Let’s assume that you’re doing an application which shows your users pretty pictures of seasons. You contact your backend folks and they tell you that the world is simple, there are only three seasons:

enum Season: String, Decodable {
    case spring, summer, autumn
}

Most apps these days have a sequence of screens that gather information from the user, like a registration flow, a form of some kind. The data from each step is typically combined into a single data structure. For example, let’s say we want the name, age, and the password to authenticate the user.

Codable is a great protocol available in Swift. It makes it possible to create a type safe JSON representations of structures used within our application with zero boilerplate.

struct Person: Codable {
    let name: String
    let email: String
    let age: Int
}

Once the structure conforms to Codable everything works out of the box. There’s a nice way to test those structures and make sure that everything gets the exact JSON format that we aligned with backend.

Testing code often demands faking the “real world”. IoC plays a huge role in here where you flip the dependency from a concrete implementation to an interface.

This technique is very useful when you want to abstract away third-party code (think UserDefaults), but there are instances where this is not enough. That’s the case when working with the camera.

On iOS, to use the camera, one has to use the machinery that comes with AVFoundation.

The way I was introduced to the Design Patterns lead me to think that those clever and neat solutions were meant to be used just in big softwares solutions. I never considered using them into the small pieces of software. What do I mean by that? Please, read on.

The Builder Pattern if defined as follows:

Separate the construction of a complex object from its representation so that the same construction process can create different representations.

Swift 1.2 introduced us with @noescape attribute. It’s a very important feature, when we want to make our code more cleaner and stricter. Using it properly at 3am will prevent many unwanted retain cycles.

While digging into release notes we can see a bunch of clever words:

A new @noescape attribute may be used on closure parameters to functions. This indicates that the parameter is only ever called (or passed as an @noescape parameter in a call), which means that it cannot outlive the lifetime of the call. This enables some minor performance optimizations, but more importantly disables the self. requirement in closure arguments.

Swift like objC allow us to mix it with other languages, unfotunately when it comes to Swift we can only choose between our good old friend objC or ANIS C, as there is still lack of C++ support. Basically using function pointers allows us to call C functions inside Swift. Swift will automatically convert methods included in Bridge Header into Swift equivalents:

Today Bluetooth Low Energy can be found in many cool applications, it can be used from simple data exchange to payment terminals and the more popular usage with iBeacons. But what if we want to build something funny with it? Like some simple game not even realtime, it may be even turn based game. Imagine you do not need to go through this long setup, waiting for server players to be ready etc.

Everyone knows that building good multiplayer game is hard, multiplayer itself is hard… But here I want to show you my small proof of concept of working bluetooth low enery multiplayer game.

Swift is out there for about a year and it’s a great programming language. I think that almost every iOS/OSX developer out there has already written couple of things in Swift (if you haven’t, go ahead and try, you won’t regret it, I promise). Although, we have many years of libs and frameworks built using Objective-C and sooner or later a project may have both Swift and Objective-C working together.

Gone are the days where there was just one iPhone for developers as a target. Now we have to support multiple devices with different screen sizes. Fortunately, we have autolayout, which solves a part of this design equation, the other part is solved with UITraitCollection. Trait collection object has two size classes: horizontal and vertical. Each of these classes has three possible values: compact, regular or any. The current device+orientation can be described as a combination of the sizes.