Making a C library available in Swift using the Swift Package Manager Nov 7 2019

System libraries are typically defined using C, that means we need a way to make them available to Swift. In this post, we are going to explore how to use the Swift Package Manager to give us access to C libraries, be it system or user-defined.

Let’s start by talking about Swift modules.

*NOTE: check the following GitHub repositories for the code:

• Csqlite3 gives us access to sqlite3.h C system library.
• SQLiteTester a Swift package executable that uses the Csqlite3 module.
• SQLite3 a wrapper that provides a Swifty interface to the SQLite3 C library.
• SQLiteClient a Swift package executable to test SQLite3.

#Swift modules

Multithreading with pthreads in Swift Oct 29 2019

Long gone are the days when single process single thread was the norm. We now take multithreading for granted, we expect all our applications not to lockup when we interact with them. We expect them to handle multiple users at the same time, etcetera. In this post, I’ll explain what multithreading is and how to use threads (using pthreads) in Swift.

Before someone tells me that in 2009 GCD (Grand Central Dispatch) was introduced, I know. This post is aimed at anyone that wants to understand how multithreading works using threads. To use threads directly in Swift, we need to interoperate with C code. We need to go down to using pthreads directly. We’ll go from the basics of threads and then write a Server simulator using threads.

Creating a Launch Agent that provides an XPC service on macOS using Swift Oct 21 2019

Last week we discussed how to build XPC Services(the .xpc bundles) inside your macOS applications. This week we are going to explore how to provide XPC services that can be used from other applications or tools.

To make the XPC service available to other processes, we are going to create a launch agent. So let’s start by understanding how Launch Agents work.

* You can find the code for the Launch Agent in this GitHub repository

XPC Services on macOS apps using Swift Oct 17 2019

We have access to many Inter-Process-Communication(IPC) mechanisms in macOS. One of the newest is XPC¹. Before XPC a common way to use IPC, and provide services between processes, was through Sockets or Mach Messages (Using Mach Ports).

Nowadays, we are encouraged by Apple to use XPC in our applications and frameworks that provide services. Also, Apple, in their code, has updated many of its frameworks, daemons and applications to use XPC.

Using Kernel Queues (kqueue) notifications in Swift Oct 9 2019

Many components of macOS trace their roots back to BSD. One key aspect inherited from BSD is the Kernel Event Notification mechanism know as Kernel Queues (kqueues for short).

In the past, before kqueue(2)¹/ kevent(2)², when we wanted to track events related to a socket, or if a file descriptor changed, we used a polling mechanism to test for readiness/events (maybe using select(2) or poll(2)). This polling techniques were inefficient and got replaced by the more efficient kqueue API. Instead of continually polling, we can now be notified about events by the kernel. Also, mechanisms like select(2) and poll(2) were restricted to work with file descriptors. kqueue increases the range of operating systems events to monitor not only for file descriptors but also elements like signals, timers, network devices, etc.

Understanding the RunLoop model by creating a basic shell Oct 1 2019

When we find ourselves listening for events, reacting to those events, and then going back to listening for more events, we have ourselves an Event-Loop. Having an event-loop is a common scenario. So common that Apple decided to provide us with a model to handle event-loops consistently. In this post, we are going to explore how RunLoops work and use them to build basic shell.

Let’s get started by creating a program that makes use of an event-loop.

Using BSD Sockets in Swift Sep 24 2019

Apple provides many useful network frameworks. Network.framework (you can check my previous article on Network.framework if you want to see an example) is the latest. But sometimes we need to go deeper, and the abstractions might get in the way. In this post, we are going to see how to use BSD sockets directly in Swift.

Using BSD sockets means interfacing with C from Swift. Let’s first have a look at some concepts and tips that will help us with using sockets.

Understanding Objective-C and Swift interoperability Sep 16 2019

There are many reasons to use more than one programming language in a project. In some cases, a lot of work has gone into building a framework (years maybe). Rewriting the whole framework to have the codebase in the same programming language, might not be the best use of resources. You can see this in macOS between the two main programming languages, Swift and Objective-C (three counting C). In this post, I’ll show how to use Swift code in Objective-C, and how to use Objective-C code in Swift. We are going to explore how the interoperability occurs by building the code manually to get a better understanding.

Building a server-client application using Apple's Network Framework Sep 10 2019

Apple’s network APIs are many, the older APIs are well documented, and you’ll find lots of examples. Not so much about the new Network framework. One factor might be that the name is not that search-friendly. In this post, I’ll explain how to use the NWFramework by creating a basic TCP server-client application.

The server will work as an echo, any message received will be sent back to the client. The client will allow us to send messages to the server and display the server response.

Understanding a few concepts of macOS applications by building an agent-based (menu bar) app Sep 3 2019

With advances in the frameworks and tools we use to develop software, creating a new app seems like magic. We just click a few buttons, and everything is created for us. I enjoy magic, but I think that sometimes we end up being Framework “users” without any real understanding of what is happening. In this post, I’ll explain a few concepts of how macOS apps work, so hopefully, we understand the ecosystem better.