Extend Source prototype to have a memory object

Question

I want to store some information about energy sources that I am harvesting. Ideally I would use mySource.memory.taken but Source does not have a memory property.

I could implement something like this:

Source.prototype.memory = function() {
    return Memory.sources[this.id];
}

But can I implement the same thing as a property like other game objects rather than a method? Or is there a better approach than this?

Answer 1

Yes, you can. You have to implement Getter/Setter interface using Object.defineProperty. Here is the complete solution based on the existing game code:

Object.defineProperty(Source.prototype, 'memory', {
    get: function() {
        if(_.isUndefined(Memory.sources)) {
            Memory.sources = {};
        }
        if(!_.isObject(Memory.sources)) {
            return undefined;
        }
        return Memory.sources[this.id] = Memory.sources[this.id] || {};
    },
    set: function(value) {
        if(_.isUndefined(Memory.sources)) {
            Memory.sources = {};
        }
        if(!_.isObject(Memory.sources)) {
            throw new Error('Could not set source memory');
        }
        Memory.sources[this.id] = value;
    }
});