


Introducing the Factory Pattern in PHP Design Patterns_PHP Tutorial
Question
How can you create such a "complex" object easily and conveniently without pasting and copying during operation?
Solution
Create a factory (a function or a class method) to create new objects. To understand the usefulness of factories, imagine the following differences...
code:
$connection =& new MySqlConnection($user, $password, $database);
... Make your code scalable and more concise...
$connection =& create_connection();
The latter The code snippets focus on the create_connect() factory that connects to the database. As just mentioned, the process of creating a database connection becomes a simple operation - just like the new operation. The advantage of the factory pattern lies in creating objects. Its task is to encapsulate the object creation process and then return a required new class.
Want to change the structure of the object and the way to create the object? You only need to select the object factory and change the code only once. (The function of the factory pattern is so powerful, it is at the bottom of the application, so it will continue to appear in many other complex patterns and applications.)
Sample Code
Factory Pattern Encapsulates the object creation process. You can create an object factory on the object itself or an additional factory class - it depends on your specific application. Let's look at an example of a factory object.
We found that in the following code, the database connection part appears repeatedly:
// PHP4
class Product {
function getList() { $db =& new MysqlConnection(DB_USER, DB_PW, DB_NAME);
//...
}
function getByName($name) { $db =& new MysqlConnection(DB_USER, DB_PW, DB_NAME);
//...
}
//...
}
You can easily change the parameters for connecting to the database, but you cannot increase or change the order of these parameters unless you change all the connection code.
You cannot easily instantiate a new class to connect to another database, such as PostgresqlConnection.
This makes it difficult to test and verify the state of the connection object alone.
Using the factory design pattern, the code will be greatly improved:
class Product {
function getList() {
$db =& $this->_getConnection();
//...
}
function &_getConnection() {
return new MysqlConnection (DB_USER, DB_PW, DB_NAME); on the _getConnection() method.
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