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Object-Oriented Programming with PHP

Using the factory method pattern


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Object-Oriented Programming with PHP

with Jon Peck

Video: Using the factory method pattern

The second design pattern I am going to demonstrate is the factory method. The factory method is useful for creating objects without having to specify the class. Sound familiar? Let's look at the Address class. Open the Address class now, and take a look at the Load in Instance methods. In particular, notice the way that the returned address_type_id specifies the name of the class to be created in getInstance. However, as it's currently written, it will fail if it doesn't get the right address type. Let's improve on getInstance to throw an exception, instead of crashing out.
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  1. 4m 10s
    1. Welcome
      39s
    2. Exercise files
      2m 16s
    3. What you should know
      1m 15s
  2. 7m 47s
    1. What is an object?
      2m 6s
    2. What is a class?
      2m 7s
    3. Why should you use object-oriented programming?
      2m 14s
    4. The history of object-oriented PHP
      1m 20s
  3. 16m 40s
    1. Defining a class
      2m 58s
    2. Defining class properties
      3m 26s
    3. Creating a method and exploring object context with $this
      2m 50s
    4. Instantiating an object and accessing its contents
      3m 19s
    5. Specifying the visibility scope
      4m 7s
  4. 15m 51s
    1. What is a magic method, and do I need one?
      2m 23s
    2. Overloading property access
      6m 37s
    3. Customizing object construction
      4m 34s
    4. Standardizing object rendering as a string
      2m 17s
  5. 20m 54s
    1. Using the static keyword
      3m 36s
    2. Leveraging scope resolution operators
      1m 10s
    3. Setting constant values
      2m 47s
    4. Implementing static methods
      5m 43s
    5. Creating a database class
      7m 38s
  6. 26m 19s
    1. Extending your class
      6m 8s
    2. Abstracting classes
      5m 57s
    3. Sharing interfaces using polymorphism
      4m 39s
    4. Overriding methods, properties, and constants
      3m 25s
    5. Cloning and comparing objects
      2m 51s
    6. Referencing objects
      3m 19s
  7. 14m 52s
    1. Leveraging standard class objects
      2m 42s
    2. Retrieving objects from the database
      5m 41s
    3. Error handling with exceptions
      2m 6s
    4. Customizing PHP exceptions
      4m 23s
  8. 8m 2s
    1. Identifying the singleton pattern
      1m 42s
    2. Using the factory method pattern
      1m 51s
    3. Implementing a strategy pattern
      4m 29s
  9. 2m 57s
    1. Looking forward to namespaces
      47s
    2. Next steps
      1m 6s
    3. Goodbye
      1m 4s

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Object-Oriented Programming with PHP
1h 57m Intermediate Sep 26, 2012 Updated Apr 10, 2013

Viewers: in countries Watching now:

Whether you're enhancing or optimizing existing code or just starting from scratch, there's never a better time to start integrating object-oriented design techniques. This course shows how to integrate the principles of object-oriented programming into the build of a PHP-driven web page or application. After an overview of what objects and classes are and why they should be used, author Jon Peck dives into creating and instantiating objects, then defining the class relationships and interactions that will form the basis of your coding arsenal. The course also shows how to leverage PHP objects and implement design patterns, and looks at steps you can take to continue adding to your programming tool belt.

Topics include:
  • Historical overview of object-oriented PHP
  • Defining classes
  • Creating a method/object context with $this
  • Accessing classes without instantiation
  • Creating a database class
  • Extending and abstracting classes
  • Cloning and comparing objects
  • Error handling with exceptions
  • Implementing design patterns, such as the factory and strategy patterns
Subjects:
Developer Programming Languages
Software:
PHP
Author:
Jon Peck

Using the factory method pattern

The second design pattern I am going to demonstrate is the factory method. The factory method is useful for creating objects without having to specify the class. Sound familiar? Let's look at the Address class. Open the Address class now, and take a look at the Load in Instance methods. In particular, notice the way that the returned address_type_id specifies the name of the class to be created in getInstance. However, as it's currently written, it will fail if it doesn't get the right address type. Let's improve on getInstance to throw an exception, instead of crashing out.

First, create a new constant with an error code. Const ADDRESS_ERROR_UNKNOWN_SUBCLASS = 1001. I am going to go to the getInstance method, and add a check to see if the class exists, before I instantiate it. I'll use the class_exists method, which returns a boolean. If not (!class_exists [$class_name]), throw new ExceptionAddress ('Address_subclass not found, cannot create', self:: ADDRESS_ERROR_UNKNOWN_SUBCLASS); reading through it, if the class does not exist, throw a new exception address, along with the error code for unknown subclass. Save, then go to the demo source.

Instead of explicitly creating an address residence, use the factory method. Address::getInstance of (Address:: ADDRESS_TYPE_RESIDENCE); Save the demo, then return to your browser, and refresh. Everything should look the same. For further practice, switch the remaining explicit instantiations of address to use the factory method. Then, wrap the getInstance calls, and try catch blocks.

Find answers to the most frequently asked questions about Object-Oriented Programming with PHP.


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Q: I'm not seeing warnings or errors in my environment like the video; why not?
A: Your PHP configuration is probably configured not to show them to you. This is often true on commercial web hosts and is often the default. Fortunately, there are multiple ways of resolving this.

The easiest way would be to explicitly enable error reporting at the top of the PHP script you wish to debug.

error_reporting(E_ALL | E_STRICT);
ini_set('display_errors', 1);

Alternatively, if you have access to your php.ini file and you want to always have error reporting on, change error_reporting = to a development friendly value of

error_reporting = E_ALL | E_STRICT

then change display_errors = to

display_errors = On

Finally, if access to the php.ini file is not available, you can add the following directives to your .htaccess or VirtualHost configuration for Apache:

php_value error_reporting 32767
php_value display_errors 1

If you would like a development optimized development environment like the one utilized in this course, see Up and Running with Linux for PHP Developers, here in the lynda.com online training library.

Q: This course was updated on 4/10/2013. What changed?

A: The author rerecorded some of the tutorials to add more background information and better graphics.

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