includes/libs/ObjectFactory.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @file
  19  */
  20
  21 /**
  22  * Construct objects from configuration instructions.
  23  *
  24  * @author Bryan Davis <bd808@wikimedia.org>
  25  * @copyright © 2014 Bryan Davis and Wikimedia Foundation.
  26  */
  27 class ObjectFactory {
  28
  29         /**
  30          * Instantiate an object based on a specification array.
  31          *
  32          * The specification array must contain a 'class' key with string value
  33          * that specifies the class name to instantiate or a 'factory' key with
  34          * a callable (is_callable() === true). It can optionally contain
  35          * an 'args' key that provides arguments to pass to the
  36          * constructor/callable.
  37          *
  38          * Object construction using a specification having both 'class' and
  39          * 'args' members will call the constructor of the class using
  40          * ReflectionClass::newInstanceArgs. The use of ReflectionClass carries
  41          * a performance penalty and should not be used to create large numbers of
  42          * objects. If this is needed, consider introducing a factory method that
  43          * can be called via call_user_func_array() instead.
  44          *
  45          * Values in the arguments collection which are Closure instances will be
  46          * expanded by invoking them with no arguments before passing the
  47          * resulting value on to the constructor/callable. This can be used to
  48          * pass DatabaseBase instances or other live objects to the
  49          * constructor/callable. This behavior can be suppressed by adding
  50          * closure_expansion => false to the specification.
  51          *
  52          * @param array $spec Object specification
  53          * @return object
  54          * @throws InvalidArgumentException when object specification does not
  55          * contain 'class' or 'factory' keys
  56          * @throws ReflectionException when 'args' are supplied and 'class'
  57          * constructor is non-public or non-existent
  58          */
  59         public static function getObjectFromSpec( $spec ) {
  60                 $args = isset( $spec['args'] ) ? $spec['args'] : array();
  61
  62                 if ( !isset( $spec['closure_expansion'] ) ||
  63                         $spec['closure_expansion'] === true
  64                 ) {
  65                         $args = array_map( function ( $value ) {
  66                                 if ( is_object( $value ) && $value instanceof Closure ) {
  67                                         // If an argument is a Closure, call it.
  68                                         return $value();
  69                                 } else {
  70                                         return $value;
  71                                 }
  72                         }, $args );
  73                 }
  74
  75                 if ( isset( $spec['class'] ) ) {
  76                         $clazz = $spec['class'];
  77                         if ( !$args ) {
  78                                 $obj = new $clazz();
  79                         } else {
  80                                 $ref = new ReflectionClass( $clazz );
  81                                 $obj = $ref->newInstanceArgs( $args );
  82                         }
  83                 } elseif ( isset( $spec['factory'] ) ) {
  84                         $obj = call_user_func_array( $spec['factory'], $args );
  85                 } else {
  86                         throw new InvalidArgumentException(
  87                                 'Provided specification lacks both factory and class parameters.'
  88                         );
  89                 }
  90
  91                 return $obj;
  92         }
  93 }