Double Dispatch in Swift

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Before we start

Difficulty: Beginner | Easy | Normal | Challenging

This article has been developed using Xcode 11.5, and Swift 5.2.4

Prerequisites

• You will be expected to be aware how to make a Single View Application in Swift.
• It would be useful to understand something about Polymorphism) in Swift.
• You should be aware of the types of method dispatch in Swift

Terminology:

Double Dispatch: A mechanism that dispatches a function call to different concrete functions depending on the runtime types of two objects involved in the call

Polymorphism: This is the ability of an object to take on many forms, with a common using being a parent class reference to refer to a child class object

Introduction

Double Dispatch is a technique used to invoke an overload method where parameters vary among an inheritance hierarchy.

The Visitor Pattern is built upon the double dispatch principle. So what is it?

Double Dispatch