TIP : Singleton about typescript-book HOT 5 CLOSED

I would also suggest considering showing a more traditional OOP singleton implementation, seen in languages such as C++, which I believe a lot of developers might find easier to understand.

class State {
    constructor(protected count = 0){

    }

    getCount(){
        return this.count;
    }
}

class ApplicationState {
    static state;
    static get(){
        if(!ApplicationState.state){
            ApplicationState.state = new State();
        }
        return ApplicationState.state;
    }
}

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@thefabulousdev one of the goals of the singleton pattern is to prevent any mistaken duplicate instances. Your code doesn't prevent that as new State(1);new State(2) would be allowed.

Of course it can be messaged to do the right thing but I will probably stick with Ryan's answer.

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Whoops, I knew I had missed something, here's what I meant

class State {
    constructor(protected count = 0){

    }

    getCount(){
        return this.count;
    }
}

class ApplicationState {
    static state;
    constructor(){
        if(!ApplicationState.state){
            ApplicationState.state = new State();
        }
        return ApplicationState.state;
    }
}

var something = new ApplicationState();
var somethingElse = new ApplicationState();

console.log(something === somethingElse); // true

You can see it running here

But I'm fine with your outcome.

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But I'm fine with your outcome.

Thanks 🌹

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@thefabulousdev thanks. I've taken your feedback into account as well : https://basarat.gitbooks.io/typescript/content/docs/tips/singleton.html 🌹

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