Creating An EASE function reference

[notarysojac]

Maybe this will save somebody some time - and help to keep their code more manageable.

 

In an ever vigilant effort to avoid embedded magic numbers in my code, and, in

consideration of the fact that STRINGS are often just another form of magic number,

I created a function to return a reference that could be used with calls to the Greensock Tweens.

 

As my ActionScript is always data-driven from an XML file, I embed the easename and easekind

in the XML - then use that to create the function reference pass into the Greensock Tween.

The advantage here is that I can change behavior without the need to recompile my SWF app.

 

Of course, there's much more contained in the real XML file - the contents shown here are limited for clarity.

 

When I need to create an easement reference to a Tween - it might look something like shown below.

 

// XML textfile contents:
<?xml version="1.0" encoding="UTF-8"?>




Regular
easeInOut




Elastic
easeOut





// CONTAINED IN MY ACTIONSCRIPT SOURCE FILES
...
var tween_func:Function  = null; 
var easename:String      = "";
var easekind:String      = "";
...
try { easename = thexml.items.item[index].easedef.easename; } catch(easenameerr:Error) { ; }
try { easekind = thexml.items.item[index].easedef.easekind; } catch(easekinderr:Error) { ; }
...
if((null != easename) && (0 < easename.length) &&
  (null != easekind) && (0 < easekind.length))
 tween_func = fetchEasingFunction(easename, easekind);
...

// ----------------------------------------------------------------
// in a function someplace
....
TweenMax.fromTo(dispObj, tween_duration, 
  { x:fXpos, y:fYpos },
  { x:tXpos, y:tYpos, ease:tween_func });
...
// ------------------------------------------------------------
// these are in my [b]Contants.as[/b] file - then included into the class file 

private const  PKG:String                 = "MyClassName::";
private const  BACK_FUNCTION:String       = "Back";
private const  BOUNCE_FUNCTION:String     = "Bounce";
private const  ELASTIC_FUNCTION:String    = "Elastic";
private const  REGULAR_FUNCTION:String    = "Regular";
private const  STRONG_FUNCTION:String     = "Strong";
private const  NONE_FUNCTION:String       = "None";

private const  EASEIN_BEHAVIOR:String     = "easeIn";
private const  EASEOUT_BEHAVIOR:String    = "easeOut";
private const  EASEINOUT_BEHAVIOR:String  = "easeInOut";
private const  EASENONE_BEHAVIOR:String   = "easeNone";

// -------------------------------------------------------------

private function fetchEasingFunction(functionkind:String, functionname:String):Function
 {
 var result:Function = null; 

 trace(PKG+"fetchEasingFunction - functionkind["+functionkind+"] functionname["+functionname+"]");
 switch(functionkind)
   {
   case BACK_FUNCTION:
     switch(functionname)
       {
       case EASEIN_BEHAVIOR: result = Back.easeIn; break;
       case EASEOUT_BEHAVIOR: result = Back.easeOut; break;
       case EASEINOUT_BEHAVIOR: result = Back.easeInOut; break;
       default: break;
       }
   break;

   case BOUNCE_FUNCTION:
     switch(functionname)
       {
       case EASEIN_BEHAVIOR: result = Bounce.easeIn; break;
       case EASEOUT_BEHAVIOR: result = Bounce.easeOut; break;
       case EASEINOUT_BEHAVIOR: result = Bounce.easeInOut;  break;
       default: break;
       }
   break;

   case ELASTIC_FUNCTION:
     switch(functionname)
       {
       case EASEIN_BEHAVIOR: result = Elastic.easeIn; break;
       case EASEOUT_BEHAVIOR: result = Elastic.easeOut; break;
       case EASEINOUT_BEHAVIOR: result = Elastic.easeInOut; break;
       default: break;
       }
   break;

   case REGULAR_FUNCTION:
     switch(functionname)
       {
       case EASEIN_BEHAVIOR: result = Regular.easeIn; break;
       case EASEOUT_BEHAVIOR: result = Regular.easeOut; break;
       case EASEINOUT_BEHAVIOR: result = Regular.easeInOut; break;
       default: break;
       }
   break;

   case STRONG_FUNCTION:
     switch(functionname)
       {
       case EASEIN_BEHAVIOR: result = Strong.easeIn; break;
       case EASEOUT_BEHAVIOR: result = Strong.easeOut; break;
       case EASEINOUT_BEHAVIOR: result = Strong.easeInOut; break;
       default: break;
       }
   break;

   case NONE_FUNCTION:
     {
     switch(functionname)
       {
       case EASEIN_BEHAVIOR: result = None.easeIn; break;
       case EASEOUT_BEHAVIOR: result = None.easeOut; break;
       case EASEINOUT_BEHAVIOR: result = None.easeInOut; break;
       case EASENONE_BEHAVIOR: result = None.easeNone; break;
       }
     }
   default:
   break;
   }

 return(result);
 }
// -----------------------------------------------------------------

[GreenSock]

Have you checked out the EaseLookup class? It sounds like it does the same sort of thing (with a bit less code)

 

import com.greensock.easing.EaseLookup;

TweenLite.to(mc, 1, {x:100, ease:EaseLookup.find("Elastic.easeOut")});

 

There's documentation at http://www.greensock.com/as/docs/tween/ too.