This note will list few things you should try to avoid in your design. Please also see notes on SOLID Principles and summary of additional design principles and best practices.

1. Run-Time Type Identification (RTTI)

   • Design that require you to check for the actual type of the reference object should be avoided (e.g. if(type(something) = something, do something). 

2. Cyclomatic complexity (CC)

SOLID is a mnemonic acronym introduced by Michael Feathers for five of the principles named by Robert C. Martin, and when applied together, these intend to make it more likely that a programmer will create a system that is easy to maintain and extend over time.

1. (++) Single responsibility principle (SRP)

   • ​Every class should have a single responsibility, and that responsibility should be entirely encapsulated by the class. All its services should be narrowly aligned with that responsibility. 

Object Oriented Design principles are very important and are sometimes considered even more important than design patterns. All design patterns are based on one or more of the design principles. Having thorough understanding of the design principles will help you understand the design paterns better and faster, and will even help you solve many design scenarios if you can't find a design pattern fitting that scenario.