How do you use the rust result?

2 years ago
Liam
2 minutes

The Result type in Rust is an enum used to handle the outcome of operations that may result in an error. It can have two potential values: Ok for a successful operation and Err for a failed operation, which also includes an error value.

The usage method of the Result type is as follows:

  1. Defining the return value of a function using the Result type: You can specify the return type of a function as Result in the function’s signature, where T is the type of the return value on success and E is the type for errors. For example, fn divide(x: f64, y: f64) -> Result
  2. Return the results using Ok and Err: In a function, you can use Ok(value) to signify a successful result, where value is the value returned upon success; use Err(error) to indicate a failed result, with error being the error value. For example, Ok(result) or Err(error)
  3. To handle the results of a Result type, you can use pattern matching with match expressions or if let expressions. By matching the different cases of Ok and Err, you can handle the operation’s results accordingly. For example:
let result = divide(10.0, 0.0);
match result {
    Ok(value) => println!("Result: {}", value),
    Err(error) => println!("Error: {}", error),
}

Alternatively, use the if let expression to handle specific cases.

if let Ok(value) = result {
    println!("Result: {}", value);
} else if let Err(error) = result {
    println!("Error: {}", error);
}

This allows for separate handling of successful and failed outcomes of the operation.

  1. Can you say that again in your own words?
  2. Can you rephrase this in your own words?
  3. Outcome
  4. Can you explain that in another way in English?
fn calculate(x: i32, y: i32) -> Result<i32, String> {
    let result = divide(x as f64, y as f64)?;
    Ok(result as i32)
}

If the divide function returns Err when called, the entire calculate function will also return Err, allowing for the error to be handled at the caller’s end.

These are basic methods using the Result type in Rust, which can be appropriately handled based on specific needs.

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