From 8ede1a2ecbb62577afd32996956c5feaf7ddf9b6 Mon Sep 17 00:00:00 2001 From: Derek Jones Date: Wed, 5 Oct 2011 13:34:52 -0500 Subject: replacing the old HTML user guide with a Sphinx-managed user guide --- user_guide_src/source/general/helpers.rst | 123 ++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 user_guide_src/source/general/helpers.rst (limited to 'user_guide_src/source/general/helpers.rst') diff --git a/user_guide_src/source/general/helpers.rst b/user_guide_src/source/general/helpers.rst new file mode 100644 index 000000000..2b113c1f4 --- /dev/null +++ b/user_guide_src/source/general/helpers.rst @@ -0,0 +1,123 @@ +################ +Helper Functions +################ + +Helpers, as the name suggests, help you with tasks. Each helper file is +simply a collection of functions in a particular category. There are URL +Helpers, that assist in creating links, there are Form Helpers that help +you create form elements, Text Helpers perform various text formatting +routines, Cookie Helpers set and read cookies, File Helpers help you +deal with files, etc. + +Unlike most other systems in CodeIgniter, Helpers are not written in an +Object Oriented format. They are simple, procedural functions. Each +helper function performs one specific task, with no dependence on other +functions. + +CodeIgniter does not load Helper Files by default, so the first step in +using a Helper is to load it. Once loaded, it becomes globally available +in your :doc:`controller <../general/controllers>` and +:doc:`views <../general/views>`. + +Helpers are typically stored in your system/helpers, or +application/helpers directory. CodeIgniter will look first in your +application/helpers directory. If the directory does not exist or the +specified helper is not located there CI will instead look in your +global system/helpers folder. + +Loading a Helper +================ + +Loading a helper file is quite simple using the following function:: + + $this->load->helper('name'); + +Where name is the file name of the helper, without the .php file +extension or the "helper" part. + +For example, to load the URL Helper file, which is named +url_helper.php, you would do this:: + + $this->load->helper('url'); + +A helper can be loaded anywhere within your controller functions (or +even within your View files, although that's not a good practice), as +long as you load it before you use it. You can load your helpers in your +controller constructor so that they become available automatically in +any function, or you can load a helper in a specific function that needs +it. + +Note: The Helper loading function above does not return a value, so +don't try to assign it to a variable. Just use it as shown. + +Loading Multiple Helpers +======================== + +If you need to load more than one helper you can specify them in an +array, like this:: + + $this->load->helper( array('helper1', 'helper2', 'helper3') ); + +Auto-loading Helpers +==================== + +If you find that you need a particular helper globally throughout your +application, you can tell CodeIgniter to auto-load it during system +initialization. This is done by opening the +application/config/autoload.php file and adding the helper to the +autoload array. + +Using a Helper +============== + +Once you've loaded the Helper File containing the function you intend to +use, you'll call it the way you would a standard PHP function. + +For example, to create a link using the anchor() function in one of your +view files you would do this:: + + + +Where "Click Here" is the name of the link, and "blog/comments" is the +URI to the controller/function you wish to link to. + +"Extending" Helpers +=================== + +To "extend" Helpers, create a file in your application/helpers/ folder +with an identical name to the existing Helper, but prefixed with MY\_ +(this item is configurable. See below.). + +If all you need to do is add some functionality to an existing helper - +perhaps add a function or two, or change how a particular helper +function operates - then it's overkill to replace the entire helper with +your version. In this case it's better to simply "extend" the Helper. +The term "extend" is used loosely since Helper functions are procedural +and discrete and cannot be extended in the traditional programmatic +sense. Under the hood, this gives you the ability to add to the +functions a Helper provides, or to modify how the native Helper +functions operate. + +For example, to extend the native Array Helper you'll create a file +named application/helpers/MY_array_helper.php, and add or override +functions:: + + // any_in_array() is not in the Array Helper, so it defines a new function function any_in_array($needle, $haystack) {     $needle = (is_array($needle)) ? $needle : array($needle);     foreach ($needle as $item)     {         if (in_array($item, $haystack))         {             return TRUE;         }         }     return FALSE; } // random_element() is included in Array Helper, so it overrides the native function function random_element($array) {     shuffle($array);     return array_pop($array); } + +Setting Your Own Prefix +----------------------- + +The filename prefix for "extending" Helpers is the same used to extend +libraries and Core classes. To set your own prefix, open your +application/config/config.php file and look for this item:: + + $config['subclass_prefix'] = 'MY_'; + +Please note that all native CodeIgniter libraries are prefixed with CI\_ +so DO NOT use that as your prefix. + +Now What? +========= + +In the Table of Contents you'll find a list of all the available Helper +Files. Browse each one to see what they do. -- cgit v1.2.3-24-g4f1b