Swift Initialization

A Simple(ish) guide

Steven Curtis

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Initialization is hugely important in any modern language. This is not a full guide (Apple have provided a long guide, which is referenced below) but rather a shorter example-laden walk through initialization for Swift.

Before we start

Difficulty: Beginner | Easy | Normal | Challenging

This article has been developed using Xcode 12.2, and Swift 5.3

Prerequisites:

  • Some understanding of OO concepts
  • Some idea of Structs and Classes in Swift

Terminology

Initializers: Called to create a new instance of a type, be it a struct, enum or a class.

Initializer delegation: Where an initializer calls other initializers to perform part of an instances initialization.

Initializers

Initializers for structs — the default initializer

An initializer can easily be created within a struct (note that the internal and external names are usually the same in an initializer)

However, Swift has a memberwize initializer (so long as you do not provide a single initializer).

We can also call another initializer to perform the initialization (or part of it). This is called initializer delegation.

Designated initializers for a simple class

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