Adobe Flash Professional CC 2014 v.13.0 - Manual (Page 873)

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the SWF file, the class definition remains in memory. To save memory, explicitly delete any custom classes in unloaded SWF files. Use the
delete statement and specify the fully qualified class name, such as: delete foo.bar.CustomClass.
Limit the use of global variables, because they are not marked for garbage collection if the movie clip that defined them is removed.
Avoid using the standard user interface components (available in the Components panel in Flash). These components are designed to run on
desktop computers and are not optimized to run on mobile devices.
Whenever possible, avoid deeply nested functions.
Avoid referencing nonexistent variables, objects, or functions. Compared to the desktop version of Flash Player, Flash Lite 2 looks up
references to nonexistent variables slowly, which can significantly affect performance.
Avoid defining functions using anonymous syntax. For example, myObj.eventName = function{ ...}. Explicitly defined functions are more
efficient, such as function myFunc { ...}; my Obj.eventName = myFunc;.
Minimize the use of Math functions and floating-point numbers. Calculating these values slows performance. If you must use the Math
routines, consider precalculating the values and storing them in an array of variables. Retrieving the values from a data table is much faster
than having Flash calculate them at run time.
For more tips and techniques for creating content for mobile phones and devices, see www.adobe.com/go/learn_cs_mobilewiki_en .
Managing Flash Lite file memory for mobile devices
Flash Lite regularly clears from memory any objects and variables that a file no longer references. This is known as garbage collection. Flash Lite
runs its garbage-collection process once every 60 seconds, or whenever usage of file memory increases suddenly by 20% or more.
Although you cannot control how and when Flash Lite performs garbage collection, you can still free unneeded memory deliberately. For timeline
or global variables, use the delete statement to free the memory that ActionScript objects use. For local variables—for example, a variable defined
within a function definition—you can’t use the delete statement to free an object’s memory, but you can set to null the variable that references the
object. This frees the memory that the object uses, provided there are no other references to that object.
The following two code examples show how to free memory that objects use by deleting the variable that references those objects. The examples
are identical, except that the first example creates a timeline variable and the second creates a global variable.
// First case: variable attached to a movie or
// movie clip timeline
//
// Create the Date object.
var mcDateObject = new Date();
// Returns the current date as a string.
trace(mcDateObject);
// Delete the object.
delete mcDateObject;
// Returns undefined.
trace(mcDateObject);
//
// Second case: global variable attached to a movie or
// movie clip timeline
//
// Create the Date object.
_global.gDateObject = new Date();
// Returns the current date as a string.
trace(_global.gDateObject);
// Delete the object.
delete _global.gDateObject;
// Returns undefined.
trace(_global.gDateObject);
As mentioned previously, you can’t use the delete statement to free memory that a local function variable uses. Instead, set the variable reference
to null, which has the same effect as using delete.
function func()
{
// Create the Date object.
var funcDateObject = new Date();
// Returns the current date as a string.
trace(funcDateObject);
// Delete has no effect.
delete funcDateObject;
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