 What is SOLID  The S in SOLID  The O in SOLID  The L in SOLID  The I in SOLID  The D in SOLID  Questions

 A means to avoid technical debt  Decrease Coupling  Increase Cohesion  Maintainable  Extensible  Testable

 Guidelines, NOT LAWS You got to know when to hold’em, know when to fold’em, Know when to walk away and know when to run. -Kenny Rogers

Application Flat File Sender Send GetMessage

Single Responsibility Principle There should never be more than one reason for a class to change -Uncle Bob

VIOLATES THE PRINCIPLEABIDES BY THE PRINCIPLE Application Flat File Sender Send GetMessage Application Flat File FileReader GetMessage Sender Send

Application Flat File FileReader GetMessage Sender Send XML File

Open-Close Principle Software entities (classes, modules, functions, etc…) should be open for extension, but closed for modification -Uncle Bob

VIOLATES THE PRINCIPLEABIDES BY THE PRINCIPLE Application Flat File FileReader GetMessage Sender Send XML File Application Flat File BaseFileTypeReader CanRead ReadFile Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader

Application Flat File BaseFileTypeReader CanRead ReadFile Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader DB File DbFileReader CanRead ReadFile Database

Liskov Substitution Principle Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it -Uncle Bob

VIOLATES THE PRINCIPLEABIDES BY THE PRINCIPLE Application Flat File BaseFileTypeReader CanRead ReadFile Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader DB File DbFileReader CanRead ReadFile Database Application Flat File BaseFileTypeReader CanRead ReadFile Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader DbReader GetMessage Database

Application Flat File BaseFileTypeReader CanRead ReadFile Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader Database IReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader DbReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader

Interface Segregation Principle Clients should not be forced to depend upon interfaces that they do not use -Uncle Bob

ABIDES BY THE PRINCIPLE Application Flat File BaseFileTypeReader CanRead ReadFile Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader Database IReader GetMessage DbReader GetMessage IFileTypeReaderRegisterable RegisterDefaultFileTypeReader RegisterFileTypeReader

Dependency Inversion Principle High level modules should not depend upon low level modules. Both should depend upon abstractions Abstractions should not depend upon details. Details should depend upon abstractions -Uncle Bob

ABIDES BY THE PRINCIPLE Application Flat File BaseFileTypeReader CanRead ReadFile I Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader Database IReader GetMessage DbReader GetMessage IFileTypeReaderRegisterable RegisterDefaultFileTypeReader RegisterFileTypeReader Sender Send

Application Flat File Sender Send GetMessage Xml File Database

Application Flat File BaseFileTypeReader CanRead ReadFile I Sender Send XML File FlatFileReader CanRead ReadFile XmlFileReader CanRead ReadFile FileReader GetMessage RegisterDefaultFileTypeReader RegisterFileTypeReader Database IReader GetMessage DbReader GetMessage IFileTypeReaderRegisterable RegisterDefaultFileTypeReader RegisterFileTypeReader Sender Send

 Martin Folwer – Technical Debt   Wikipedia – Coupling   Wikipedia – Cohesion   Robert Martin – The Principles of OOD   Derick Bailey – SOLID Principles – Step by step code  training/tree/master/SOLID%20Principles%20- %20Step%20By%20Step%20Code training/tree/master/SOLID%20Principles%20- %20Step%20By%20Step%20Code

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