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Using the factory method pattern

From: Object-Oriented Programming with PHP

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.

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.

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Object-Oriented Programming with PHP

37 video lessons · 17420 viewers

Jon Peck
Author

 
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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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