Posts Tagged ‘Signals’

• By Rich

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  github, Signals, TypeScript

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  TypeScript Signals released – Think outside the Event

  3rd Apr 2013

  3

  Signals are a light-weight, strongly typed messaging tool and we use them extensively in our game framework. And we’ve just released our TypeScript implementation for others to benefit from. It’s a conversion of js-signals by Miller Medeiros, which is of course in turn a conversion of AS3-Signals by Robert Penner.

  You can get TypeScript-Signals from github.

  If you are unfamiliar with Signals, how they work and how they compare to Events then this short summary is well worth a quick read, but to summarise:

  • A Signal is essentially a mini-dispatcher specific to one event, with its own array of listeners.
  • A Signal gives an event a concrete membership in a class.
  • Listeners subscribe to real objects, not to string-based channels.
  • Event string constants are no longer needed.
  • Signals are inspired by C# events and signals/slots in Qt.

  I ported over all of the 18 unit tests to TypeScript as well. So you have plenty of examples: from adding a basic listener up to manual binding and dynamic context switching.

  Here is an example of how we use a Signal within our Position component in our framework. In this case ‘updated’ is our Signal and when the Position component is updated we dispatch it:

  this.updated.dispatch(this._point.x, this._point.y, this._z, this.cssTranslate3d, this.cssLeft, this.cssTop);

  Anything that is listening to the ‘updated’ Signal is notified of the new values being sent. For example our Sprite game object listens for updates:

  this.position.updated.add(this._updatePosition, this);

  And a local private method _updatePosition responds to the new values being sent.

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