Articles by Francois Buys

The I in SOLID

Today we will discuss the I in SOLID which, you may or may not know, represents the Interface Segregation Principle (ISP). This is the fourth article in the SOLID series. We have already discussed the Single Responsibility, Open/Closed and Liskov Substitution principles.

In this post we will discuss the value of and the process for crafting easy to maintain interfaces. If we have enough time we will also discuss how interfaces might apply to dynamically typed languages such as Ruby. With no further ado, let us start by finding out what an interface actually is.

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The L in SOLID

This post is the third one in the SOLID principles series. The first post discussed the single responsibility principle and in the second post we discussed the open / closed principle. Next, as the title suggests, we will take a look at the principle represented by the letter L from the SOLID acronym. L is for the Liskov Substitution Principle (LSP).

In simple terms LSP requires that supertypes and subtypes be swappable without affecting the correctness of a program.

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The O in Solid

In a previous post we considered the practical value of the Single Responsibility Principle (SRP). This is the second post in this series where we take a deeper look at each of the SOLID principles.

Robert C. Martin (a.k.a. “uncle Bob”) refers to the O in Solid as the heart of Object Oriented (OO) design. He goes so far as to say that this principle improves reusability and maintainability more than any other OO principle. You most likely already know that the O in SOLID belongs to the Open/Closed Principle (OCP).

We often hear about SRP or DRY (don’t repeat yourself) but seemingly less often about OCP. It turns out that this principle lays the foundation for many of the OO best practices. In this post we will talk about OCP and find out why uncle Bob is such an advocate of OCP.

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