Lazy Initialization Design Patterns in PHP
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Lazy Initialization Design Patterns in PHP

Lazy Initialization Design Patterns in PHP

Lazy Initialization Pattern

Lazy evaluation
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.
This is typically accomplished by maintaining a flag indicating whether the process has taken place. Each time the desired object is summoned, the flag is tested. If it is ready, it is returned. If not, it is initialized on the spot.

Lazy Initialization Method: problem & solution

Problem

Solution
  • You want to delay the creation of an instance or an expensive operation until the first time it is needed
  • You want the operation to be executed only when and if necessary
  • The Lazy Initialization pattern delays the creation of an object or the execution of an expensive process until the first time it is needed
 
<?php
 header('Content-type:text/plain; charset=utf-8');
 class Fruit {
 private $type;
 private static $types = array();
 private function __construct($type) {
 $this->type = $type;
 }
 public static function getFruit($type) {
 // Lazy initialization takes place here
 if (!array_key_exists($type, self::$types)) {
 self::$types[$type] = new Fruit($type);
 }
 return self::$types[$type];
 }
 public static function printCurrentTypes() {
 echo 'Number of instances made: ' . count(self::$types) . "\n";
 foreach (array_keys(self::$types) as $key) {
 echo "$key\n";
 }
 echo "\n";
 }
 }
 Fruit::getFruit('Apple');
 Fruit::printCurrentTypes();
 Fruit::getFruit('Banana');
 Fruit::printCurrentTypes();
 Fruit::getFruit('Mango');
 Fruit::printCurrentTypes();?>

OUTPUT:
Number of instances made: 1
Apple
Number of instances made: 2
Apple
Banana
Number of instances made: 3
Mango
Apple
Banana

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