error in a way that makes sense for their program.

For example, the following function tries to open a file:

Rust

use std::fs::File;

fn open_file(filename: &str) -> Result<File, std::io::Error> {
    File::open(filename)
}

This function can fail if the file does not exist, if the caller does not have permission to open the file, or for some other reason. If the function fails, it will return an Err variant containing an error value.

The following code shows how to call the open_file() function and handle the error:

Rust

let file_result = open_file("my_file.txt");

match file_result {
    Ok(file) => {
        // The file was opened successfully.
        // Use the file here.
    }
    Err(error) => {
        // The file failed to open.
        // Handle the error here.
    }
}

The match expression will match the Result value returned by the open_file() function. If the value is an Ok variant, the code in the first arm of the match expression will be executed. If the value is an Err variant, the code in the second arm of the match expression will be executed.

In the example above, the code in the first arm of the match expression will use the file handle to read or write to the file. The code in the second arm of the match expression will handle the error in a way that makes sense for the program. For example, the program could log the error, display a message to the user, or try to open a different file.