#HOWTO: BitFlag: Using the BitFlag class to keep state #

Introduction

This class is a copy of the BitFlag class on my site: http://divillysausages.com/blog/a_bitflag_class_for_as3

If you don't know what a bit flag is, check out http://en.wikipedia.org/wiki/Bit_field

Details

Check out the TestBitFlag.as file for the full details.

As with all examples, you need to init the framework before doing anything:

#!actionscript

DSAir.init( this ); // "this" is your Document class

BitFlags can be created with an optional class to check our flags against. This is useful if you want to make sure that your BitFlag can only have a specific set of flags. If you wish to do this, pass the class in the constructor:

#!actionscript

var flag:BitFlag = new BitFlag( MyFlags );

##Adding flags##

You can add single flags by:

#!actionscript

flag.addFlag( 1 << 1 );

or multiple:

#!actionscript

flag.addFlags( 1 << 2, 1 << 3, 1 << 4 );

##Removing flags##

#!actionscript

flag.removeFlag( 1 << 1 );

or multiple:

#!actionscript

flag.removeFlags( 1 << 2, 1 << 3, 1 << 4 );

##Toggling flags##

Toggling a flag will add it if it's not there, and remove it if it is:

#!actionscript

flag.toggleFlag( 1 << 1 );

or multiple:

#!actionscript

flag.toggleFlags( 1 << 2, 1 << 3, 1 << 4 );

##Checking for flags##

You can check if your BitFlag has a specific flag set by using:

#!actionscript

flag.hasFlag( 1 << 1 );

or multiple:

#!actionscript

flag.hasFlags( 1 << 1, 1 << 2 )

By default, hasFlags() checks for all the flags. If one of the flags passed isn't present, then the whole function returns false. If you want to check for the presence of any of the flags, call:

#!actionscript

flag.hasAnyFlag( 1 << 1, 1 << 2 )

##Using a custom flag class##

If you want to use a custom class so your BitFlag can only have specific flags added to it, you can pass the class into the constructor. The class is vetted for valid flags. For example, if we had a class like this:

#!actionscript

internal class MyFlags
{
    public static const ONE:int             = 1 << 1;
    public static const TWO:uint            = 1 << 2;
    public static const IGNORED_STRING:String   = "random";
    public static const IGNORED_INT:int         = 25;
    public static const IGNORED_NUMBER:Number   = 1.0;
    public static const TOO_LARGE:int       = 1 << 31;
}

then only ONE and TWO will be considered valid flags. IGNORED_STRING is ignored because it's a String, IGNORED_INT is ignored because it's not a flag, IGNORED_NUMBER is ignored because it's not an int or an uint, while TOO_LARGE is ignored as it's too big (you can only have 30 flags in a single BitFlag).

If you create a BitFlag with a flag class, then any of the calls to it's functions will first pass through a check function to see if they're alright.