Swift

Associated types in Swift work closely together with protocols. You can literally see them as an associated type of a protocol: they are family from the moment you put them together. Obviously, it's a bit more complicated to explain how associated types work but once you get the hang of ...

The Result enum is available since Swift 5 and allows us to define a success and failure case. The type is useful for defining the result of a failable operation in which we want to define both the value and error output type. The standard Swift library adds more functionality ...

Constraints in Core Data are part of an entity configuration. Settings like the entity name and Spotlight display name might be easy to understand while constraints are a bit less known. However, they can be super useful to maintain a unique set of data. Constraints can take away the need ...

An NSManagedObject lifecycle goes from insertion and updates until deletion in the end. All those events come with their own common related modifications and can be used in many different ways. Managing state in Core Data from within the NSManagedObject class itself is a great way to keep logic centralized ...

Try catch in Swift combined with throwing errors make it possible to nicely handle any failures in your code. A method can be defined as throwing which basically means that if anything goes wrong, it can throw an error. To catch this error, we need to implement a so-called do-catch ...

Diffable Data Sources were introduced at WWDC 2019 as a replacement for UICollectionViewDataSource and UITableViewDataSource. The API is available on iOS 13 and up and makes it easy to set up lists of data in which changes are managed through so-called snapshots. The Core Data team added new delegate methods ...

Diffable Data Sources were introduced at WWDC 2019 and are available since iOS 13. They're a replacement of the good old UICollectionViewDataSource and UITableViewDataSource protocols and make it easier to migrate changes in your data views. Diffable Data Sources come with a few benefits over using the classic data source ...

WWDC 2017 introduced a new concept available from iOS 11 which is persistent history tracking. It's Apple's answer for merging changes that come from several targets like app extensions. Whenever you change something in your Core Data database from your Share Extension, a transaction is written which can be merged ...

Write-Ahead Logging is the default journaling mode for Core Data SQLite stores since iOS 7 and OS X Mavericks. Journaling in Core Data is best explained as the way data transactions are saved into the underlying SQLite store. The WAL mode is significantly faster in most scenarios compared to the ...

The target-action pattern is used in combination with user interface controls as a callback to a user event. Whenever a button is pressed on a target, its action will be called. The fact that the method is not defined close to the control definition is sometimes seen as a downside ...

ValueTransformers in Core Data are a powerful way of transforming values before they get inserted into the database and before they get read. They're set up in an abstract class which handles the value transformations from one representation to another. They're often used as a way to store values that ...

While writing methods in Swift you're often running into scenarios in which you sometimes want to ignore the return value while in other cases you want to know the return value. The @discardableResult attribute allows us to enable both cases without having to deal with annoying warnings or underscore replacements ...