Variables, States, and Scope

[Andromedus]

Hi - first time post here so hello to everyone.  Enjoying Phaser so far!

I've got a basic game framework working using States.  I'm new to Javascript, coming from an AS3 background where I would use separate classes with variables local to each class.  In a similar way, I'm trying to work out how to define a variable which is local to a particular state.  

To put it another way, how/where would I define myVar, such that:

var state1 = {

    create: function(){
        //myVar used here
    },

    update: function(){
        //myVar used here too
    }
}

var state2 = {

    create: function(){
        //myVar not accessible here
    }
}

I realise that I could define myVar outside of both states, but then it would be global to all states.  In my case, myVar is actually an object which has a whole load of properties and display objects, so potentially a lot of stuff to persist across states without getting garbage collected when I change states.

Thanks in advance for any advice.

 

[Tom Atom]

Hi, you can do this:

var state1 = {

    create: function(){
        //myVar used here
        console.log(this.game.state.states["s2"].greet);
    },

    update: function(){
        //myVar used here too
    }
}

var state2 = {

    greet: "hello",

    create: function(){
        //myVar not accessible here
    }
}

game = new Phaser.Game(1080,600, Phaser.AUTO, 'game');

game.state.add('s1', state1);
game.state.add('s2', state2);
game.state.start('s1');

 In state1 you are accessing varibale from state2.

[Andromedus]

Thanks Tom.

So ... you're creating the 'greet' variable as a key/value pair of the state object.  That makes sense, and in that case I guess I could even just access it where I need it with 'state2.greet' (or 'this.greet' if I want to access it from within the same state), like this:

 

var state1 = {

    create: function(){
        
        console.log(state2.greet);
    },

    update: function(){
        
        console.log(state2.greet);
    }
}

var state2 = {

    greet: "hello",

    create: function(){
        console.log(this.greet);
    }
}

game = new Phaser.Game(1080,600, Phaser.AUTO, 'game');

game.state.add('s1', state1);
game.state.add('s2', state2);
game.state.start('s1');

 

Thanks, I'm beginning to get my head around this now.

 

 

[Tom Atom]

To be honest, I am not too experienced in pure Javascript as I use Typescript (+ Visual Studio 2015 as IDE). In it you can declare object variables as static or instance related like in Java / C# languages. You can also simlpy mark them as public/protected/private.

[Andromedus]

Sounds good.  I decided to start off with pure JS so that I could follow the examples and tutorials, but I may well switch to typescript later on.  Cheers.

[samme]

Do you just need state-local variables?

var state1 = {
    create: function(){
        this.thing;
    },
    update: function(){
        this.thing; // same thing
    }
}

var state2 = {
    create: function(){
        this.thing; // totally different thing
    }
}

 

[Andromedus]

Yes - a 'state-local variable', that's exactly what I was after!  Thanks samme.