Swift

Swift brings us classes and structs which both can look quite similar. When should you use a struct and when should you go for a class? Cannot assign to property: function call returns immutable value You're probably not the first to just simply fallback to changing your type to a ...

Once you get started with Combine you'll quickly run into error handling issues. Each Combine stream receives either a value or an error and unlike with frameworks like RxSwift you need to be specific about the expected error type. To be prepared on those cases I'll go over the options ...

An Array and a Set seem to be quite the same in the beginning. They're both collection types and have quite a lot of similarities. Still, we're often tempted to use Arrays instead of Sets. While this does not have to be a problem it could definitely be better to ...

A brand new Xcode refactoring engine was introduced in Xcode 9. Although this is quite a few Xcode versions ago it is still a quite unknown functionality for a lot of us. You might have read my blog post on command-click options but do you know how to extract methods ...

The UIKeyCommand class allows you to add keyboard shortcuts to your app. Although they might seem useful for iPad only, there are reasons to add this to your iPhone app as well. They're easy to set up and they work in the simulator! After I wrote Shortcuts essentials in Xcode ...

Combine debugging can be hard with long stack traces which don't help at all. Asynchronous callbacks follow up on each other rapidly and easily make it hard to find the root cause of an issue. It's next to the big learning curve one of the most common reasons to not ...

A Custom Combine Publisher can add missing functionalities to UIKit elements you use every day. A lot of boilerplate code can be removed and implementations can be simplified. A simple example is responding to UIControl events. The standard library comes with a few great extensions to, for example, decode JSON ...

Dynamic member lookup has been introduced in Swift 4.2 with SE-195 and already allowed some pretty nice solutions to for example implement JSON parsing. Just like the @propertyWrapper keyword as discussed in last weeks blog post, it can be used with a @ keyword: @dynamicMemberLookup. As quoted from the proposal, ...

An NSBatchDeleteRequest can be used to efficiently delete a batch of entries from a Core Data SQLite persistent store. It runs faster than deleting Core Data entities yourself on a managed object context as they operate at the SQL level in the persistent store itself. Its usage, however, is a ...

Weak self and unowned self in Swift for many of us are hard to understand. Although Automatic Reference Counting (ARC) solved a lot for us already, we still need to manage references when we're not working with value types. When writing Swift code we often run into situation while writing ...

A typealias in Swift is literally an alias for an existing type. Simple, isn't it? They can be useful in making your code a bit more readable. By using them in a smart way they can be really useful in your codebase. Declaring a typealias A typealias can be declared ...

@unknown default has been introduced in Swift 5 with SE-0192. It's a new addition to the way we can work with Swift enums and helps us to prepare for future changes. After updating your project to Swift 5 you might end up with a new warning in Xcode 10.2: Switch ...