FLASH CS3
User Guide
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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.
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 Action-
Script 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
.
