About Cohesion

Cohesion is a measure of the degree to which the elements of a module belong together. Yourdon & Constantine in Structured Design, 1979 In essence, cohesion is a measure of ensuring that one element (one class) has a single responsibility. Measuring cohesion is tricky (as pretty much everything else in SE). The metrics tend to...

Introduction

I've been attending a course on setting up a business. Maybe one day I'll do it, but for now maybe some of the material will be useful to somebody else. Throughout this 'course' there are several themes that you will develop: Achievement: be clear about your outcomes Team: is the most important asset - these...

Intro into Software Complexity

No Silver Bullet — Essence and Accidents of Software Engineering Fred Brooks This is one of the famous quotes by Turing Award wining Fred Brooks. Complexity of software is tough to define. It is a measure of your program which is partially about size and partially about understandability (clarity) of the code. Complex code does...

Singleton

Singleton is also a very popular design pattern, although when not used appropriately it does become an anti- pattern. It is used when we need an object to be unique and easily accessible from all parts of the application e.g. database handler or loggers are frequently used. It is often considered an anti-pattern because is...

Callback

Callback design pattern allows us to avoid "freezing" the rest of the application if a method takes too long to return. It is very useful if running computationally-expensive or time unpredictable methods. It does generally involve running in a separate thread/task. The solution involves creating IXCallback interface which contains method called whn the slow operation...

Factory

Factory is one of the most popular design pattern out there. It is used to simply creation of the objects of different classes that inherit from a common super-class (or interface X) depending on some condition. The Recipe In order to create a factory for a class X: Create an XFactory class Add an X...

Command Stack

Command stack is a design patter if we need to support for undo/redo operations. There are two aspects to this design pattern ICommand interface where we can define the behaviour of the execution and undo operation and a CommandStack which is a generic. Create an ICommand interface with methods execute() and undo() All undoable/redoable actions...