Remote configuration is a common practice in almost every app I have worked on. Sometimes these configurations can be large and the implications of a configuration change can be far-reaching while other times a configuration is used to change the number of items shown in a list, or to enable or disable certain features. You can even use remote configuration to set up your networking layer. For example by setting certain headers on a request, providing endpoints for your remote data, and more. In this week's post I will not go into detail about every possible use case that you...

A common use of a Core Data store is to cache data from a remote resource locally to support offline functionality of an app. There are multiple ways to implement a caching mechanism and many of them don't involve Core Data. For example, you could simply fetch a JSON file from a server and store the contents of that JSON file on disk. A downside of fetching a full data set every time is that you risk using a lot of bandwidth, especially if your data set is large, or if your data set is expected to grow over time....

In the past two weeks I have introduced you to Combine and I've shown you in detail how Publishers and Subscribers work in Combine. This week I want to take a more practical route and explore Combine in a real-world setting. A while ago, I published a post that explained how you can architect and build a networking layer in Swift without any third-party dependencies. If you haven't seen that post before, and want to be able to properly follow along with this post, I recommend that you skim over it and examine the end result of that post. This...

In my previous post about Combine, I introduced you to Functional Reactive Programming (FRP) and I've shown you can subscribe to Combine publishers using the sink(receiveCompletion:receiveValue:) method. I also showed you how you can transform the output of publishers using some of its built-in functions like map and collect. This week I want to focus more on how Combine publishers and subscribers work under the hood. By the end of today's post, you should have a clear picture of what Combine's core components are, and how they relate to each other. The topics covered in today's post are the following:...

Swift grants developers the ability to shadow certain types with an alternative name using the typealias keyword. We can use this feature to create tuples and closures that look like types, or we can use them to provide alternative names for existing objects. In this post, we'll look at five ways in which typealiases can help you write cleaner and better code. 1. Improving readability with type aliases Perhaps this is the most obvious yet also somewhat underused way to use a typealias. When you have a type in your code that is very long or deeply nested, you could...

One of the topics that I could write dozens of posts on is networking. Making calls to a remote API to retrieve or persist data is something that is a key feature in many apps that are currently in the App Store. Some apps make extensive use of the network while others only need the network to retrieve data periodically. No matter how extensively your app uses the network, the patterns for using the network in a clean and appropriate manner are often (roughly) the same. I have written several posts on networking in the past: Architecting a robust networking...

Both networking and protocols are topics that I could write dozens of posts on, and I would still have more ideas and examples left in my head. In today's article, I would like to combine the topics of networking and protocols and explain how you can design a robust networking layer for your app, that's 100% testable and mockable because everything down to the URLRequest is abstracted behind a protocol. Defining our goals Any time you're getting ready to write code, you should define your goals first. What are you writing? What problems are you trying to solve? This is...

Whenever we write code, we want our code to be well-designed. We want it to be flexible, elegant and safe. We want to make sure that Swift’s type system and the compiler catch as many of our mistakes as possible. It’s especially interesting how Swift’s type system can help us avoid obvious errors. For example, Swift won’t allow you to assign an Int to a String property like this: var anInt = 10 anInt = "Hello, World!" The Swift compiler would show you an error that explains that you can’t assign a String to an Int and you’d understand this....

Developers often need to store data on behalf of their users. Sometimes it’s a small amount simple data, other times it’s a lot of complex data. Maybe it’s highly sensitive data or maybe it’s less sensitive or even publicly available data. Choosing where to store this data is often not trivial, especially if you might be unaware of the options that are available to you, or the security considerations you need to keep in mind. In this week’s blog post I will show you several storage options that are available to you as an iOS developer, and I'll explain the...

Apps send and receive data all the time. Some apps mostly read data from the network, others are more focussed on sending data to servers. Depending on your needs, you might need to be able to send data to a server as quickly as possible, or maybe you need to receive new data as soon as it’s available from a server. Every app has different needs and several mechanisms exist to streamline network communication. In this post week’s blog post, I will focus on one specific use of networking in apps. We’ll look at using web sockets to receive data...