Data Management Made Easy Using Nennius: Advanced Data Handling - Creating the User Comments Component
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Now that we have finished configuring the application, let's create our basic Comments component. Just like last time, we'll start by creating the entry-point file. Name that file 'comments.php' and place it within the '/nennius/webapps/news/' directory. Then copy the following content into it:
<?php
# define location of component & descriptor files
$component_file = 'components/comments.php';
$descriptor_file = 'descriptors/comments.php';
# include parent nennius_component class
include_once "../../nennius.component.php";
include_once $component_file;
# create a new object to kick things off
new comments( $descriptor_file );
?>
Next let's move on to the Comments descriptor file ('/descriptor/comments.php'):
<?php
# set display name for component
$GLOBALS['g_main_display_name'] = 'User Comments';
# set primary db table name
$GLOBALS['g_db_primary_table'] = 'comments';
# set primary key for main db table
$GLOBALS['g_db_primary_table_key'] = 'id';
# set (optional) primary display field for db table
$GLOBALS['g_db_primary_table_name'] = 'subject';
# set required min. threshold for overall access
$GLOBALS['g_threshold_overall'] = $GLOBALS['USER'];
?>
So far things should look pretty familiar, which is good. At their most basic level, all Nennius components will look very similar. The components file ('/components/comments.php') is no exception. Let's create it next:
<?php
# basic comments component
class comments extends nennius_component {
# store class-wide reference to control object
# NOTE: this object is created by the nennius_component class
var $nennius_control = NULL;
#-----------------------------------------------------------------
# sets up necessary internal vars, creates new control object
# and passes self-reference to it
#-----------------------------------------------------------------
function comments( $p_component_descriptor_file ) {
# call out to constructor of parent class with descriptor file
$this->nennius_component( $p_component_descriptor_file );
} # END comments
#-----------------------------------------------------------------
# retrieves and returns assoc. array containing db column info
#-----------------------------------------------------------------
function get_info_db_array() {
$f_db_info_array = NULL;
# define primary key attribute for comments table
$f_db_info_array['id'] = (
array (
'db_field_name' => 'id',
'db_field_type' => 'int',
'db_field_length' => 3,
'db_primary_key' => TRUE,
# field is hidden from visibility at all times
'hidden_all' => TRUE
)
);
# news id - links comment entries to parent news release entry
$f_db_info_array['news_id'] = (
array (
'db_field_name' => 'news_id',
'db_field_display' => 'News Release',
'db_field_type' => 'int',
'db_field_length' => 36,
'db_field_required' => TRUE,
# foreign key DB information
'db_foreign_key' => 'id',
'db_foreign_display' => 'title',
'db_foreign_table' => 'news'
)
);
# date & time when comment was posted
$f_db_info_array['datetime'] = (
array (
'db_field_name' => 'datetime',
'db_field_display' => 'Date / Time',
'db_field_type' => 'datetime',
'db_field_length' => 19,
'db_field_required' => TRUE,
# set default value to be current date & time
'update_default' => date( 'Y-m-d H:i:s' ),
# set attribute to be searchable by min & max date range
'search_date_range' => TRUE
)
);
# commentor's name
$f_db_info_array['name'] = (
array (
'db_field_name' => 'name',
'db_field_display' => 'Name',
'db_field_type' => 'char',
'db_field_length' => 50,
# set field to be searchable using a partial-match criteria
'input_search_type' => 'TEXT',
'search_partial' => TRUE,
)
);
# comment's subject
$f_db_info_array['subject'] = (
array (
'db_field_name' => 'subject',
'db_field_display' => 'Subject',
'db_field_type' => 'char',
'db_field_length' => 100,
# set field to be searchable using a partial-match criteria
'input_search_type' => 'TEXT',
'search_partial' => TRUE,
)
);
# comment body / text
$f_db_info_array['comment'] = (
array (
'db_field_name' => 'comment',
'db_field_display' => 'Comment',
'db_field_type' => 'char',
# define size of textarea input
'input_update_type' => 'TEXTAREA',
'input_update_rows' => 10,
# hide field from search & view modes
'hidden_search' => TRUE,
'hidden_view' => TRUE
)
);
# after all attributes have been setup, return array
return $f_db_info_array;
} # END get_info_db_array()
#-----------------------------------------------------------------
# retrieves and returns assoc. array containing display headers
#-----------------------------------------------------------------
function get_info_header_array() {
$f_header_info_array = NULL;
# append default header messages
$f_header_info_array['news_id'] = 'News Information';
$f_header_info_array['name'] = 'User Information';
$f_header_info_array['subject'] = 'Comment';
# return header array
return $f_header_info_array;
} # END get_info_header_array()
} # END comments class
?>
Things should still look somewhat familiar. As you can see we've simply described the SQL table that stores our User Comments information, and set some basic configuration options about each of the component's attributes (aka SQL columns). However, a very important attribute was introduced with the 'news_id' column: the foreign key.
As previously stated, most data management systems will not only need to manage various data components but also control those components in relation to one another. Nennius allows for several methods of interaction between components, one of which is the foreign key attribute we have just identified. By specifying a foreign table, key, and display column we are providing Nennius with all of the information it needs to transparently link the Comments component to the News component. The result of this (in this example) is a drop-down menu containing all News entries, listed by title, that a user may pick from when creating or modifying a Comment record. This creates an association between Comments and News records.
We also introduced a new function in this component file: 'get_info_header_array()'. This function defines headers that are displayed above certain attributes when a record is being created or modified. This is a very useful tool when creating components with a high number of attributes. By using the 'get_info_header_array()' function a developer is easily able to categorize and organize the various form elements - making the resulting update form more user-friendly.
Next: Creating Component Dependencies >>
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