repository Design Pattern
Vo Xuan Tien
High Level Application Design
Good design?
Object creation, persistence, delivery are outside of the core
Good Design
Dependencies point only toward the business logic.
Benefits
- Swap the heavy MySQL database with a lightweight SQLite3 database.
- Drop your current MVC framework and replacing it with another, without touching the business logic.
- Delivering the results of your application through a third party API and not over HTTP.
- Making all these changes and your tests would still pass.
repository
What?
Connect business logic, factories and persistence.
Repository
When?
Any application has to work with persistence and with some kind of list of items.
Factory
What?
It’s a class that acts as a factory of object instances.
Factory
What?
It will know how to take all the information needed to build an object.
Factory
What?
$buttons = array('image', 'input', 'flash');
foreach($buttons as $b) {
echo ButtonFactory::createButton($b)->getHtml();
}
Gateways
What?
Offers the connection between the business logic and the database itself.
Gateways
What?
Do the queries on the database and get raw data.
Gateways
What?
Raw data must then be passed to the Factories.
Problems
Duplication by Data Handling
Problems
Duplication by Data Retrieval Logic
Problems
Duplication by Data Persistence Logic
Repository for Data Retrieval
Repository for Data Persistence
Practice
- Blog application
- Comments and Posts
- Comments belong to Posts
- Persist comments and posts
-
Retrieve comments and posts