Firstly, what is the Dependency Inversion Principle?Definition: One should depend upon abstractions and not concrete instances. Typically in a software application, high level components need to depend on lower level components. If the low level components are ‘hard-coded’ into the high level components this causes two problems. 1. Testability The first problem is testability. It …
What is the Interface Segregation Principle? Definition: Many client-specific interfaces are better than one general-purpose interface. This principle is fairly straightforward. It is really just saying to keep your interfaces to a specific role, keep them small and concise. Reason: This enables code concrete classes not to have to implement every single method regardless of …
Firstly, what is the Liskov substitution principle? Definition: Objects in an application should be replaceable with instances of their subtypes without altering the correctness of that program. To understand the Liskov substitution principle is useful to understand the concepts of Contravariance and Covariance. Contravariance Contravariance is the conversion of a class from its sub class …
What is the Open / Closed Principle? Definition: An object should be open for extension but closed for modification. This principle states that code should only be modified to fix bugs and errors and to extend the functionality a new class should be used. Typically the new class would be a derived class to enable …
Firstly, what is the Single Responsibility Principle? Definition: An object should have a single responsibility. In practice, to adhere to this principle, an object is a class and that class’s functionality is grouped around a single idea or unit of responsibility. Robert C Martin defined responsibility as a reason to change. This means that a …
What are The SOLID principles of Object Orientated design? Well, the 5 basic principles of OO design were put together in the early 2000s by Michael Feathers and Robert C Martin. They are intended to allow the developer to create software that is easy to maintain and extend over time. The patterns which have come …
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Over the years I have found a commonality in the way developers think, which is fundamentally different than non-technical managers. This difference has often perplexed me and I have often wondered exactly what the nature of this difference is. It usually manifests itself in the form of developers thinking they are in some way better …
