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When developing iOS applications with Xcode, it’s essential to understand the difference between “Target Dependencies” and “Link Binary with Libraries.” These two options found in the Build Phases settings of a target play vital roles in defining how your app interacts with external code. In this article, we’ll discuss what these options do and how they are different. Understanding Targets Before we delve into the differences, let’s first understand what a ‘Target’ is in Xcode. A target specifies a set of build configurations which define how to build a product in Xcode. It could be an app, a framework, or a unit test bundle. Each target contains information about how to build the product, including build settings, build phases, and the product’s dependencies. ...

In this post we will learn how to build a Swift Package using a GitHub Codespace. I did this recently as an experiment. It was easier than expected. The codespace was quick to build and test on too. It could be a useful tool when you have a poor local environment, e.g. an aging Intel MacBook. That said, there’s limitations too. What are Codespaces Github codespaces are development environments in the cloud. They allow you to develop from your browser. Opening a codespace displays a VS Code IDE. You can install libraries, dependencies and tools. You can run any code you write in the terminal. ...

In this blog post, we explore the concept of subjects in the Combine framework. We’ll look at two types provided by Apple: CurrentValueSubject and PassthroughSubject. We’ll explore their differences and when to use them. What are Subjects? Subject is a type of publisher in the Combine framework that adheres to the Subject protocol. It has a .send(_:) method that allows developers to send specific values to a subscriber. Subjects put values into a stream. This is useful when you need to mix imperative code with Combine. ...

Let’s learn how to navigate a UIPageViewController using a UISegmentedControl in iOS. The UIPageViewController provides a way to display pages of content, where each page is managed by its own view controller. The UISegmentedControl displays segments and allows users to switch between them. We’ll begin by setting up the UISegmentedControl and UIPageViewController, then move on to connecting them by programmatically navigating the UIPageViewController based on the selection in the UISegmentedControl. ...

When writing unit tests for Swift networking code that uses URLSession we don’t want to perform real network requests. We want to mock responses so that our unit tests remain fast, predictable and independent. Mocking responses from URLSession can be done by wrapping it in a protocol and creating a mock session when testing. But an alternative way is using URLProtocol. What is URLProtocol? URLProtocol is a class that allows you to intercept and handle network requests, giving you the ability to implement features such as caching, redirects, or authentication. When it comes to testing, it gives the ability to intercept requests and return mocked responses, as well as spy on the request that was sent. ...

Apple’s Combine framework has two operators called .share() and .makeConnectable(). They are extremely useful but often misunderstood. Both help us avoid unnecessary processing. .share(), as the name suggests, helps us share a subscription. .makeConnectable() helps control when publishers emit events. Working with Multiple Subscribers Imagine you have a simple view with a button and two labels. When a user taps the button, the text on the two labels will be updated. ...

Future Combine provides the Future publisher class to model a single asynchronous event. The Future acts like a promise. It can either fulfil its promise or fail to fulfil its promise. Those familiar with promises from frameworks like PromiseKit might liken Future to a promise. The added benefit of using Future is that it is a publisher, so you can use them with operators and subscribers and easily integrate them into combine data streams. ...

In this post, we will look at the Publisher protocol in Swift’s Combine framework. What is it? Why is it? 🤔 Why does Publisher exist? Combine is swift’s reactive programming framework. A reactive programming framework works with streams of data emitted over time. Combine needs something that can model a data stream. This is the role of the Publisher protocol. The protocol looks like this: protocol Publisher<Output, Failure> For the protocol to model a data stream it needs to allow for three things: ...

So you have a UISearchBar like the one shown below. A user typing into a search bar is an ideal input data stream for Combine. Ideally, we’d access a string publisher based on user input like so. let searchBar = UISearchBar() let searchText = searchBar.textPublisher Alas, it does not exist. I also tried performing Key-Value Observing with Combine on the searchBar or its text field. searchBar.publisher(for: \.text) searchBar.searchTextField.publisher(for: \.text) It compiles but emits no events. ...

Data Streams Reactive programming is programming with asynchronous data streams This is useful because anything can be represented as a stream of data, including user input, network responses, and even internal program state. By treating everything as a stream, it becomes possible to use a single set of abstractions to handle all types of data, making it simpler to reason about and manage the flow of data through an application. ...