Fundamentally, the Liskov Substitution Principle (LSP) is concerned with well-behaved sub-types. What does it mean for subtypes to be well-behaved or, more specifically, substitutable? What even is a subtype? Subtypes A child class is a subtype, and an interface implementation is also a subtype. For example, a supertype Animal is a…

It's time to up the ante and challenge ChatGPT's code-generating abilities. Last time, I requested OpenAI's Large Language Model (LLM) AI to write a ShoppingCart class. ChatGPT delivered and produced surprisingly clean, working code. Well done, ChatGPT! Yet, how will ChatGPT fare with something a bit grittier and more complicated…

Imagine we have a system for managing users. Within the system source code, two separate arrays hold information on users. One contains unique identifiers for users, represented by integer user ids: [1, 7, 9, 4, 12] The second array contains the names of the users: ["Dave", "Carol", "Alice", "Eddie", "Bruce"] …

If you’ve been programming for a few years, you likely will have come across a Genius Programmer or two. You may be sitting next to one right now. Genius programmers are easy to spot — they’re the ones who know even obscure programming frameworks in intimate detail. They love exploring…

These days, it seems, every developer is test-driving — and then writing about — the code-generating capabilities of OpenAI’s ChatGPT. Admittedly, I also was curious about the quality of code ChatGPT could generate. …

Three rules govern Test-Driven Development (TDD). The first rule asserts, ‘Only write production code to make a failing unit test pass. ‘. Here we have the central tenet of TDD — that we hold off writing behavioural code we have a unit test demanding the behaviour. And this test must…

Business Logic Business Logic is the beating heart of every software system. Yet, many software developers need help identifying it. If we collectively want to build (and maintain!) programs that are easy to work with, we need to get good at this one task. …

Command and Queries Functions comprise the two complementary behaviours of Command Query Responsibility Separation or CQRS. While Query functions measure and report on the state of a system, Command functions, or Commands for short, change a system’s state. Command Functions How do Command Functions alter the state of a system? Simple, they…

When I first started programming, I fell in love — with the switch statement. Here I had found a way to construct long if ... elseif ... elseif ... else conditionals in a slightly more concise way. I was in programming heaven. The switch statement The switch statement exists in many programming languages…