Sharing a state using Singleton

There are two questions that interviewers love to ask:

• “How do we create a Singleton?”
• “Is it good to have singletons in our app?”

The first question is technical, but the second one is tricky.

Let’s start with the definition of a Singleton.

What is a Singleton?

In the Singleton design pattern, there is only one instance of a class that can be globally accessed through a static property. It is often used to manage shared resources or states in a program where multiple instances could cause issues with synchronization or consistency. To implement a Singleton, a class typically has a private constructor and a static method or property that returns the single instance of the class.

In Swift, it is simple to create a Singleton. We use a static property for that task:

final class MySingleton {    static let shared = MySingleton()
    private init(...