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Importance of the Interface Segregation Principle

Explore the Interface Segregation Principle within the SOLID design framework, focusing on how to separate interfaces so classes only implement methods they actually use. This lesson uses C# examples involving text processing to show how segregating interfaces improves code clarity and flexibility while avoiding unnecessary method implementations.

We'll cover the following...

Example of the interface segregation principle

The following playground contains a console application that reads text from a file and converts it to HTML:

Note: Run the following code. The program will ask for the file to convert. Enter sample.txt as the name of the file. When the program stops execution, press any key to return to the terminal. Now, enter the cat sample.html command to see the content after conversion.

This is the first paragraph. It has *bold text*.

This is the second paragraph. It has **italic text**.

This is the third paragraph. It has ~~text with strike-through~~.
Initial project setup

We have a TextProcessor named base class on lines 6–23 in the code provided below that converts paragraphs in the input text into HTML paragraphs by applying relevant tags.

C++
using System.Text;
using System.Text.RegularExpressions;
namespace TextToHtmlConvertor;
public class TextProcessor
{
  public virtual string ConvertText(string inputText)
  {
    var paragraphs = Regex.Split(inputText, @"(\r\n?|\n)").Where(p => p.Any(char.IsLetterOrDigit));
    var sb = new StringBuilder();
    foreach (var paragraph in paragraphs)
    {
      if (paragraph.Length == 0)
      {
        continue;
      }
      sb.AppendLine($"<p>{paragraph}</p>");
    }
    sb.AppendLine("<br/>"); 
    return sb.ToString(); 
  }
}

We also have a MdTextProcessor named derived ...