Convert Swift Errors to Optional Values

Written by Team Kodeco

When working with errors in Swift, sometimes it may be useful to convert an error to an optional value instead of handling it explicitly with a do-catch statement or propagating it using a throwing function. This can be useful when the error represents a failure that can be ignored or handled in some other way.

One way to convert errors to optional values is by using the try? operator. This operator attempts to evaluate a given expression and returns an optional containing the result if the expression completes without throwing an error. If an error is thrown, nil is returned instead.

Here’s an example of using the try? operator to convert the result of a throwing function to an optional:

import Foundation

func loadData(from url: URL) throws -> Data {
  // load data from url
  return Data()
}

let data: Data? = try? loadData(from: URL(string: "https://www.kodeco.com")!)

In this example, the loadData(from:) function can throw an error if it’s unable to load data from the specified URL. The try? operator is used to convert the result of the function to an optional, so that the calling code can handle the case where data isn’t successfully loaded.

Another way to convert errors to optional values is by using the try! operator. This operator attempts to evaluate a given expression and returns the result if the expression completes without throwing an error. If an error is thrown, the program will be terminated with a runtime error.

Here’s an example of using the try! operator to convert the result of a throwing function to a non-optional:

let data = try! loadData(from: URL(string: "https://www.kodeco.com")!)

In this example, the loadData(from:) function can throw an error if it’s unable to load data from the specified URL. The try! operator is used to convert the result of the function to a non-optional, so that the calling code can handle the case where data isn’t successfully loaded.

It’s important to note that converting errors to optional values using try? or try! can make it more difficult to diagnose and fix bugs that occur in your code. If the function can throw an error but the calling code doesn’t handle it properly, the error may go unnoticed, leading to unexpected behavior or crashes. It’s usually better to use do-catch statement or a throwing function to handle errors explicitly.