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          * Values in the arguments collection which are Closure instances will be
  39          * expanded by invoking them with no arguments before passing the
  40          * resulting value on to the constructor/callable. This can be used to
  41          * pass IDatabase instances or other live objects to the
  42          * constructor/callable. This behavior can be suppressed by adding
  43          * closure_expansion => false to the specification.
  44          *
  45          * The specification may also contain a 'calls' key that describes method
  46          * calls to make on the newly created object before returning it. This
  47          * pattern is often known as "setter injection". The value of this key is
  48          * expected to be an associative array with method names as keys and
  49          * argument lists as values. The argument list will be expanded (or not)
  50          * in the same way as the 'args' key for the main object.
  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                 $expandArgs = !isset( $spec['closure_expansion'] ) ||
  62                         $spec['closure_expansion'] === true;
  63
  64                 if ( $expandArgs ) {
  65                         $args = static::expandClosures( $args );
  66                 }
  67
  68                 if ( isset( $spec['class'] ) ) {
  69                         $clazz = $spec['class'];
  70                         if ( !$args ) {
  71                                 $obj = new $clazz();
  72                         } else {
  73                                 $obj = static::constructClassInstance( $clazz, $args );
  74                         }
  75                 } elseif ( isset( $spec['factory'] ) ) {
  76                         $obj = call_user_func_array( $spec['factory'], $args );
  77                 } else {
  78                         throw new InvalidArgumentException(
  79                                 'Provided specification lacks both factory and class parameters.'
  80                         );
  81                 }
  82
  83                 if ( isset( $spec['calls'] ) && is_array( $spec['calls'] ) ) {
  84                         // Call additional methods on the newly created object
  85                         foreach ( $spec['calls'] as $method => $margs ) {
  86                                 if ( $expandArgs ) {
  87                                         $margs = static::expandClosures( $margs );
  88                                 }
  89                                 call_user_func_array( array( $obj, $method ), $margs );
  90                         }
  91                 }
  92
  93                 return $obj;
  94         }
  95
  96         /**
  97          * Iterate a list and call any closures it contains.
  98          *
  99          * @param array $list List of things
 100          * @return array List with any Closures replaced with their output
 101          */
 102         protected static function expandClosures( $list ) {
 103                 return array_map( function ( $value ) {
 104                         if ( is_object( $value ) && $value instanceof Closure ) {
 105                                 // If $value is a Closure, call it.
 106                                 return $value();
 107                         } else {
 108                                 return $value;
 109                         }
 110                 }, $list );
 111         }
 112
 113         /**
 114          * Construct an instance of the given class using the given arguments.
 115          *
 116          * PHP's `call_user_func_array()` doesn't work with object construction so
 117          * we have to use other measures. Starting with PHP 5.6.0 we could use the
 118          * "splat" operator (`...`) to unpack the array into an argument list.
 119          * Sadly there is no way to conditionally include a syntax construct like
 120          * a new operator in a way that allows older versions of PHP to still
 121          * parse the file. Instead, we will try a loop unrolling technique that
 122          * works for 0-10 arguments. If we are passed 11 or more arguments we will
 123          * take the performance penalty of using
 124          * `ReflectionClass::newInstanceArgs()` to construct the desired object.
 125          *
 126          * @param string $clazz Class name
 127          * @param array $args Constructor arguments
 128          * @return mixed Constructed instance
 129          */
 130         public static function constructClassInstance( $clazz, $args ) {
 131                 // TODO: when PHP min version supported is >=5.6.0 replace this
 132                 // function body with `return new $clazz( ... $args );`.
 133                 $obj = null;
 134                 switch ( count( $args ) ) {
 135                         case 0:
 136                                 $obj = new $clazz();
 137                                 break;
 138                         case 1:
 139                                 $obj = new $clazz( $args[0] );
 140                                 break;
 141                         case 2:
 142                                 $obj = new $clazz( $args[0], $args[1] );
 143                                 break;
 144                         case 3:
 145                                 $obj = new $clazz( $args[0], $args[1], $args[2] );
 146                                 break;
 147                         case 4:
 148                                 $obj = new $clazz( $args[0], $args[1], $args[2], $args[3] );
 149                                 break;
 150                         case 5:
 151                                 $obj = new $clazz(
 152                                         $args[0], $args[1], $args[2], $args[3], $args[4]
 153                                 );
 154                                 break;
 155                         case 6:
 156                                 $obj = new $clazz(
 157                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 158                                         $args[5]
 159                                 );
 160                                 break;
 161                         case 7:
 162                                 $obj = new $clazz(
 163                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 164                                         $args[5], $args[6]
 165                                 );
 166                                 break;
 167                         case 8:
 168                                 $obj = new $clazz(
 169                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 170                                         $args[5], $args[6], $args[7]
 171                                 );
 172                                 break;
 173                         case 9:
 174                                 $obj = new $clazz(
 175                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 176                                         $args[5], $args[6], $args[7], $args[8]
 177                                 );
 178                                 break;
 179                         case 10:
 180                                 $obj = new $clazz(
 181                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 182                                         $args[5], $args[6], $args[7], $args[8], $args[9]
 183                                 );
 184                                 break;
 185                         default:
 186                                 // Fall back to using ReflectionClass and curse the developer
 187                                 // who decided that 11+ args was a reasonable method
 188                                 // signature.
 189                                 $ref = new ReflectionClass( $clazz );
 190                                 $obj = $ref->newInstanceArgs( $args );
 191                 }
 192                 return $obj;
 193         }
 194 }