Book Image

Agile Technical Practices Distilled

By : Pedro M. Santos, Marco Consolaro, Alessandro Di Gioia
Book Image

Agile Technical Practices Distilled

By: Pedro M. Santos, Marco Consolaro, Alessandro Di Gioia

Overview of this book

The number of popular technical practices has grown exponentially in the last few years. Learning the common fundamental software development practices can help you become a better programmer. This book uses the term Agile as a wide umbrella and covers Agile principles and practices, as well as most methodologies associated with it. You’ll begin by discovering how driver-navigator, chess clock, and other techniques used in the pair programming approach introduce discipline while writing code. You’ll then learn to safely change the design of your code using refactoring. While learning these techniques, you’ll also explore various best practices to write efficient tests. The concluding chapters of the book delve deep into the SOLID principles - the five design principles that you can use to make your software more understandable, flexible and maintainable. By the end of the book, you will have discovered new ideas for improving your software design skills, the relationship within your team, and the way your business works.
Table of Contents (31 chapters)
Free Chapter
1
Section 1
7
Section 2
13
Section 3
19
Section 4
25
Chapter 21
28
License: CyberDojo

Liskov Substitution Principle

"A type hierarchy is composed of subtypes and super types. The intuitive idea of a subtype is one whose objects provide all the behavior of objects of another type (the super type) plus something extra. What is wanted here is something like the following substitution property: If for each object o1 of type S there is an object o2 of type T such that for all programs P defined in terms of T, the behavior of P is unchanged when o1 is substituted for o2, then S is a subtype of T."

Barbara Liskov, Data Abstraction and Hierarchy

If you don't understand this, don't worry. Neither do we! Instead, let's look at it from a less academic, mere mortal point of view.

In simple terms, the Liskov Substitution Principle (LSP) says that derived classes should keep promises made by base classes. This also applies to interfaces, and it means that classes that implement some interface should keep the promises made by that interface...