ActionScript problem with prototype and static type variables

I'm developing a flash (Flash 9, AS3) to connect to a server and send/receive/parse data to a chat on JavaScript/HTML. I have a structure like this:

package {
    public class myClass {
     String.prototype.escapeHtml = function() {
      var str = this.replace(/&/g, "&");
      str = str.replace(/</g, "&lt;");
      str = str.replace(/>/g, "&gt;");
      return str;
     }

     function writeToBrowser(str:String) {
      ExternalInterface.call("textWrite",str.escapeHtml());
     }
    }
}

When I compile it, I get this error:

1061: Call to a possibly undefined method escapeHtml through a reference with static type String.

If I remove the :String, it all works fine, but then I'd have to check if str is a String and if it's not undefined and so on.

I have many functions like this on my code, many of them receive user-entered data, so I think that removing the :String and doing many checks on every function isn't the best approach.

How can I make this right?

From stackoverflow

• Prototype is actually legacy.

  You should extend the String class and use your custom class

  package {
      public class myClass {
  
          public function writeToBrowser(str:CustomString) {
                  ExternalInterface.call("textWrite",str.escapeHtml());
          }
      }
      public class CustomString {
  
          public function escapeHtml():String {
                  var str = this.replace(/&/g, "&");
                  str = str.replace(/</g, "&lt;");
                  str = str.replace(/>/g, "&gt;");
                  return str;
          }
      }
  }
  

  Mauricio : Thanks, that worked perfectly!

  Mauricio : Actually, there's a problem. I can't actually extend the String class ("1016: Base class is final."), so I loose methods like split, replace, etc. and I need them.

• Then just define the function:

  public function escapeHtml( str : String ) : String
  {
      var str = this.replace(/&/g, "&");
      str = str.replace(/</g, "&lt;");
      str = str.replace(/>/g, "&gt;");
  
      return str;
  }
  

  in your class.

  And call it:

  public function writeToBrowser( str : String )
  {
      ExternalInterface.call( "textWrite", escapeHtml( str ) );
  }
  

  :)

  Mauricio : That would solve the problem, but when you have function(function2(function3(str))) it's just ugly. Probably that's my bad coding.

• you get an error because the compiler is in strict mode. if you want to stay in strict mode you can try this:

  ExternalInterface.call("textWrite",str["escapeHtml"]() );
  

  Mauricio : That was actually it. I didn't remember I'd put it in strict mode.