What is the method for handling errors in Rust?

2 years ago
Liam
2 minutes

In Rust, the Result type is a method used to handle operations that may result in an error. The definition of the Result type is as follows:

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

In which, T represents the type of value returned when the operation is successful, and E represents the type of error returned when the operation fails.

There are two main ways to handle errors using the Result type: by using match expressions or by using the ? operator.

  1. game
fn read_file() -> Result<String, io::Error> {
    let file = File::open("file.txt");

    match file {
        Ok(mut f) => {
            let mut contents = String::new();
            f.read_to_string(&mut contents)?;
            Ok(contents)
        }
        Err(e) => Err(e),
    }
}

In the above example, the read_file function tries to open a file and read its contents as a string. If both the file opening and reading operations are successful, it returns Ok(contents); if either the file opening or reading operation fails, it returns Err(e).

  1. Can you please rephrase this sentence in English?
fn read_file() -> Result<String, io::Error> {
    let mut file = File::open("file.txt")?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;
    Ok(contents)
}

In the example above, the ? operator can be used to replace the Ok and Err branches in the match expression. If the operation is successful, continue executing the subsequent statements; if the operation fails, return the error directly.

The prerequisite for using the “?” operator is that the return type of the function must be a Result type, and it must be used to handle errors at every possible error-generating point within the function body.

These are two common methods for handling errors in Rust, developers can choose the appropriate method for error handling based on their specific needs.

bannerAds