Intereactive Web Design - Sugar Land, TX

One thing I love about writing javascript with the Mootools framework is that it really pushes me to write better code through it’s uses of classes and general OOP nature. This morning I ran into an issue of trying to dynamically call a certain method from our form validation class. I couldn’t figure out how to call a method that’s name was stored in a variable.

Let me explain a little further. The problem is that we need to tell the class that on form X we want to run validation method X that is very specific to that form (various ajax calls, etc…). So I needed a way to tell the class what method to run, basically calling a method dynamically from a variable. After searching the net and trial/error I finally figured it out. By using the syntax: “this[variable_name]()” you can call a method with the name stored in the variable. You can use this with any Object that uses JSON as well. Here’s a quick example.

Given the following HTML we can have a class run a specific function

<form id = "form_X" rel = "method_X">

And here is the test class that shows how to dynamically call the method.

var test = new Class({

    initialize: function() {
        // this value will always be "method_X" or "method_Y"
        action = $('form_X').get('rel');

        // here we use the variable "action"
        // to call a method on the fly
        this[action]();
    },

    method_X: function() {
        // do some form X validation
    },

    method_Y: function() {
        // do some form Y validation
    }
});