Off Topic...Sharing stuffs: July 2009

I was building mysql-5.1.36 in Ubuntu 9.04 - the Jaunty Jackalope. I was following the instructions given in INSTALL-SOURCE provided with the package. I was trying to create the MySQL data directory and initialize the grant tables by running this command:

$ sudo bin/mysql_install_db --user=mysql

I got this error:

FATAL ERROR: Could not find mysqld

The following directories were searched:

/usr/libexec
/usr/sbin
/usr/bin

If you compiled from source, you need to run 'make install' to copy the software into the correct location ready for operation.

If you are using a binary release, you must either be at the top of the level of the extracted archivem or pass the --basedir option pointing to that location.

After a bit googling and investigation, I found that this package mysql-common was already installed with Ubuntu 9.04 and there is a file my.cnf in /etc/mysql and db initialization was using this file instead of the one I copied to /etc with this command while following the INSTALL-SOURCE file:

$ sudo cp support-files/my-medium.cnf /etc/my.cnf

So the quick fix was to replace /etc/mysql/my.cnf with /etc/my.cnf that I copied earlier. I did these:

$ sudo mv /etc/mysql/my.cnf /etc/mysql/my_backup.cnf
$ sudo cp /etc/my.cnf /etc/mysql/

To use CodeIgniter's Pagination class to create pagination in one of our controller functions:



$this->load->library('pagination');

$config['base_url'] = 'http://example.com/index.php/test/page/';
$config['total_rows'] = '200';
$config['per_page']  = '20';

$this->pagination->initialize($config);

echo  $this->pagination->create_links();

The $config array contains your configuration variables. It is passed to the $this->pagination->initialize function. At a minimum we need the three configuration variables shown above.

base_url: Full URL to the controller class/function containing our pagination.
total_rows: Total rows in the result set we are creating pagination for.
per_page: Number of rows we intend to show per page

The pagination links provided by create_links function may not be appropriate for all cases. After-all clicking on these links will do page load which may not be desired on many situation. We may be interested to invoke a javascript function while clicking these links for doing AJAX style pagination. Still we want to use all other features provided by CodeIgniter's Pagination class. This can be accomplished simply. Just follow me ;)

1. All you need to do is adding some more functionality to the existing library i.e. CodeIgniter's Pagination class. To extend the native Pagination class you'll create a file named application/libraries/MY_Pagination.php, and declare your class with:



class MY_Pagination extends CI_Pagination
{
}

Here MY_ is the sub-class prefix, defined in application/config/config.php as follows:



$config['subclass_prefix'] = 'MY_';

If you need to use a constructor in yo ur class make sure you extend the parent constructor:



class MY_Pagination extends CI_Pagination
{
function MY_Pagination()
{
parent::CI_Pagination();
}
}

2. Next add some member variables to this class:



class MY_Pagination extends CI_Pagination
{
var $js_function_name   = '';
var $js_function_params         = array();

function MY_Pagination()
{
 parent::CI_Pagination();
}
}

js_function_name is the name of the javascript function to invoke when pagination links are clicked.

js_function_params is an array of parameters required for that javascript function. Our customized pagination will; add one more parameter for that javascript function; offset. While viewing the first page, offset=0. In the second page, offset = rows_per_page as defined by $config['per_page'] provided to the $this->pagination->initialize

 function.

js_href is the name of the div used in the pagination links as the value of the href attribute prefixed with #

3. Add a member function initialize_js_function to the class:



function initialize_js_function($jsFunction = array())
{
           if (count($jsFunction) > 0) {
               if (isset($jsFunction['name'])) {
                   $this->js_function_name = $jsFunction['name'];
               }
               if (isset($jsFunction['params'])) {
                   for ($i = 0; $i <>js_function_params[$i] = $jsFunction['params'][$i];
                   }
               }
           }
}

This function will be called from the controller function where we are using pagination stuffs.

4. Now modify the function create_links and add this modified function to the MY_Pagination class as create_js_links function. The modification basically ensures that each of the anchor tags generated, will have value of onclick attribute equals the javascript function as defined by the member variable js_function_name having the parameters as defined by the member variable js_function_params plus one extra parameter offset. A comma sperated list of the items in js_function_params will be created. Then the offset parameter will be appended in that comma separated list.



function create_js_links()
{
           // If our item count or per-page total is zero there is no need to continue.
           if ($this->total_rows == 0 OR $this->per_page == 0)
           {
               return '';
           }

           // Calculate the total number of pages
           $num_pages = ceil($this->total_rows / $this->per_page);

           // Is there only one page? Hm... nothing more to do here then.
           if ($num_pages == 1)
           {
               return '';
           }

           // Determine the current page number.
           $CI =& get_instance();

           if ($CI->config->item('enable_query_strings') === TRUE OR $this->page_query_string === TRUE)
           {
               if ($CI->input->get($this->query_string_segment) != 0)
               {
                   $this->cur_page = $CI->input->get($this->query_string_segment);

                   // Prep the current page - no funny business!
                   $this->cur_page = (int) $this->cur_page;
               }
           }
           else
           {
               if ($CI->uri->segment($this->uri_segment) != 0)
               {
                   $this->cur_page = $CI->uri->segment($this->uri_segment);

                   // Prep the current page - no funny business!
                   $this->cur_page = (int) $this->cur_page;
               }
           }

           $this->num_links = (int)$this->num_links;

           if ($this->num_links <>cur_page))
           {
               $this->cur_page = 0;
           }

           // Is the page number beyond the result range?
           // If so we show the last page
           if ($this->cur_page > $this->total_rows)
           {
               $this->cur_page = ($num_pages - 1) * $this->per_page;
           }

           $uri_page_number = $this->cur_page;
           $this->cur_page = floor(($this->cur_page/$this->per_page) + 1);

           // Calculate the start and end numbers. These determine
           // which number to start and end the digit links with
           $start = (($this->cur_page - $this->num_links) > 0) ? $this->cur_page - ($this->num_links - 1) : 1;
           $end   = (($this->cur_page + $this->num_links) < $num_pages) ? $this->cur_page + $this->num_links : $num_pages;

           // Is pagination being used over GET or POST?  If get, add a per_page query
           // string. If post, add a trailing slash to the base URL if needed
           if ($CI->config->item('enable_query_strings') === TRUE OR $this->page_query_string === TRUE)
           {
               $this->base_url = rtrim($this->base_url).'&'.$this->query_string_segment.'=';
           }
           else
           {
               $this->base_url = rtrim($this->base_url, '/') .'/';
           }

           //$js_output = $this->js_function_name . '(';
           $js_output = '';
           for ($paramIndex = 0; $paramIndex <>js_function_params); $paramIndex++) {
               $js_output = $js_output . $this->js_function_params[$paramIndex] . ',';
           }
           //$js_output = rtrim($js_output, ',');
           //$js_output .= ')';

           // And here we go...
           $output = '';

           // Render the "First" link
           if  ($this->cur_page > ($this->num_links + 1))
           {
               $js_output = rtrim($js_output, ',');
               $output .= $this->first_tag_open.'js_function_name.'('.$js_output.'0)'.'">'.$this->first_link.''.$this->first_tag_close;
           }

           // Render the "previous" link
           if  ($this->cur_page != 1)
           {
               $i = $uri_page_number - $this->per_page;
               //if ($i == 0) $i = '';
               $output .= $this->prev_tag_open.'js_function_name.'('.$js_output.$i.')'.'">'.$this->prev_link.''.$this->prev_tag_close;
           }

           // Write the digit links
           for ($loop = $start -1; $loop <= $end; $loop++)             {                 $i = ($loop * $this->per_page) - $this->per_page;

               if ($i >= 0)
               {
                   if ($this->cur_page == $loop)
                   {
                       $output .= $this->cur_tag_open.$loop.$this->cur_tag_close; // Current page
                   }
                   else
                   {
                       $n = ($i == 0) ? '' : $i;
                       $output .= $this->num_tag_open.'js_function_name.'('.$js_output.$n.')'.'">'.$loop.''.$this->num_tag_close;
                   }
               }
           }

           // Render the "next" link
           if ($this->cur_page < $num_pages)             {                 $output .= $this->next_tag_open.'js_function_name.'('.$js_output.($this->cur_page * $this->per_page).')'.'">'.$this->next_link.''.$this->next_tag_close;
           }

           // Render the "Last" link
           if (($this->cur_page + $this->num_links) < $num_pages)             {                 $i = (($num_pages * $this->per_page) - $this->per_page);
               $output .= $this->last_tag_open.'js_function_name.'('.$js_output.$i.')'.'">'.$this->last_link.''.$this->last_tag_close;
           }

           // Kill double slashes.  Note: Sometimes we can end up with a double slash
           // in the penultimate link so we'll kill all double slashes.
           //$output = preg_replace("#([^:])//+#", "\\1/", $output);

           // Add the wrapper HTML if exists
           $output = $this->full_tag_open.$output.$this->full_tag_close;

           return $output;
}

5. Now in the controller, where you are using pagination stuffs, initialize the pagition in this way:



//In actual scenario, populate it with number rows to paginate
$config['total_rows'] = 100;
$config['per_page'] = 10;
$config['first_link'] = 'First';
$config['last_link'] = 'Last';
//change it as per your controller's function's number of parameters
$config['uri_segment'] = 3;
$this->pagination->initialize($config);

$jsFunction['name'] = 'your_javascript_function_name';
//provide your params for the javascript function if there is any
//In my case, it is empty
$jsFunction['params'] = array();
$this->pagination->initialize_js_function($jsFunction);
//pass/use this $page_link in your view as per your need
$page_link = $this->pagination->create_js_links($pageNo);

This is the basic outline or structure. You have to write down your own javascript function to make ajax call and fill in the missing or leftover details ;)

Now taste the AJAXified pagiantion in action :D We have done a great job already ;)

You can download a complete sample or demo from here: http://www.mediafire.com/file/4ygym0trmjh/ajax_pagination_demo.zip

Off Topic...Sharing stuffs

Friday, July 24, 2009

Installing the Connector/J in Windows XP with JDK 1.6.0_14

Monday, July 20, 2009

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Friday, July 17, 2009

mysql-5.1.36 in Ubuntu 9.04: FATAL ERROR: Could not find mysqld

CodeIgniter: AJAX Pagination

mysql-5.1.36 in Ubuntu 9.04: No curses/termcap library found