Swift Posts

It usually doesn’t take beginning macOS/iOS developers long to discover NotificationCenter and see it as the solution to every single problem of passing data around to different controllers. And NotificationCenter is great, but it has some downsides. Notably, it is very easy to introduce retain cycles (and memory leaks) unless you are very careful to track and free the listener when the object is released. This has bitten me on several occasions. In general, excessive use of NotificationCenter ends up creating a difficult to maintain app where it is not entirely clear what is responding to what and where.

Object oriented programming is great, but sometimes things don’t fit neatly into a superclass/subclass hierarchy. You may have a piece of code that would be needed in several contexts, but for technical reasons beyond your control you cannot merge them into a single hierarchy. Some languages have the concept of multiple inheritence, where a subclass can specifically inherit from several parents. But this has it’s own set of problems. Many other languages, however, solve this through the use of traits or mixins. These allow us to have a set of methods that are basically copied into the object at compile time. This way they can be used anywhere they are needed. Swift doesn’t have the concept of mixins or traits per se. But, starting with Swift 3, you can get very equivalent functionality using protocol default implementations.

Somewhat related to my previous post about responder chains, sometimes it is useful to be able to debug what all is in the responder chain at any given time. As a good rule of thumb, all ancestor views of a view are in that view’s responder chain, as well as (usually) the related controllers.

The responder chain is one of those parts of macOS and iOS development that may seem a little strange if you have not done any GUI programming before. Briefly, a responder chain is a hierarichy of objects that can respond to events. So, for example, a click or a tap might be passed up the responder chain until something responds to the action. But, the responder chain is more than just UI events. We can pass our own custom events up the responder chain as well!

Siesta is a framework for Swift that dramatically simplifies working with RESTful APIs. And like many things in Swift, it is natively built around asynchronous execution. It may fire any number of requests back, and they may complete in any order that is undefined. But sometimes, you need to execute things in a specific order. Like when the result of one call will change subsequent calls. A classic example of this is an API where you might need to create a folder first, then upload files into the folder you created. So the folder creation needs to happen first, then the file uploads can happen after.

Launched two new pieces of open source code in the last couple of months. PlayerControls PlayerControls is a macOS Cocoa framework that creates a View containing playback controls for media like videos or sounds. It is written in pure Swift 4 and has no dependencies. SearchParser SearchParser is a parser that converts a freeform query into an intermediate object, that can then be converted to query many backends (SQL, ElasticSearch, etc). It includes translators for SQL (using PDO) and Laravel Eloquent ORM. It supports a faceted language search as commonly found on many sites across the web. It is written in modern PHP. Both are licensed under the MIT license. Go check them out on Github.