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Flash Reference Guide

Aug 22, 2003

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A fundamental object you need to get used to working with is the string object. The strength of the string object is that its only mission in life is to control how you work with strings of text.

So, what is a string? A string is typically a length of alphanumeric characters. The following example is a string:

"The quick brown fox jumps over the lazy dog"

I know, you are saying this just a sentence and you are correct. A string is just a collection of letters and numbers. The following is another example of a string:

"There 12 Caesars that ruled Rome"

This string contains a number, but the important thing to remember is that the string object treats numbers just like any other text character; it is not a number if it is in a string. For instance, you can not do mathematical calculations on a number in a string. The following example demonstrates two strings used in a mathematical equation:

"12" + "12" = 1212

The answer is not 24, as you might expect mathematically, but rather it consists of the two sets of characters put together. An example of two sets of words added together would look like this:

"Apple" + " " + "iPod"= "Apple iPod"

You will notice that a space is added in the middle. If this was not added, the two words would be run together like this: AppleiPod.

In ActionScript, string objects look and perform similarly to the examples provided above. The first step you need to take when working with strings is to first declare the string as an object, then name the string, provide a value type and then the value. The following example demonstrates this:

//Define string object, value type and value in parenthesis
var myTeststring1:string=string ("Howdy");

Additional strings can be created, such as the following:

var myTeststring2:string=string ("Partner");

The final step is to link both strings and run a test in Flash to see what the outcome looks like. Here I have a "trace" command binding the two strings together with an inline string, the "!" at the end of the equation:

trace (myTeststring1 + ", " + myTeststring2 + "!")

Extracting Values from a string

Values can be extracted from strings. In the following example you are going to extract specific values from a string object.

The following example creates a function that parses a string and looks for numbers in the string. Once the numbers are found, their values are posted to the Trace Output window.

//Sample string - you can substitute with your own
var inputStr:string = "something like 1agssag24dlfq230kf7";
// extracts all numerals form string and returns them as a Number object
function extractNumber (str:string){
  var char:string;
  var num:string = "";
  for(var i:Number = 0; i<str.length; i++){
    char = str.substr(i, 1);
    if(!isNaN(char)){
      num+=char
    }
  }
  return Number(num);
}
var num:Number = extractNumber(inputStr);
trace(num);
//Trace will look like 1242307

In a similar way, the following example parses strings held in an array to find matches. The values are posted to the Trace Output window:

//Names Array
names = [’Andy’, ’Andy2’, ’Bobby’, ’Catey’, ’Doogey’];
//Function to extract a match
function matchName (partial) {
  for (var k = 0; k<names.length; k++) {
    if (names[k] == partial) {
      continue;
    } else if (names[k].toLowerCase() == partial.toLowerCase()) {
      return names[k];
    }
    if ((names[k].substr(0, partial.length)).toLowerCase() == partial.toLowerCase()) {
      trace ("found possible match!");
      return names[k];
    }
  }
  return null;
}
//Tests
trace (matchName(’And’));
trace (matchName(’and’));
trace (matchName(’andy’));
trace (matchName(’Andy’));
trace (matchName(’Anc’));

Replacing Values

You can also take a string and replace values in the string with other values. The following example provides a class that looks for and replaces values in a string using the Split and Join method.

string.prototype.searchReplace=function(find,replace) {
  return this.split( find ).join( replace);
}

var mystring = "AAAAaaaaaaaaaaaaaaaaaaaa...";
trace(mystring);// Jaaaaaaaaaaaaazzzz...
var newstring = mystring.searchReplace("a","e");
trace( newstring ); // AAAAeeeeeeeeeeeeeeeee...

Working Examples

You may begin to think that strings are only useful for changing values. You would be wrong. A string can be used in a lot of scripts to add value. The following is an example of using a string to animate the letters "LOADING" on the screen while the main movie downloads. To view this script you will need to add a very large file, such as a bitmap image, and change your preview setting to simulate "Dial Up – 28.8kBps."

var s = 0;
var text = "LOADING";
function loadingAni() {
 text = text.substring(0, k)+text.charAt(k)+part2.toLowerCase()+text.substring(k+1, text.length);
 animOutput = text;
 text = text.toUpperCase();
 s++;
 if (s>(text.length-1)) {
  s = 0;
 }
}

You can also strings to modify values of other objects you are using in your movies. For instance, the following script will dynamically create values for movie clips. This is important for games and applications where you are building dynamic environments:

//random letters
function rCons(myLetter):string {
 var cArray:Array = new Array("b", "c", "d", "f", "g", "h", "j", "k", "l", "m", "n", "p", "qu", "r", "s", "t", "v", "w", "x", "y", "z", "z");
 var aNum:Number = new Number(Math.ceil(random(22)));
 myLetter = cArray[aNum];
 return (myLetter);
}
function rVowels(myLetter):string {
 var vArray:Array = new Array("a", "e", "i", "o", "u", "u");
 var bNum:Number = new Number(Math.ceil(random(6)));
 myLetter = vArray[bNum];
 return (myLetter);
}
function genName(myExt, mystring):string {
 var nNum2:Number = new Number(Math.floor(random(4)+3));
 var nText:string = new string("");
 for (i=0; i<nNum2; i++) {
  var tempNum1:string = rCons();
  var tempNum2:string = rVowels();
  nText += tempNum1;
  nText += tempNum2;
 }
 mystring = nText;
 mystring += myExt;
 return (mystring);
}
// example 1 
var nTt:string = genName("_mc");
// example 2 
var nT2:string = genName("");
trace(nTt);
trace(nT2);

The final example demonstrates how you can use a string to protect your movies. In this example a string, setURL, tells Flash what site the Flash movie can be played in. If the movie is copied and loaded into a new site then this script will prevent it from running.

setURL = "http://www.informit.com";
checkURL = getProperty("", _url);
validURL = true;
charIndex = 0;
while (charIndex<setURL.length) {
 tempChar1 = checkURL.charAt(charIndex);
 tempChar2 = setURL.charAt(charIndex);
 if (tempChar1 != tempChar2) {
  validURL = false;
  break;
 }
 charIndex++;
}
if (validURL) {
 gotoAndPlay(_currentframe+1);
} else {
 gotoAndPlay(_currentframe-1);
}

Summary

Strings are a fundamental to any ActionScript you write. The trick is to know how powerful they can be to your movies. In the above examples you should have acquired a taste of what you can do with the string object.

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