Loader Class
************

Loader, as the name suggests, is used to load elements. These elements
can be libraries (classes) View files, Drivers, Helpers, Models, or
your own files.

Note:

  This class is initialized automatically by the system so there is no
  need to do it manually.

* Application “Packages”

  * Package view files

* Class Reference


Application “Packages”
======================

An application package allows for the easy distribution of complete
sets of resources in a single directory, complete with its own
libraries, models, helpers, config, and language files. It is
recommended that these packages be placed in the
application/third_party directory. Below is a sample map of an package
directory.

The following is an example of a directory for an application package
named “Foo Bar”.

   /application/third_party/foo_bar

   config/
   helpers/
   language/
   libraries/
   models/

Whatever the purpose of the “Foo Bar” application package, it has its
own config files, helpers, language files, libraries, and models. To
use these resources in your controllers, you first need to tell the
Loader that you are going to be loading resources from a package, by
adding the package path via the "add_package_path()" method.


Package view files
------------------

By Default, package view files paths are set when "add_package_path()"
is called. View paths are looped through, and once a match is
encountered that view is loaded.

In this instance, it is possible for view naming collisions within
packages to occur, and possibly the incorrect package being loaded. To
ensure against this, set an optional second parameter of FALSE when
calling "add_package_path()".

   $this->load->add_package_path(APPPATH.'my_app', FALSE);
   $this->load->view('my_app_index'); // Loads
   $this->load->view('welcome_message'); // Will not load the default welcome_message b/c the second param to add_package_path is FALSE

   // Reset things
   $this->load->remove_package_path(APPPATH.'my_app');

   // Again without the second parameter:
   $this->load->add_package_path(APPPATH.'my_app');
   $this->load->view('my_app_index'); // Loads
   $this->load->view('welcome_message'); // Loads


Class Reference
===============

class CI_Loader

   library($library[, $params = NULL[, $object_name = NULL]])

      Parameters:
         * **$library** ("mixed") – Library name as a string or an
           array with multiple libraries

         * **$params** ("array") – Optional array of parameters to
           pass to the loaded library’s constructor

         * **$object_name** ("string") – Optional object name to
           assign the library to

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      This method is used to load core classes.

      Note:

        We use the terms “class” and “library” interchangeably.

      For example, if you would like to send email with CodeIgniter,
      the first step is to load the email class within your
      controller:

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

      Once loaded, the library will be ready for use, using
      "$this->email".

      Library files can be stored in subdirectories within the main
      “libraries” directory, or within your personal
      *application/libraries* directory. To load a file located in a
      subdirectory, simply include the path, relative to the
      “libraries” directory. For example, if you have file located at:

         libraries/flavors/Chocolate.php

      You will load it using:

         $this->load->library('flavors/chocolate');

      You may nest the file in as many subdirectories as you want.

      Additionally, multiple libraries can be loaded at the same time
      by passing an array of libraries to the load method.

         $this->load->library(array('email', 'table'));

      **Setting options**

      The second (optional) parameter allows you to optionally pass
      configuration setting. You will typically pass these as an
      array:

         $config = array (
                 'mailtype' => 'html',
                 'charset'  => 'utf-8',
                 'priority' => '1'
         );

         $this->load->library('email', $config);

      Config options can usually also be set via a config file. Each
      library is explained in detail in its own page, so please read
      the information regarding each one you would like to use.

      Please take note, when multiple libraries are supplied in an
      array for the first parameter, each will receive the same
      parameter information.

      **Assigning a Library to a different object name**

      If the third (optional) parameter is blank, the library will
      usually be assigned to an object with the same name as the
      library. For example, if the library is named Calendar, it will
      be assigned to a variable named "$this->calendar".

      If you prefer to set your own class names you can pass its value
      to the third parameter:

         $this->load->library('calendar', NULL, 'my_calendar');

         // Calendar class is now accessed using:
         $this->my_calendar

      Please take note, when multiple libraries are supplied in an
      array for the first parameter, this parameter is discarded.

   driver($library[, $params = NULL[, $object_name]])

      Parameters:
         * **$library** ("mixed") – Library name as a string or an
           array with multiple libraries

         * **$params** ("array") – Optional array of parameters to
           pass to the loaded library’s constructor

         * **$object_name** ("string") – Optional object name to
           assign the library to

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      This method is used to load driver libraries, acts very much
      like the "library()" method.

      As an example, if you would like to use sessions with
      CodeIgniter, the first step is to load the session driver within
      your controller:

         $this->load->driver('session');

      Once loaded, the library will be ready for use, using
      "$this->session".

      Driver files must be stored in a subdirectory within the main
      “libraries” directory, or within your personal
      *application/libraries* directory. The subdirectory must match
      the parent class name. Read the Drivers description for details.

      Additionally, multiple driver libraries can be loaded at the
      same time by passing an array of drivers to the load method.

         $this->load->driver(array('session', 'cache'));

      **Setting options**

      The second (optional) parameter allows you to optionally pass
      configuration settings. You will typically pass these as an
      array:

         $config = array(
                 'sess_driver' => 'cookie',
                 'sess_encrypt_cookie'  => true,
                 'encryption_key' => 'mysecretkey'
         );

         $this->load->driver('session', $config);

      Config options can usually also be set via a config file. Each
      library is explained in detail in its own page, so please read
      the information regarding each one you would like to use.

      **Assigning a Driver to a different object name**

      If the third (optional) parameter is blank, the library will be
      assigned to an object with the same name as the parent class.
      For example, if the library is named Session, it will be
      assigned to a variable named "$this->session".

      If you prefer to set your own class names you can pass its value
      to the third parameter:

         $this->load->library('session', '', 'my_session');

         // Session class is now accessed using:
         $this->my_session

   view($view[, $vars = array()[, return = FALSE]])

      Parameters:
         * **$view** ("string") – View name

         * **$vars** ("array") – An associative array of variables

         * **$return** ("bool") – Whether to return the loaded view

      Returns:
         View content string if $return is set to TRUE, otherwise
         CI_Loader instance (method chaining)

      Return type:
         "mixed"

      This method is used to load your View files. If you haven’t read
      the Views section of the user guide it is recommended that you
      do since it shows you how this method is typically used.

      The first parameter is required. It is the name of the view file
      you would like to load.

      Note:

        The .php file extension does not need to be specified unless
        you use something other than .php.

      The second **optional** parameter can take an associative array
      or an object as input, which it runs through the PHP extract()
      function to convert to variables that can be used in your view
      files. Again, read the Views page to learn how this might be
      useful.

      The third **optional** parameter lets you change the behavior of
      the method so that it returns data as a string rather than
      sending it to your browser. This can be useful if you want to
      process the data in some way. If you set the parameter to TRUE
      (boolean) it will return data. The default behavior is FALSE,
      which sends it to your browser. Remember to assign it to a
      variable if you want the data returned:

         $string = $this->load->view('myfile', '', TRUE);

   vars($vars[, $val = ''])

      Parameters:
         * **$vars** ("mixed") – An array of variables or a single
           variable name

         * **$val** ("mixed") – Optional variable value

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      This method takes an associative array as input and generates
      variables using the PHP extract() function. This method produces
      the same result as using the second parameter of the
      "$this->load->view()" method above. The reason you might want to
      use this method independently is if you would like to set some
      global variables in the constructor of your controller and have
      them become available in any view file loaded from any method.
      You can have multiple calls to this method. The data get cached
      and merged into one array for conversion to variables.

   get_var($key)

      Parameters:
         * **$key** ("string") – Variable name key

      Returns:
         Value if key is found, NULL if not

      Return type:
         "mixed"

      This method checks the associative array of variables available
      to your views. This is useful if for any reason a var is set in
      a library or another controller method using
      "$this->load->vars()".

   get_vars()

      Returns:
         An array of all assigned view variables

      Return type:
         "array"

      This method retrieves all variables available to your views.

   clear_vars()

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      Clears cached view variables.

   model($model[, $name = ''[, $db_conn = FALSE]])

      Parameters:
         * **$model** ("mixed") – Model name or an array containing
           multiple models

         * **$name** ("string") – Optional object name to assign the
           model to

         * **$db_conn** ("string") – Optional database configuration
           group to load

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

         $this->load->model('model_name');

      If your model is located in a subdirectory, include the relative
      path from your models directory. For example, if you have a
      model located at *application/models/blog/Queries.php* you’ll
      load it using:

         $this->load->model('blog/queries');

      If you would like your model assigned to a different object name
      you can specify it via the second parameter of the loading
      method:

         $this->load->model('model_name', 'fubar');
         $this->fubar->method();

   database([$params = ''[, $return = FALSE[, $query_builder = NULL]]])

      Parameters:
         * **$params** ("mixed") – Database group name or
           configuration options

         * **$return** ("bool") – Whether to return the loaded
           database object

         * **$query_builder** ("bool") – Whether to load the Query
           Builder

      Returns:
         Loaded CI_DB instance or FALSE on failure if $return is set
         to TRUE, otherwise CI_Loader instance (method chaining)

      Return type:
         "mixed"

      This method lets you load the database class. The two parameters
      are **optional**. Please see the database section for more info.

   dbforge([$db = NULL[, $return = FALSE]])

      Parameters:
         * **$db** ("object") – Database object

         * **$return** ("bool") – Whether to return the Database Forge
           instance

      Returns:
         Loaded CI_DB_forge instance if $return is set to TRUE,
         otherwise CI_Loader instance (method chaining)

      Return type:
         "mixed"

      Loads the Database Forge class, please refer to that manual for
      more info.

   dbutil([$db = NULL[, $return = FALSE]])

      Parameters:
         * **$db** ("object") – Database object

         * **$return** ("bool") – Whether to return the Database
           Utilities instance

      Returns:
         Loaded CI_DB_utility instance if $return is set to TRUE,
         otherwise CI_Loader instance (method chaining)

      Return type:
         "mixed"

      Loads the Database Utilities class, please refer to that manual
      for more info.

   helper($helpers)

      Parameters:
         * **$helpers** ("mixed") – Helper name as a string or an
           array containing multiple helpers

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      This method loads helper files, where file_name is the name of
      the file, without the _helper.php extension.

   file($path[, $return = FALSE])

      Parameters:
         * **$path** ("string") – File path

         * **$return** ("bool") – Whether to return the loaded file

      Returns:
         File contents if $return is set to TRUE, otherwise CI_Loader
         instance (method chaining)

      Return type:
         "mixed"

      This is a generic file loading method. Supply the filepath and
      name in the first parameter and it will open and read the file.
      By default the data is sent to your browser, just like a View
      file, but if you set the second parameter to boolean TRUE it
      will instead return the data as a string.

   language($files[, $lang = ''])

      Parameters:
         * **$files** ("mixed") – Language file name or an array of
           multiple language files

         * **$lang** ("string") – Language name

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      This method is an alias of the language loading method:
      "$this->lang->load()".

   config($file[, $use_sections = FALSE[, $fail_gracefully = FALSE]])

      Parameters:
         * **$file** ("string") – Configuration file name

         * **$use_sections** ("bool") – Whether configuration values
           should be loaded into their own section

         * **$fail_gracefully** ("bool") – Whether to just return
           FALSE in case of failure

      Returns:
         TRUE on success, FALSE on failure

      Return type:
         "bool"

      This method is an alias of the config file loading method:
      "$this->config->load()"

   is_loaded($class)

      Parameters:
         * **$class** ("string") – Class name

      Returns:
         Singleton property name if found, FALSE if not

      Return type:
         "mixed"

      Allows you to check if a class has already been loaded or not.

      Note:

        The word “class” here refers to libraries and drivers.

      If the requested class has been loaded, the method returns its
      assigned name in the CI Super-object and FALSE if it’s not:

         $this->load->library('form_validation');
         $this->load->is_loaded('Form_validation');      // returns 'form_validation'

         $this->load->is_loaded('Nonexistent_library');  // returns FALSE

      Important:

        If you have more than one instance of a class (assigned to
        different properties), then the first one will be returned.

         $this->load->library('form_validation', $config, 'fv');
         $this->load->library('form_validation');

         $this->load->is_loaded('Form_validation');      // returns 'fv'

   add_package_path($path[, $view_cascade = TRUE])

      Parameters:
         * **$path** ("string") – Path to add

         * **$view_cascade** ("bool") – Whether to use cascading views

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      Adding a package path instructs the Loader class to prepend a
      given path for subsequent requests for resources. As an example,
      the “Foo Bar” application package above has a library named
      Foo_bar.php. In our controller, we’d do the following:

         $this->load->add_package_path(APPPATH.'third_party/foo_bar/')
                 ->library('foo_bar');

   remove_package_path([$path = ''])

      Parameters:
         * **$path** ("string") – Path to remove

      Returns:
         CI_Loader instance (method chaining)

      Return type:
         "CI_Loader"

      When your controller is finished using resources from an
      application package, and particularly if you have other
      application packages you want to work with, you may wish to
      remove the package path so the Loader no longer looks in that
      directory for resources. To remove the last path added, simply
      call the method with no parameters.

      Or to remove a specific package path, specify the same path
      previously given to "add_package_path()" for a package.:

         $this->load->remove_package_path(APPPATH.'third_party/foo_bar/');

   get_package_paths([$include_base = TRUE])

      Parameters:
         * **$include_base** ("bool") – Whether to include BASEPATH

      Returns:
         An array of package paths

      Return type:
         "array"

      Returns all currently available package paths.
