Category Archives: Programming

Functional Programming, Programming 1 Comment

Data Abstraction Definition

Do yourself a favour, read the Structure and Interpretation of Computer Programs. It will teach you that:

The general technique of isolating the parts of a program that deal with how data objects are represented from the parts of a program that deal with how data objects are used is a powerful design methodology called data abstraction.

In my opinion OOP doesn’t favour data abstraction.
A class glues together data (attributes) and functions dealing with the data (methods). In functional programming languages, data and functions which operate on the data are kept separated promoting data abstraction.
I read this definition while learning Scheme with the beautiful Structure and Interpretation of Computer Programs (which I recommend for you health and safety).
Here, the explanation of functions and procedures (data manipulation) is kept separated from the explanation of how the data is represented, separation which should also be advocated in your source code.
Any comment is more than welcome.. it will help me to understand more and more!

JavaScript , 1 Comment

Javascript: Set nested object property.

Suppose you have a Javascript object with the following structure:

var obj = {firstname : "Nico",
           lastname:   "Balestra",
           hobbies: [{
                       name: "Clojure",
                       since: "01/03/2012"
                     },
                     {name : "Javascript",
                      since : "01/01/2011"}]
          };

and now suppose that your application is such that you need to set one of the attributes of the above object by pointing to that attribute through a Javascript path.
Because you work for a company using Serverside Javascript and you are not allowed to use any library of the like of jQuery, you need to find a way to achieve this yourself.
Therefore, suppose you need to set the date of my Javascript hobby so that it starts the 01/01/2010.
The path referring to that attribute would be obj.hobbies[1].since. So you would like to do something like:

setAttribute(obj, "hobbies[1].since", "01/01/2010");

And this is the setAttribute function

var setAttribute = function(object, path, value){
  var paths = path.split(".");

  var traverse = function(context, pathStack){
    var currPath = pathStack.shift();
    var arr = currPath.match(/\[\d*\]/);

    if (arr != null){
     var arrIdx = parseInt(arr[0].match(/\d+/)[0]);
     var newCurrPath = currPath.replace(/\[\d*\]/, "");
     
     traverse(context[newCurrPath][arrIdx], pathStack);

     }else if ((typeof context[currPath]) == "object"){
	traverse(context[currPath], pathStack);
     }else{
	context[currPath] = value;
    }
  };
	
  traverse(object, paths);
       	
}

I hope this may be of any help.
Nico