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  * @copyright © 2014 Wikimedia Foundation and contributors
  25  */
  26 class ObjectFactory {
  27
  28         /**
  29          * Instantiate an object based on a specification array.
  30          *
  31          * The specification array must contain a 'class' key with string value
  32          * that specifies the class name to instantiate or a 'factory' key with
  33          * a callable (is_callable() === true). It can optionally contain
  34          * an 'args' key that provides arguments to pass to the
  35          * constructor/callable.
  36          *
  37          * Values in the arguments collection which are Closure instances will be
  38          * expanded by invoking them with no arguments before passing the
  39          * resulting value on to the constructor/callable. This can be used to
  40          * pass IDatabase instances or other live objects to the
  41          * constructor/callable. This behavior can be suppressed by adding
  42          * closure_expansion => false to the specification.
  43          *
  44          * The specification may also contain a 'calls' key that describes method
  45          * calls to make on the newly created object before returning it. This
  46          * pattern is often known as "setter injection". The value of this key is
  47          * expected to be an associative array with method names as keys and
  48          * argument lists as values. The argument list will be expanded (or not)
  49          * in the same way as the 'args' key for the main object.
  50          *
  51          * @param array $spec Object specification
  52          * @return object
  53          * @throws InvalidArgumentException when object specification does not
  54          * contain 'class' or 'factory' keys
  55          * @throws ReflectionException when 'args' are supplied and 'class'
  56          * constructor is non-public or non-existent
  57          */
  58         public static function getObjectFromSpec( $spec ) {
  59                 $args = isset( $spec['args'] ) ? $spec['args'] : [];
  60                 $expandArgs = !isset( $spec['closure_expansion'] ) ||
  61                         $spec['closure_expansion'] === true;
  62
  63                 if ( $expandArgs ) {
  64                         $args = static::expandClosures( $args );
  65                 }
  66
  67                 if ( isset( $spec['class'] ) ) {
  68                         $clazz = $spec['class'];
  69                         if ( !$args ) {
  70                                 $obj = new $clazz();
  71                         } else {
  72                                 $obj = static::constructClassInstance( $clazz, $args );
  73                         }
  74                 } elseif ( isset( $spec['factory'] ) ) {
  75                         $obj = call_user_func_array( $spec['factory'], $args );
  76                 } else {
  77                         throw new InvalidArgumentException(
  78                                 'Provided specification lacks both factory and class parameters.'
  79                         );
  80                 }
  81
  82                 if ( isset( $spec['calls'] ) && is_array( $spec['calls'] ) ) {
  83                         // Call additional methods on the newly created object
  84                         foreach ( $spec['calls'] as $method => $margs ) {
  85                                 if ( $expandArgs ) {
  86                                         $margs = static::expandClosures( $margs );
  87                                 }
  88                                 call_user_func_array( [ $obj, $method ], $margs );
  89                         }
  90                 }
  91
  92                 return $obj;
  93         }
  94
  95         /**
  96          * Iterate a list and call any closures it contains.
  97          *
  98          * @param array $list List of things
  99          * @return array List with any Closures replaced with their output
 100          */
 101         protected static function expandClosures( $list ) {
 102                 return array_map( function ( $value ) {
 103                         if ( is_object( $value ) && $value instanceof Closure ) {
 104                                 // If $value is a Closure, call it.
 105                                 return $value();
 106                         } else {
 107                                 return $value;
 108                         }
 109                 }, $list );
 110         }
 111
 112         /**
 113          * Construct an instance of the given class using the given arguments.
 114          *
 115          * PHP's `call_user_func_array()` doesn't work with object construction so
 116          * we have to use other measures. Starting with PHP 5.6.0 we could use the
 117          * "splat" operator (`...`) to unpack the array into an argument list.
 118          * Sadly there is no way to conditionally include a syntax construct like
 119          * a new operator in a way that allows older versions of PHP to still
 120          * parse the file. Instead, we will try a loop unrolling technique that
 121          * works for 0-10 arguments. If we are passed 11 or more arguments we will
 122          * take the performance penalty of using
 123          * `ReflectionClass::newInstanceArgs()` to construct the desired object.
 124          *
 125          * @param string $clazz Class name
 126          * @param array $args Constructor arguments
 127          * @return mixed Constructed instance
 128          */
 129         public static function constructClassInstance( $clazz, $args ) {
 130                 // $args should be a non-associative array; show nice error if that's not the case
 131                 if ( $args && array_keys( $args ) !== range( 0, count( $args ) - 1 ) ) {
 132                         throw new InvalidArgumentException( __METHOD__ . ': $args cannot be an associative array' );
 133                 }
 134
 135                 // TODO: when PHP min version supported is >=5.6.0 replace this
 136                 // with `return new $clazz( ... $args );`.
 137                 $obj = null;
 138                 switch ( count( $args ) ) {
 139                         case 0:
 140                                 $obj = new $clazz();
 141                                 break;
 142                         case 1:
 143                                 $obj = new $clazz( $args[0] );
 144                                 break;
 145                         case 2:
 146                                 $obj = new $clazz( $args[0], $args[1] );
 147                                 break;
 148                         case 3:
 149                                 $obj = new $clazz( $args[0], $args[1], $args[2] );
 150                                 break;
 151                         case 4:
 152                                 $obj = new $clazz( $args[0], $args[1], $args[2], $args[3] );
 153                                 break;
 154                         case 5:
 155                                 $obj = new $clazz(
 156                                         $args[0], $args[1], $args[2], $args[3], $args[4]
 157                                 );
 158                                 break;
 159                         case 6:
 160                                 $obj = new $clazz(
 161                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 162                                         $args[5]
 163                                 );
 164                                 break;
 165                         case 7:
 166                                 $obj = new $clazz(
 167                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 168                                         $args[5], $args[6]
 169                                 );
 170                                 break;
 171                         case 8:
 172                                 $obj = new $clazz(
 173                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 174                                         $args[5], $args[6], $args[7]
 175                                 );
 176                                 break;
 177                         case 9:
 178                                 $obj = new $clazz(
 179                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 180                                         $args[5], $args[6], $args[7], $args[8]
 181                                 );
 182                                 break;
 183                         case 10:
 184                                 $obj = new $clazz(
 185                                         $args[0], $args[1], $args[2], $args[3], $args[4],
 186                                         $args[5], $args[6], $args[7], $args[8], $args[9]
 187                                 );
 188                                 break;
 189                         default:
 190                                 // Fall back to using ReflectionClass and curse the developer
 191                                 // who decided that 11+ args was a reasonable method
 192                                 // signature.
 193                                 $ref = new ReflectionClass( $clazz );
 194                                 $obj = $ref->newInstanceArgs( $args );
 195                 }
 196                 return $obj;
 197         }
 198 }