Typed Errors in Swift with the Result Type

The Result type has been around for a while, there have been many variations on it on community maintained frameworks such as Alamofire, and RxSwift, there’s even a μframework called Result before Swift 5 introduced the Result type on SE-0235.

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Gracefully handling scenarios with two outcomes is something we as developers would usually work on. The Result type has been added for handling these two outcomes, a Success or a Failure.

This is where the Result type comes in.

Use Result whenever an operation has the possibility of failure. ~ Rob Rix

The Result type is basically just an enum that contains two cases

Before coding for a scenario like this would normally require you to use a do try catch block, but sometimes a concrete Error data type will be more advantageous, and what is Swift if not for its powerful type system.

Take an email TextField for example, normally we do have the following checks before we store the data.

• Is the string is empty?
• Does the string have white spaces?
• Is the string a valid email address?

First, let’s create an Error type which contains the rules above.

Then let’s create a method that will have to validate the TextFields’s text.

Note: This example is overkill for email validation, chill… ヽ(´▽`)/

Using this would be as simple as using a switch statement

You can also implement this using a do try catch statement. To do that you can use the .get() method of Swift’s Result which returns the Success value or throws an Error if the Result evaluates into a Failure.

Long story short with Result, errors are typed, concise, and you don’t need to have a catch-all block like the do try catch statement but the beauty of this is if ever you want to use thedo try catch the .get() method is already available for use.

If you’re reading this, then you’ve reached the end. Cheers! 🍻

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