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HashCodeFactory

Kind of class:	public class
Package:	com.bourre.core
Inherits from:	none
Classpath:	com.bourre.core.HashCodeFactory
File last modified:	Monday, 24 November 2008, 11:36:49

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/*
 * Copyright the original author or authors.
 * 
 * Licensed under the MOZILLA PUBLIC LICENSE, Version 1.1 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.mozilla.org/MPL/MPL-1.1.html
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */    
package com.bourre.core
{
    import flash.utils.Dictionary;    

    /**
     * The <code>HashCodeFactory</code> class provides convenient methods
     * to emulate the behavior of the Java&trade; <code>Object.hashcode()</code>
     * method. The hashcode factory provides an unique identifier for any
     * instance in an application.
     * <p>
     * However, there is a major difference between the Java&trade; behavior
     * and the Flash&trade; behavior. In Java&trade; the hashcode method
     * will return the same value for two different instance of the same
     * class which have the same properties value, in Flash&trade; the 
     * hashcode factory will return a different identifier for all instances
     * even if their properties are equals.
     * </p>
     */
    public class HashCodeFactory
    {
        
        static private var _nKEY : Number = 0;
        
        /**
         * A hash map which store the generated keys for each object for which
         * an identifier was generated. Objects are stored as weak reference
         * so they will be collected as any other object which has no hashcode
         * identifier.
         */
        static protected const _oHashTable : Dictionary = new Dictionary( true );
        
        /**
         * Returns the hashcode key associated to the passed-in object.
         * If the objects has not yet a hashcode, the function will generate
         * one and then register the object with its hashcode.
         * 
         * @param    o    object for which get the hashcode key
         * @return    the string hashcode for the passed-in object
         */
        static public function getKey ( o : * ) : String
        {
            if( !hasKey ( o ) )
                _oHashTable[ o ] = getNextKey ();
            
            return _oHashTable[ o ] as String;
        }
        
        /**
         * Returns <code>true</code> if the passed-in object already
         * have a hashcode key.
         * 
         * @param    o    object for which verify the presence of a hashcode key    
         * @return    <code>true</code> if the passed-in object already
         *             have a hashcode key
         */
        static public function hasKey ( o : * ) : Boolean
        {
            return _oHashTable[ o ] != null;
        }
        
        /**
         * Returns the next unique identifier, two consecutives
         * call to the <code>getNextKey</code> will generate two
         * different keys. To get the next key without changing 
         * the next call result use the <code>previewNextKey</code>
         * method.
         * 
         * @return    the next unique identifier
         * @see        #previewNextKey()
         */
        static public function getNextKey () : String
        {
            return "KEY" + _nKEY++;
        }
        
        /**
         * Returns the next key the <code>getNextKey</code>
         * will return, without causing the <code>getNextKey</code>
         * method returning a different key. Calling several times
         * the <code>previewNextKey</code> method will never affect
         * the next call of the <code>getNextKey</code> method.
         * 
         * @return    a preview of the next unique identifier
         */
        static public function previewNextKey () : String
        {
            return "KEY" + _nKEY;
        }
    }
}

The HashCodeFactory class provides convenient methods
to emulate the behavior of the Java™ Object.hashcode()method. The hashcode factory provides an unique identifier for any
instance in an application.

However, there is a major difference between the Java™ behavior
and the Flash™ behavior. In Java™ the hashcode method
will return the same value for two different instance of the same
class which have the same properties value, in Flash™ the
hashcode factory will return a different identifier for all instances
even if their properties are equals.

Summary

Class methods

getKey (o:*) : String
- Returns the hashcode key associated to the passed-in object.
hasKey (o:*) : Boolean
- Returns true if the passed-in object already
getNextKey : String
- Returns the next unique identifier, two consecutives
previewNextKey : String
- Returns the next key the getNextKeywill return, without causing the getNextKeymethod returning a different key.

Class methods

getKey

public static function getKey (

o:*) : String

Returns the hashcode key associated to the passed-in object.
If the objects has not yet a hashcode, the function will generate
one and then register the object with its hashcode.

Parameters:

object for which get the hashcode key

Returns:

the string hashcode for the passed-in object

getNextKey

public static function getNextKey (

) : String

Returns the next unique identifier, two consecutives
call to the getNextKey will generate two
different keys. To get the next key without changing
the next call result use the previewNextKeymethod.

Returns:

the next unique identifier

hasKey

public static function hasKey (

o:*) : Boolean

Returns true if the passed-in object already
have a hashcode key.

Parameters:

object for which verify the presence of a hashcode key

Returns:

true if the passed-in object already
have a hashcode key

previewNextKey

public static function previewNextKey (

) : String

Returns the next key the getNextKeywill return, without causing the getNextKeymethod returning a different key. Calling several times
the previewNextKey method will never affect
the next call of the getNextKey method.

Returns:

a preview of the next unique identifier