Hype Symbol Cache

This is a quick release of a nerdy extension to solve the inconsistent Symbol-API provided by the runtime. Background being that the runtime applies initial values including a fresh copy of the Symbol API multiple times including when HypeSceneLoad, HypePrepareSceneForDisplay and HypeDocumentLoad runs. Meaning the runtime makes it hard on using the Symbol API consistently to store Symbol specific values like possible with hypeDocument. The symbol API stays constant in a scene but you have to redefine any additions on each “On Scene Load” or HypeSceneLoad. You can’t store a symbol specific counter or anything across scenes in the Symbol API.

This extension caches the Symbol API and always returns the first cached version. This way you can rely on it being stable and cached. Hence, the name. It also gives you a new callback “HypeSymbolInit” fired when a symbol is cached (so only fired once).

This is still in Beta. Feedback welcome.

Source:
HypeStableSymbol.js
HypeStableSymbol.min.js

Read about it here:

2 Likes

This is how you can use the new event. But that is optional the extension also works with the regular and built in events and symbol API calls.

function symbolInitTest (hypeDocument, element, event){
		console.log('HypeSymbolInit');
		var symbolInstance = hypeDocument.getSymbolInstanceForElement(element);
		// do your stuff…
	}
	
	window.HYPE_eventListeners.push({"type":"HypeSymbolInit", "callback":symbolInitTest});
2 Likes

could you eleborate on usecases? I’m confused … :slight_smile:

Simply put, you can store values and extensions in symbols. Basically, it allows adding methods to symbols while also keeping a “State” in individual symbols. Each symbol instance is an object much like hypeDocument and can also be “extended” tweaked and used for storage. In Hype you can already “out of the box” do this but the runtime resets any state (or extension) as every scene and document event “destroys” the symbol instance by fetching a new object describing it. If you only use On Scene Load to setup and the single scene context is enough for you, you can already do some stuff as is. But, you will hit a wall when trying to add methods in Document Load as they are reseted when switching to the subsequent scene (or moving from scene to scene). The same goes for state data of symbol instances you might want to retain across scenes.

I admit it’s a special case extension but there are use cases … specially when thinking about state driven component-based approaches using symbols.

This extension makes every symbol instance object “stable” or persistent… but I refrained from calling it persistent symbol instance to avoid confusion with persistent symbols as we are only talking about the symbol instance (object) being stable.
If you need a scene change to destroy/reset symbol instance objects (like it’s the default in regular Hype) you can call the method hypeDocument.purgeSymbolCache(). You can also purge the symbol cache for individual symbol instances using the element ID of the symbol with hypeDocument.purgeSymbolCacheForId(YOUR-ID);. Once a symbol is purged it will re-init on the next symbol load or when you fetch it again with the API. Speaking of it I might add a switch (Boolean) on the purge functions to re-init immediately.

thx :slight_smile:

so far i’ve never extended the SymbolInstanceObject … so never discovered the reset Hype does. Nice new feature :slight_smile:

What would you name this extension?

  • Stable Symbol
  • Persistent Instances

0 voters

The word instance suggests some js-object. where as symbol is also important, cause the subject is around symbols. what about: Stable Symbols Instances? :slight_smile:

1 Like

I presantly storing states in a global. i.e
each instance of a symbol has it’s own state saved, when the scene changes these are read back in.
I also have used this to direct a function run to which instance uses it.

Is this what you are meaning to help with… ?

1 Like

↑ look at project
1.1 Bugfixes, additional API and immediate refresh

Here is a simple example to illustrate the usage. This file has the extension included from the JsDelivr CDN (head over to the GitHub-Repository for further instructions and a minified version)

This is only one use case and the way I am using the init and load with Object.assign has nothing to-do with the extension. This could be extended and used in many ways. It’s just one example and way of doing it given a symbol instance is extended (counter). This is just to make the point and by no means a template or so…

function symbolInit (hypeDocument, element, event){
	console.log('HypeSymbolInit');
	var symbolInstance = hypeDocument.getSymbolInstanceForElement(element);
	var symbolElement = symbolInstance.element();
	switch (symbolInstance.symbolName()){
		case 'counter':
			Object.assign( symbolInstance, {

				_counter: 0,
				
				increase: function(){
					this._counter++;
					this.refresh();
				},
				
				decrease: function(){
					this._counter--;
					this.refresh();
				},
			
				getValue: function(){
					return this._counter;
				},

				refresh: function(){
					symbolElement.querySelector('.display').innerHTML = this._counter;
				},
				
			});
				
			symbolElement.querySelector('.upBtn').onclick = function(){
				symbolInstance.increase();
			}
			
			symbolElement.querySelector('.downBtn').onclick = function(){
				symbolInstance.decrease();
			}
			
			symbolInstance.refresh();
			break;
	}
}

function symbolLoad (hypeDocument, element, event){
	var symbolInstance = hypeDocument.getSymbolInstanceForElement(element);
	switch (symbolInstance.symbolName()){
		case 'counter':
			symbolInstance.refresh();
			break;
	}
}


window.HYPE_eventListeners.push({"type":"HypeSymbolInit", "callback":symbolInit});
window.HYPE_eventListeners.push({"type":"HypeSymbolLoad", "callback":symbolLoad});

Download:
HypeSymbolCache.hype.zip (57,5 KB)

Preview:
HypeSymbolCache.html

3 Likes