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Enum toArray()

By klejnieks on March 29, 2008

There have been plenty of times that Ive needed to reuse the values of my enums as an array. A good example of this would be an enumeration of US states. There are many ways of doing this, however I find that writing an enumeration of static constants gives me the most flexibility and accuracy in my code.

In a recent project I had a user registration form which has a drop down component for the state you live in. Because another area of my application required that I was able to test against a users state I created an enum of the US state. Now in this form I was trying to avoid retyping all of these states into the fields data provider, besides it being tremendously tedious, it breaks the DRY principle.

I remembered from a different conversation I had with paul that there was a way to get actionscript to dump out the contents of a class into an xml list using describeType()

Using the describeType() method I was now able to get all of my constants in my class into a nice little array i could use as a data provider like this:

package com.lejnieks.poc.model.enums
{
	import flash.utils.describeType;
 
	public class USAStates
	{
		public static const ALABAMA:String = "Alabama";
		public static const ALASKA:String = "Alaska";
		public static const ARIZONA:String = "Arizona";
		public static const ARKANSAS:String = "Arkansas";
		public static const CALIFORNIA:String = "California";
		public static const COLORADO:String = "Colorado";
		public static const CONNECTICUT:String = "Connecticut";
		public static const DELAWARE:String = "Delaware";
		public static const DISTRICT_OF_COLUMBIA:String = "District Of Columbia";
		public static const FLORIDA:String = "Florida";
		public static const GEORGIA:String = "Georgia";
		public static const HAWAII:String = "Hawaii";
		public static const IDAHO:String = "Idaho";
		public static const ILLINOIS:String = "Illinois";
		public static const INDIANA:String = "Indiana";
		public static const IOWA:String = "Iowa";
		public static const KANSAS:String = "Kansas";
		public static const KENTUCKY:String = "Kentucky";
		public static const LOUISIANA:String = "Louisiana";
		public static const MAINE:String = "Maine";
		public static const MARYLAND:String = "Maryland";
		public static const MASSACHUSETTS:String = "Massachusetts";
		public static const MICHIGAN:String = "Michigan";
		public static const MINNESOTA:String = "Minnesota";
		public static const MISSISSIPPI:String = "Mississippi";
		public static const MISSOURI:String = "Missouri";
		public static const MONTANA:String = "Montana";
		public static const NEBRASKA:String = "Nebraska";
		public static const NEVADA:String = "Nevada";
		public static const NEW_HAMPSHIRE:String = "New Hampshire";
		public static const NEW_JERSEY:String = "New Jersey";
		public static const NEW_MEXICO:String = "New Mexico";
		public static const NEW_YORK:String = "New York";
		public static const NORTH_CAROLINA:String = "North Carolina";
		public static const NORTH_DAKOTA:String = "North Dakota";
		public static const OHIO:String = "Ohio";
		public static const OKLAHOMA:String = "Oklahoma";
		public static const OREGON:String = "Oregon";
		public static const PENNSYLVANIA:String = "Pennsylvania";
		public static const RHODE_ISLAND:String = "Rhode Island";
		public static const SOUTH_CAROLINA:String = "South Carolina";
		public static const SOUTH_DAKOTA:String = "South Dakota";
		public static const TENNESSEE:String = "Tennessee";
		public static const TEXAS:String = "Texas";
		public static const UTAH:String = "Utah";
		public static const VERMONT:String = "Vermont";
		public static const VIRGINIA:String = "Virginia";
		public static const WASHINGTON:String = "Washington";
		public static const WEST_VIRGINIA:String = "West Virginia";
		public static const WISCONSIN:String = "Wisconsin";
		public static const WYOMING:String = "Wyoming";
 
		public function USAStates() {}
 
		public static function toArray():Array
		{
			var states:Array = new Array();
			var classInfo:XML = describeType(USAStates);
			for each (var v:XML in classInfo..constant)
			{
				var name:String = String(v.@name);
			    	var value:String = USAStates[name];
			    	states.push(value);
			}
			states.sort();
			return states;
		}
 
	}
}

Now I can use my standard enum as an array or dataprovider like this:

<mx:ComboBox id="state" width="250" dataProvider="{USAStates.toArray()}" />

Posted in | Tagged , | 1 Response

One response to “Enum toArray()”

  1. Eric Feminella
    Eric Feminella January 24, 2009 at 7:34 pm |

    What’s up Ken. Interesting post and a much better solution than what you might typically see; an additional Array of values redundantly mirroring those of the constants, in which case should America happen to acquire another state (like Canada – just kidding) and the Array is not updated then everything would be out of sync. Good example of adhering to the DRY principle.

    One suggestion I would make would be to cache the Array so as to avoid the expensive overhead of invoking describeType(); for all subsequent calls.

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