Ron Savage > DBIx-HTML-ClientDB-1.08 > DBIx::HTML::ClientDB

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Module Version: 1.08   Source  

NAME ^

DBIx::HTML::ClientDB - Convert sql into a client-side db with keyed access.

Synopsis ^

        use DBIx::HTML::ClientDB;

        my($object) = DBIx::HTML::ClientDB -> new
        (
                dbh          => $dbh,
                row_headings => 'Unit code,Unit code,Campus name,Unit name',
                sql          => 'select unit_code, unit_code, campus_name, unit_name ' .
                                'from unit, campus where unit_campus_id = campus_id ' .
                                'order by unit_code',
        );

        print $object -> javascript_for_client_db();
        print $object -> table();
        print $object -> javascript_for_client_init();

Description ^

This module takes a db handle, an SQL statement and a specially-formatted row_headings parameter, and builds an array of rows as returned by the SQL.

Then you ask for that array in HTML, ie as a table.

After a call to the table() method, you can call the size() method if you need to check how many rows were returned by the SQL you used.

Neither the module CGI.pm, nor any of that kidney, are used by this module. We simply output pure HTML.

However, for simplicity, this document pretends you are using CGI.pm rather than an alternative. The sentences would become too convoluted otherwise.

The output table is formatted as N rows of 2 columns:

First column

The first column contains the row headings you supply in the 'row_headings' parameter. 'row_headings' is a comma-separated list of strings you want to appear in the first column of the table.

There must be one string in 'row_headings' for each column mentioned in the SQL.

Second column

The second column contains the 'current record' in the database.

Now for the rows:

First row

The first row contains the first prompt string in the first column.

The first row contains a HTML popup menu in the second column.

This menu is what you use to choose the 'current record' in the database.

Since two (2) SQL columns are used to build this menu, two (2) strings from the row_headings parameter are consumed building the first row. The first of these 2 strings appears in the first column, as explained above. The second of these 2 strings is, much to your amazement, discarded!

This way of doing things makes it easy for you to count row_heading strings and their corresponding SQL columns, and makes it easy for me to cross-check your ability to count to 2 :-).

Other rows

Each other row contains a field in the 'current record'. The value in the first column comes from the row_headings parameter, and the value in the second column comes from the database.

The sum result is menu-driven access to the data returned by the SQL. All this is downloaded from your CGI script to the web client. Since changing the current menu item updates the other fields in this table using JavaScript, no message is sent to the web server, and hence you have maximum speed of access.

The whole point of the exercise is to give you simple code for simple access to simple data.

See examples/test-clientdb.cgi for an example which will make all this clear.

Distributions ^

This module is available both as a Unix-style distro (*.tgz) and an ActiveState-style distro (*.ppd). The latter is shipped in a *.zip file.

See http://savage.net.au/Perl-modules/html/installing-a-module.html for help on unpacking and installing each type of distro.

Usage ^

You create an object of the class by calling the constructor, 'new'.

Now call various methods to get the HTML and JavaScript.

Lastly, display the HTML as part of a form. You don't need a submit button because there is no need to transmit your menu selection to the CGI script. It's all about convenient access to a small database. Of course, you can easily use this as the basis of a more complex record-selection system.

Instead of the method javascript_for_client_init(), you can call the method javascript_for_client_on_load() to initialize a JavaScript onLoad event handler.

Note: The HTML menu name and all JavaScript function and global variable names have been deliberately chosen so as to not clash with other modules of mine in the DBIx::HTML::* namespace. Hence these modules can, in theory, all be used to build a single web page, and indeed, can (I hope) all be used to build a single form. No, I didn't actually test it.

Options ^

Here, in alphabetical order, are the options accepted by the constructor, together with their default values.

border => 0

This specifies whether or not the HTML table returned by the table() method has the border option set.

Valid values are 0 and 1.

This option is not mandatory.

dbh => ''

Pass in an open database handle.

This option is mandatory.

default => ''

Pass in the string (from SQL column 2) which is to be the default item on the popup menu. You supply here the visible menu item, not the value associated with that menu item.

If default is not given a value, the first menu item becomes the default.

See the discussion of the sql option for details about the menu items.

This option is not mandatory.

form_name => 'dbix_client_form'

The value of this parameter becomes the name of the form used in the JavaScript, and must be the name used by you in your call to CGI's start_form() or start_multipart_form() method.

This option is not mandatory, since it has a default value.

max_width => 0

When the database field values displayed in the second column of the table are input fields, this value becomes the 'size' parameter of those input fields.

A value of 0 means the data will be scanned and a value chosen which ensures no data is truncated in order to display the database field values.

This option is not mandatory.

menu_name => 'dbix_client_menu'

The value of this parameter is what you would pass into a CGI object when you call its param() method to retrieve the user's selection.

Hence you would do something like:

        my($name)   = 'fancy_menu';
        my($object) = DBIx::HTML::ClientDB -> new(menu_name => $name, ...);
        my($q)      = CGI -> new();
        my($id)     = $q -> param($name) || '';

This option is not mandatory, since it has a default value.

row_headings => 'a,b,...'

Pass in a comma-separated list of strings to use in the first column of the table.

There must be one string in 'row_headings' for each column mentioned in the SQL.

Since two (2) SQL columns are used to build the menu, two (2) strings from the row_headings parameter are consumed building the first row. The first of these 2 strings appears in the first column, as explained above. The second of these 2 strings is, much to your amazement, discarded!

This way of doing things makes it easy for you to count row_heading strings and their corresponding SQL columns, and makes it easy for me to cross-check your ability to count to 2 :-).

This option is mandatory.

sql => ''

Pass in the SQL used to select the data.

The SQL must select at least 2 columns. The first will be used as the value returned by a CGI object, for example, when you call its param() method. The second value will be used as the visible selection offered to the user on the menu.

Of course, the 2 columns selected could be the same:

        $obj -> set(sql => 'select campus_name, campus_name from campus ' .
                                        'order by campus_name');

But normally you would do this:

        $obj -> set(sql => 'select campus_id, campus_name from campus ' .
                                        'order by campus_name');

This means that the second column is used to construct visible menu items, and when an item is selected by the user, the first column is what is returned to your CGI script.

The question remains: After you do something like this:

        my($q)     = CGI -> new();
        my($id)    = $q -> param('dbxi_client_menu') || '';

how do you convert the value, eg campus_id, back into the database fields associated with the visible menu item, eg campus_name.

Simple: You call the param() method of the DBIx::HTML::ClientDB class:

        my(@field) = $object -> param($id);

The param() method returns () if the value of $id is unknown.

This option is mandatory.

Methods ^

javascript_for_client_db()

Returns JavaScript, including the <script>...</script> tags, which holds your data in a JavaScript db, and includes some JavaScript functions.

Output it somewhere suitable on your page.

javascript_for_client_init()

Returns JavaScript, including the <script>...</script> tags, which holds the function call to a function which initializes the menu. The function itself is included in the code returned by javascript_for_client_db().

Output it somewhere suitable on your page after you have output the string returned from javascript_for_db().

Calling this method is optional. If you do not call it, then calling the method javascript_for_client_on_load() is mandatory.

javascript_for_client_on_load()

Returns a string to be used as a <body> tag's onLoad event handler. It calls the function which initializes the menu. The function itself is included in the code returned by javascript_for_db().

Output it as part of the <body> tag. See examples/test-clientdb.cgi for an example.

Calling this method is optional. If you do not call it, then calling the method javascript_for_client_init() is mandatory.

new(%arg)

The constructor.

See the previous section for details of the parameters.

param($id)

Returns an array of database fields corresponding to the menu value chosen.

Call this to convert the value returned to the CGI script when the user selected a menu item, into the database fields which appeared in the second column of the table.

In other words, convert the first column of the SQL into the values of all the columns corresponding to that first column.

size()

Return the number of rows returned by your SQL.

Call this after calling 'table'.

It will tell you whether or not your menu is empty.

table()

Return the HTML for the table.

Sample Code ^

See examples/test-clientdb.cgi for a complete program.

You will need to run examples/bootstrap-menus.pl to load the 'test' database, 'campus' and 'unit' tables, with sample data.

You'll have to patch these 2 programs vis-a-vis the db vendor, username and password.

The sample data in bootstrap-menus.pl is simple, but is used by several modules, so don't be too keen on changing it :-).

See Also ^

        CGI::Explorer
        DBIx::HTML::LinkedMenus
        DBIx::HTML::PopupRadio

Author ^

DBIx::HTML::ClientDB was written by Ron Savage <ron@savage.net.au> in 2002.

Home page: http://savage.net.au/index.html

Copyright ^

Australian copyright (c) 2002, Ron Savage. All Programs of mine are 'OSI Certified Open Source Software'; you can redistribute them and/or modify them under the terms of The Artistic License, a copy of which is available at: http://www.opensource.org/licenses/index.html

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