Design Patterns

Introduction to Design Patterns given in 2012 for AC Partners and in 2019 for itenium.

Some material:

• JavaScript exercise info
• Design Pattern definitions for this technical session
• All design patterns with UML diagrams

JavaScript

Creating a framework for generating user forms:

npm install

# React
cd JavaScript/impl-react
npm start

# Angular
cd JavaScript/impl-angular
npm start

JavaScript

See Handout.md

Exercise SOLID

Angular - Bootstrap - FormWrapperDirective:

This high level component wraps a form control for use in a Bootstrap form
There are several problems:

• It has intimate knowledge of the low level controls (setting a specific extra class 'form-check' for 'toggle')
• Another big switch statement is waiting to happen here: A control can also appear in a navbar, ... with different classes

DotNet

1 OpenClosedPrinciple

Example 1-3: Calculating shape area

Adhering to the OpenClosedPrinciple by introducing a PureFabrication (IAreaCalculator) and using Polymorphism instead of type checking.

• Example 1: Calculate area of Circles
• Example 2: A naive implementation when Rectangles are added
• Example 3: Introducing the IAreaCalculator abstraction

Example 4-7: Saving files

Keeping the code DRY:

• Example 4: Code duplication for the different "file saving mechanisms"
• Example 5: A solution with TemplateMethod
• Example 7: A solution with Strategy
• Example 6: Use FactoryMethod on Example 5 to allow each "file saving mechanism" to return custom metadata

2 Patterns

• 1-2.Observer: Examples of Observer: builtin support with event EventHandler<EventArgs>
• 3.Decorator: Example with Streams

TODO: De CheatSheet zouden moeten genummerd zijn