Php object-oriented advanced-magic methods and iterators, php object-oriented magic

Php object-oriented advanced-magic methods and iterators, php object-oriented magic

1. Magic Methods _ set and _ get, _ call

> These magic methods will be called when the relevant property or method does not exist.

> Function prototype

. Function _ set ($ property, $ value): Pass the attribute name and the new value

. Function _ get ($ property): Pass the property name and return the property value.

. Function _ call ($ methods, $ args): name of the method passed and an array of numeric indexes. The array contains the passed parameters. The index of the first parameter is 0.

1 class Coordinate {2 private $ arr = array ('x' => null, 'y' => null); 3 function _ get ($ property) {4 if (array_key_exists ($ property, $ this-> arr) {5 return $ this-> arr [$ property]; 6} else {7 print "a nonexistent key name cannot be accessed ". PHP_EOL; 8} 9} 10 function _ set ($ property, $ value) {11 if (array_key_exists ($ property, $ this-> arr )) {12 $ this-> arr [$ property] = $ value; 13} else {14 print "a nonexistent key name cannot be set ". PHP_EOL; 15} 16} 17} 18 19 $ obj = new Coordinate (); 20 $ obj-> x = 10; 21 echo $ obj-> x. PHP_EOL; 22 $ obj-> n = 20; 23 echo $ obj-> n. PHP_EOL;

2 ,__ call Application

> With _ call, the HelloWorldDelegator instance can call any existing methods of HelloWorld.

 1 class HelloWorld { 2         function display( $count ){ 3             for( $i = 0 ; $i < $count; $i++ ) { 4                 echo "Hello World $i " . PHP_EOL; 5             } 6             return $count; 7         } 8     } 9 10     11     class HelloWorldDelegator {12         private $obj;13         function __construct(){14             $this->obj = new HelloWorld();15         }16         function __call( $method, $args ) {17             return call_user_func_array( array( $this->obj, $method ), $args );18         }19     }20 21     $obj = new HelloWorldDelegator();22     print $obj->display( 3 );23     print PHP_EOL;24     25     $obj->show();

3. Iteration

> Implement an Iterator of your own. You can implement the Iterator interface.

Iterator interface prototype:

Iterator extends Traversable {/* Methods */abstract public mixed current ( void )abstract public scalar key ( void )abstract public void next ( void )abstract public void rewind ( void )abstract public bool valid ( void )}

 1 class NumberSquared implements Iterator { 2     private $start; 3     private $end; 4     private $cur; 5  6     function __construct ( $start, $end ){ 7         $this->start = $start; 8         $this->end = $end; 9     }10     function rewind(){ 11         $this->cur = $this->start;12     }13     function key(){14         return $this->cur;15     }16     function current(){17         return pow( $this->cur, 2 );18     }19     function next(){20         $this->cur++;21     }22     function valid(){23         return $this->cur <= $this->end;24     }25 }    26 27 $obj = new NumberSquared( 3, 9 );28 foreach( $obj as $key => $value ){29     print "the square of $key is $value" . PHP_EOL;30 }

The class itself is generally used to represent the data and the method of interaction with the data. Therefore, a pure class iterator is generally not required. We can implement another interface: IteratorAggregate. The abstract of the interface is as follows:

IteratorAggregate extends Traversable {/* Methods */abstract public Traversable getIterator ( void )}

This interface has only one method to create an external iterator interface.

After the transformation, the iterator and data processing are separated:

 1 class NumberSquared implements IteratorAggregate { 2     private $start; 3     private $end; 4  5     function __construct( $start, $end ) { 6         $this->start = $start; 7         $this->end = $end; 8     } 9 10     function getIterator(){11         return new NumberSquaredIterator( $this );12     }    13 14     function getStart(){15         return $this->start;16     }17 18     function getEnd(){ 19         return $this->end;20     }21 }22 23 class NumberSquaredIterator implements Iterator {24     private $cur;25     private $obj;26     function __construct( $obj ) {27         $this->obj = $obj;28     }29     function rewind(){ 30         $this->cur = $this->obj->getStart();31     }32     function key(){33         return $this->cur;34     }35     function next(){36         $this->cur++;37     }38     function current(){39         return pow( $this->cur, 2 );40     }41     function valid(){42         return $this->cur <= $this->obj->getEnd();43     }44 }45 46 $obj = new NumberSquared( 3, 9 );47 foreach( $obj as $key => $value ) {48     print "the $key is $value " . PHP_EOL;49 }