� � CMP-3110 ~ E-Commerce Applications Development

Lecture 02

Planning Our Framework

Framework

• Definition
• a basic structure underlying a system, concept, or text.
• In general, a framework is a real or conceptual structure intended to serve as a support or guide for the building of something that expands the structure into something useful.

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Patterns

• Definition
• a design pattern is a general repeatable solution to a commonly occurring problem in software design.
•  A design pattern isn't a finished design that can be transformed directly into code
• Uses of Design Patterns
• speed up the development process
• providing tested, proven development paradigms

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Patterns

Which patterns will be used?

• Model-View-Controller (MVC)
• Registry
• Singleton

Model-View-Controller (MVC)

• Model 
• Represents an object. It can also have logic to update controller if its data changes.
• View 
• Represents the visualization of the data that model contains.
• Controller 
• Acts on both model and view. It controls the data flow into model object and updates the view whenever data changes. It keeps view and model separate.

Model-View-Controller (MVC)

Model-View-Controller (MVC)

Model-View-Controller (MVC)

Reference: Software Engineering by Ian Summerville – 9^th edition

Registry

• Provides a means to store a collection of objects within our framework (Container of objects for reuse).

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• Each set of controllers and models we create need to perform some shared tasks, including:
• Querying the database
• Checking if the user is logged in, and if so, getting certain user data
• Sending data to the views to be generated (template management)
• Sending e-mails, for instance to confirm a purchase with the customer
• Interacting with the server's filesystem, for instance to upload photographs of products

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Registry

Singleton

• Restrict an object to one instance only

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• However, we will use it to ensure we have only one instance of our registry available in the framework at any point of time.

File/Folder Structure

Building a Framework

Pattern Implementation: MVC

Pattern Implementation: Registry�

• Needs
• It needs to have a method to create certain objects and store them with a key.
• It needs another method, which when passed with a key as a parameter, returns the object in question.
• working
• Processing the incoming URL, so our “index.php” file can route the request correctly
• Building URLs based on a series of parameters, a query string, and the URLdisplay/generation method we use
• Pagination

Pattern Implementation: Registry�

• The code in the book makes up the basics of our registry, with two arrays:
• One for objects
• One for settings

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Pattern Implementation: Singleton�

• The singleton pattern is very easy to implement, as it requires only a few minor changes to a standard PHP class, to ensure that it is only ever instantiated once.
• Needs
• A private constructor is used to prevent the direct creation of objects from the class.
• The expensive process is performed within the private constructor.
• The only way to create an instance from the class is by using a static method that creates the object only if it wasn't already created.

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Routing requests