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The output is in .NET Add Code39 in .NET The output is

The output is use visual studio .net code 39 full ascii generating tomake code 39 in .net bar code 39 1 Error: Can"t write a property other than x & y Error: Can"t read a property other than x & y As x exists in the object s a rray, the setter and getter method handlers agrees to read/write the values. However, when accessing the property n, both for reading and writing, array_key_exists() returns false and, therefore, the error messages are reached..

Gutmans_ch04 Page 87 Thursday, September 23, 2004 2:39 PM 4.2 Overloading Capabilities __call() can be used for a va .net framework 39 barcode riety of purposes. The following example shows how to create a delegation model, in which an instance of the class HelloWorldDelegator delegates all method calls to an instance of the HelloWorld class: class HelloWorld { function display($count) { for ($i = 0; $i < $count; $i++) { print "Hello, World\n"; } return $count; } } class HelloWorldDelegator { function __construct() { $this->obj = new HelloWorld(); } function __call($method, $args) { return call_user_func_array(array($this->obj , $method), $args); } private $obj; } $obj = new HelloWorldDelegator(); print $obj->display(3);.

This script s output is Hello, World Hello, World Hello, World 3 The call_user_func_array() fu nction allows __call() to relay the function call with its arguments to HelloWorld::display() which prints out "Hello, World\n" three times. It then returns $count (in this case, 3 ) which is then printed out. Not only can you relay the method call to a different object (or handle it in whatever way you want), but you can also return a value from __call(), just like a regular method.

. Gutmans_ch04 Page 88 Thursday, September 23, 2004 2:39 PM PHP 5 Advanced OOP and Design Patterns Chap. 4 4.2.2 Overloading the Array A ccess Syntax It is common to have key/value mappings or, in other words, lookup dictionaries in your application framework.

For this purpose, PHP supports associative arrays that map either integer or string values to any other PHP value. This feature was covered in 2, PHP 5 Basic Language, and in case you forgot about it, here s an example that looks up the user John s socialsecurity number using an associative array which holds this information:. print "John"s ID number is " Code 39 for .NET . $userMap["John"];.

Associative arrays are extrem ely convenient when you have all the information at hand. But consider a government of ce that has millions of people in its database; it just wouldn t make sense to load the entire database into the $userMap associative array just to look up one user. A possible alternative is to write a method that will look up the user s id number via a database call.

The previous code would look something like the following:. print "John"s ID number is " Code-39 for .NET . $db->FindIDNumber("John");.

This example would work well, but many developers prefer the associative array syntax to access key/value-like dictionaries. For this purpose, PHP 5 enables you to overload an object so that it can behave like an array. Basically, it would enable you to use the array syntax, but behind the scenes, a method written by you would be called, which would execute the relevant database call, returning the wanted value.

It is really a matter of personal preference as to what method to use. Sometimes, it is nicer to use this overloading ability than the verbosity of calling a method, and it s up to you to decide which method suits you best. To allow your class to overload the array syntax, it needs to implement the ArrayAccess interface (see Figure 4.

1).. interface ArrayAccess bool offsetExists($index) mix ed offsetGet($index) void offsetSet($index,$new_value) void offsetUnset($index). Fig. 4.1 ArrayAccess interface. Gutmans_ch04 Page 89 Thursday, September 23, 2004 2:39 PM 4.3 Iterators The following example shows h ow to use it. It is incomplete because the database methods themselves aren t implemented:. class UserToSocialSecurity im visual .net 3 of 9 barcode plements ArrayAccess { private $db; // An object which includes database access methods function offsetExists($name) { return $this->db->userExists($name); } function offsetGet($name) { return $this->db->getUserId($name); } function offsetSet($name, $id) { $this->db->setUserId($name, $id); } function offsetUnset($name) { $this->db->removeUser($name); } } $userMap = new UserToSocialSecurity(); print "John"s ID number is " . $userMap["John"];.

You can see that the object $ userMap is used just like an array, but behind the scenes, when the $userMap["John"] lookup is performed, the offsetGet() method is invoked, which in turn calls the database getUserId() method..
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