How to automatically choose a model (MVC) based on the url?

Design-Dolphin

Dear Forum members,

I have searched for this and been trying to figure it out. However I am getting stuck.

So far I have a database in which there are categories.

These categories get automatically rewritten to form pretty url's.
Queries get selected based on the url.

The part I am getting stuck on is selecting models based on the url. What I am able to do so far is declare variables, and then have these match and choose models accordingly. However this turns out to be quite tedious, plus I want to do this automagically.

From what I can tell from php it should be possible, or am I trying do something that cannot yet be done?

It goes without saying that I want to do all this safely.

Thank you in advance for any advice and/ or pointers in the right direction.

NogDog

Sounds like you want to use a factory pattern, perhaps?

Design-Dolphin

Thank you for your response. 🙂

To tell you the truth unfortunately the information on that page is way over my head, so I would have to study that further to see if it would help. Also when I posted I confused the definition of models and views. My apologies.

I believe I may have found the solution after a big duh :rolleyes: moment. I forgot a step:

As I want to select models and views automatically based on what page I want to be displayed, I would need to find a way to do this. However, in doing so I forgot that the view should also be dynamic. Instead I was still naming the views to the actual category names. Allow me to illustrate:

I want three different setups:
1. A frontpage
2. A frontpage for main categories and a subpage for subcategories
3. Different view depending on the sort of articles.

The possible solution:

Add database columns in which the user can choose what type the article is, whether the article is to displayed on the main front page or a category front page.

Define the views based on the 'type of view' instead of based on for example the category name.

From that I can run a 'WHERE' in the MySQL query and declare variables. Based on which it chooses the correct view.

Or is the way you suggested better, and am I thinking in the wrong direction?

NogDog

My suggestion would be more specific to something where you had multiple classes with the same interface (e.g. they are child classes of the same abstract class), with the "factory" method allowing the program to decide at run-time which "child" class to instantiate. Whether or not such an approach would make sense to some or all of your situation may largely depend on the overall design, such as whether each model shares the same interface or not.

Your database idea seems workable to me, though I cannot say at this point whether or not I would take that approach myself as I don't know all the details.

You might find it useful to take a look at how some of the MVC frameworks out there do things. CodeIgniter has very good documentation, and Symfony is another popular one worth a look for comparison. A little Googling will locate quite a few others, too. (The only one I've worked with so far is CodeIgniter, so I'm really not qualified to make any comparisons at this point.)

Design-Dolphin

Thank you. CodeIgniter is impressive, I agree. I spent some time looking at a while ago. I have looked at some MVC frameworks to see how they do it. Unfortunately it gets very complicated quickly. Although I have to praise a couple of frameworks which write tutorials on the subject. At least giving some insight on where to start.

The database method actually proved to be a bit of a pain, and I also looked at different methods until I got the follow code to work. Mind you this is alfa code, and therefore in my opinion not suited for live websites as such, till debugged and tested fully. For now it does the job.

I came to the solution through the following: 'URL info' (http://nl2.php.net/manual/en/ref.url.php). When I read the 'parse_url' (http://nl2.php.net/manual/en/function.parse-url.php) It showed a link to
'pathinfo' (http://nl2.php.net/manual/en/function.pathinfo.php). Then the code uses mysql_fetch_assoc (http://nl2.php.net/mysql_fetch_assoc) to fetch a result row as an associative array.

The code does go out that the pretty url path is stored in the database as 'this-is-a-url' (without the quotes and with no extension). Although you could probably save it with extension as well. Like I said this code is alfa stage. With for example str_replace() you could technically do the pretty url rewriting on the fly. It is unknown to me what the server overhead exactly would be using str_replace() on the fly. Haven't tested that (yet) fully. From what I read about str_replace() so far it will add more overhead.

Choose model/view based on pretty url

<?php
$home ='http://domain_without_ext_and_slash';
$home_variable = $this_home . $_SERVER['REQUEST_URI'];
$path = $home_variable;
$file = dirname($path); 
$path_parts = pathinfo($home_variable);
$qinfo = $path_parts['filename'];

$sql = "SELECT field1, field2, field3 
        FROM   database
        ";

$result = mysql_query($sql);

if (!$result) {
    echo "Could not successfully run query ($sql) from DB: " . mysql_error();
    exit;
}

if (mysql_num_rows($result) == 0) {
    echo "No rows found, nothing to print so am exiting";
    exit;
}

while ($row = mysql_fetch_assoc($result)) {
    $field1 = $row["relevant_row1"];
    $field2 = $row["relevant_row2"];
    $field3 = $row["relevant_row3"];

if ( $home_variable == 'http://domain.ext/' ):
require ('file1.php');
elseif ($field1 == $qinfo):
require ('file2.php');
elseif ($field2 == $qinfo):
require ('file3.php');
elseif ($field3 == $qinfo):
require ('file4.php');
else:
echo 'not found';
endif;

} mysql_free_result($result);
?>

The mysql_free_result command does give an error at the this point, and I am not sure why at the moment. Clearing the mysql query gives us a clean slate for following queries. Depending on your personal need of course. One possible caveat: if this would have to be done for 10,000+ records it might add up and become slow. I am not sure. Although using caching that overhead could be resolved in certain setups. (the same goes for str_replace as well).

.htacces

<IfModule mod_rewrite.c>
Options +FollowSymLinks
IndexIgnore */*
RewriteEngine On
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteRule .* index.php [L] 
</IfModule>

Personally, I would like to add a check, if not included already, that checks to make sure the relevant php files are on the home server. I am not sure how safe the current code is. Nor am I sure if it is proper code writing.