Tag Archives: Computing

MVC in Practice: Designing Models

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Existing Examples

Sketch

There are lots of examples online teaching you what is MVC, why it is good and how to develop an application using this pattern. However most of them use a predefined structure with already constructed database and only the connection between a database table and a model is described. Actually what happens before all this. The client tells you something he’d like to have in his application.

Just imagine the following situation. You’ve a client who tells you that he wants a blog. The blog has to have posts and users, and every user must write posts and every post must have comments. Also he wants a set of categories where each post will be attached to one ore more categories. And finally a blogroll – one ore more links to another blogs.

This is pretty general and does not pretend to be a full featured example. However the strategy to make a primary structure of the future models is to pickup the nouns in this paragraph. It is really simple:

The blog has to have posts and users, and every user must write posts and every post must have comments. Also he wants a set of categories where each post will be attached to one or more categories. And finally a blogroll – one ore more links to another blogs.

So far you can see there are five prototypes of database tables: post, user, comment, category and link.

It’s important to note that not every noun is ready to be a database table. In some cases, when the client is really smart, he can give you a more detailed description. Than there are nouns describing the other nouns, of course, they are supposed to be columns to those tables.

Every post must have title and description …

This is what we can do for now. From a raw text you can design your database and models in the MVC architecture.

Friday Algorithms: JavaScript Bubble Sort

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Bubble Sort

Unsorted Array

This is one of the most slowest algorithms for sorting, but it’s extremely well known because of its easy to implement nature. However as I wrote past Fridays there are lots of sorting algorithms which are really fast, like the quicksort or mergesort. In the case of bubble sort the nature of the algorithm is described in its name. The smaller element goes to the top (beginning) of the array as a bubble goes to the top of the water.

There is a cool animation showing how bubble sort works in compare to the quick sort and you can practically see how slow is bubble sort because of all the comparing.

QuickSort vs. BubbleSort

Pseudo Code

Actually what I’d like to show you is how you can move from pseudo code to code in practice. Here’s the pseudo code from Wikipedia.

procedure bubbleSort( A : list of sortable items ) defined as:
  do
    swapped := false
    for each i in 0 to length(A) - 2 inclusive do:
      if A[i] > A[i+1] then
        swap( A[i], A[i+1] )
        swapped := true
      end if
    end for
  while swapped
end procedure

JavaScript Source

var a = [34, 203, 3, 746, 200, 984, 198, 764, 9];
 
function bubbleSort(a)
{
    var swapped;
    do {
        swapped = false;
        for (var i=0; i < a.length-1; i++) {
            if (a[i] > a[i+1]) {
                var temp = a[i];
                a[i] = a[i+1];
                a[i+1] = temp;
                swapped = true;
            }
        }
    } while (swapped);
}
 
bubbleSort(a);
console.log(a);

As a result you’ve a sorted array!

Sorted Array

Default Error Handling in Zend Framework

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Zend_Controller_Action_Exception

There’s a cool feature in Zend Framework when a controller or action doesn’t exists. That’s really useful, because you simply write an ErrorController.php in you default module and every action’s exception sends the user to this controller/action and the job is done for you. What is important here is to show the error message at least on the development stage. Actually the request stores it as a parameter. Here’s some source:

<?php
 
class ErrorController extends Zend_Controller_Action
{
    public function errorAction()
    {
        $errorHandler = $this->getRequest()->getParam('error_handler');
        /* @var $error Zend_Controller_Action_Exception */
        $error = $errorHandler->exception;
        echo $error->getMessage();
    }
}

Zend Framework: Simple Acl Front Controller Plugin

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access with Zend_Acl

Almost every web site need some abstraction over the access control list (ACL) to grant access of its users. As usual Zend Framework has quite good mechanism to deal with this – Zend_Acl.

Out in the web there are a lot of resources about Zend_Acl’s usage, so I ain’t going to cover it one more time, but simply copy/paste a very small front controller plugin implementing the basic usage of Zend_Acl.

Note that instead of defining the __construct() here is called preDispatch where the request is passed as a parameter. However only by copy pasting not every answer will be given. That’s why I’m going to write more about Zend_Acl in my future posts, for now only the source code:

<?php
 
class AclInit extends Zend_Controller_Plugin_Abstract
{
    public function preDispatch(Zend_Controller_Request_Abstract $request)
    {
        // create new acl object
        $acl = new Zend_Acl();
 
        // define resources. typically there are
        // only four resources from the CRUD functionality
        // but there can be added more resources
        $acl->add(new Zend_Acl_Resource('index'))
            ->add(new Zend_Acl_Resource('create'))
            ->add(new Zend_Acl_Resource('read'))
            ->add(new Zend_Acl_Resource('update'))
            ->add(new Zend_Acl_Resource('delete'));
 
        // define roles
        $acl->addRole(new Zend_Acl_Role('guest'))
            ->addRole(new Zend_Acl_Role('admin'));
 
        // define privileges
        $acl->allow('guest', array('index', 'read'))
            ->allow('admin');
 
        // setup acl in the registry for more
        Zend_Registry::set('acl', $acl);
 
        // check permissions
        if (!$acl->isAllowed('guest', $request->getActionName())) {
            $request->setControllerName('error');
            $request->setActionName('error');
        }
    }
}

document.forms[‘myform’].submit() is not a function?

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.submit()

You want to submit the form by clicking on a link or some other element on the page and this is a simple task. You know that by simply adding something like document.forms[‘the-form-name’].submit() this will work.

<form method="post" name="myform">
    <input type="text" name="user" />
    <a href="#" onclick="document.forms['myform'].submit();return false">Submit</a>
</form>

However you’d like to submit the form not only by clicking on that particular element, but also by clicking on the Enter while the focus is on a input field, and this wont work! That’s because you don’t have a input type=”submit”.

OK, first thing is to add a hidden input type=”submit” – than by clicking both on the Enter keyboard button and on the link with the onclick=”document.blah.blah.blah” will submit the form.

<form method="post" name="myform">
    <input type="text" name="user" />
    <input type="submit" name="submit" value="submit" style="display:hidden" />
    <a href="#" onclick="document.forms['myform'].submit();return false">Submit</a>
</form>

But this is not true!

Than you’ll receive the following message:

document.forms['myform'].submit() is not a function

Why? This isn’t working, but ever line seems to be OK. The answer is – don’t name the input type=”submit” with the trivial – “submit”. Just give it another name:

<form method="post" name="myform">
    <input type="text" name="user" />
    <input type="submit" name="something" value="something" style="display:hidden" />
    <a href="#" onclick="document.forms['myform'].submit();return false">Submit</a>
</form>