OOP and the scope of a class, am I wrong?

[honey the codewitch]

You're probably safe. I ran into this while helping a student from South Africa

Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

[Ravi Bhavnani]

honey the codewitch wrote:

professors are teaching that classes are effectively a single action like ReadTextFile

I hope what they meant (but probably didn't clearly convey) is a recommendation for a TextFileReader class (that derives from FileReader that derives from StreamReader) that has methods like Read() and ReadToEnd(). /ravi

My new year resolution: 2048 x 1536 Home | Articles | My .NET bits | Freeware ravib(at)ravib(dot)com

[honey the codewitch]

Not at all. It had ParsePatientData, and OuputPatientData Yeah. It's like that. And the assignment required the name.

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[Mark Quennell]

I guess that could be considered a class in a command-based architecture, where ReadTextFile inherits from (or implements) some sort of base Command class and it contains all the information the processing system needs to perform that action, but it's a stretch, and certainly not to be taught as "the norm"...

[DT Bullock]

That's almost certainly what is being taught. It comes from the (very helpful) book 'Design Patterns' by Erich, Gamma, et. al. (aka. 'the Gang of Four' ... abbreviated everywhere to 'GoF'). It is useful in particular situations, and it has trade-offs. Professors should teach it, but I doubt they are advocating that it should be always done that way ... that's more likely students not grasping the nuance of when to apply the pattern.

[JeffL45]

Many people consider this a must read for OOP/class deisgn -

[Gary Wheeler]

honey the codewitch wrote:

In my mind, a class is a noun, not a verb, essentially

For me, a class may be either a noun or a verb. As a noun, the concept represented by the class is a thing, and the class provides information and operations for that thing. For a verb the concept is a process, and the class supports that process. I guess 'process' can be thought of as a noun, but thinking of it that way adds indirection to my thinking.

Software Zen: delete this;

[MikeCO10]

No, you are correct. Your car is a valid class as you define it. ReadTextFile() is a function. To be a valid class, imo, it would be TextFile as the class, with properties and actions. TextFile.length, etc. and TextFile.Read,write,etc. My take, in English grammar, is that a class should be a noun, with adjectives, verbs and possibly adverbs that go with it. If it's short of that, it deserves another look for consideration as a function or structure. I suppose, depending on the language, a class could be looked at as a convenient way to store a reusable. What a declaration nightmare that creates, using your example.

[BryanFazekas]

honey the codewitch wrote:

But I'm hearing that professors are teaching that classes are effectively a single action like ReadTextFile and it makes me a lot more irritated than I probably should be.

You're right. A class encapsulate a physical or logical object, including ways to interact with the object. What that professor is teaching is sheer idiocy. Many moons ago a friend relayed a story -- we worked for a consulting firm and he did the tech interview for a professor that had taught VB at the local community college for 5 years. She failed the interview and he recommended against hiring her. Why? She knew the syntax of the language better than he did, but she had NO idea how to actually program. She could answer questions such as "which method to use to add an item to a listbox" (something we didn't bother asking), but didn't know which construct to use for looping. She could write an if loop, but couldn't tell when to use if or while or foreach. He went into the interview assuming it was a formality, and ended up vetoing her. Far too many college professors have no real world experience.

[MarkTJohnson]

But he explained OOP that way and the implmentation in C++ was that way as well.

I’ve given up trying to be calm. However, I am open to feeling slightly less agitated. I’m begging you for the benefit of everyone, don’t be STUPID.

[Daniel Anderson 2021]

I`d say no you are not wrong, but the teacher is not necessarily wrong either. A class can be almost anything in C++. - Can be an interface - Can be a functor - Can be just data - Whatever... so, depending on how the teacher wants the thing to evolve he might direct his students. with very little or no context it is hard to decide who's right. If you are using class to model things, they can be names. If they model actions, they can be verbs. If they model attributes, they can be adjectives. classes are one of the mechanisms for encapsulation & data hiding after that, when I do code review, I usually check the coupling between the class and the client, this usually tells me if the data hiding or encapsulation is at a proper level or done right.

[DougInNC2]

0x01AA wrote:

Abstracting the reality is usually very hard.

Abstracting reality may be difficult but its absolutely essential. If you see a chair that you've never seen before and you don't have an abstract concept of what a chair is, how would you ever know its a chair? It sounds like this professor had a difficult time with the abstract concept of a class. It can be a difficult concept but I would think it would be a prerequisite to being an IT professor. But what do I know? I'm self taught and assume there a plenty of abstract concepts I'm just not aware of.

[obermd]

I would say TextReader is the superclass of ReadTextFile. Text doesn't always come in files.

[jochance]

Sounds like someone misunderstood. Those will be some messed up students if they come out thinking classes are/should be SRP. Methods/functions sure, but... OOP tends to be highly overrated when you turn on the ultra pedant. Probably through here, I've read recent articles from others who spit on DRY and recognize that classic OOP has some serious faults.

[Member_5893260]

Well, at least we'll never be unemployed!

[Dave B 68]

Why does it have to be one or the other? One class could model a physical object like a car while another could model an operation such as a database transaction, file operation, or something more complex. At the end of the day it is about using the tools to minimize the cost of solving problems. And concepts like encapsulation and polymorphism frequently are the best tools for the job.

[klinkenbecker]

To a large extent the 'normalization' of classes is akin to the normalization of data records. The atomic characteristics of a class, that would drive application decomposition (and vice versa), can vary between applications. Thus a useful class decomposition in one instance can be a dogs breakfast in another. There is a similar problem when looking at communications protocols - doctrine dictates multiple layers but these can severely impede and bloat small systems. As humans show every moment, it is possible to communicate without layers (with varying degrees of success), particularly when context is available. For humans effective communication is possible even when the context is ambiguous. For myself, I have classes that do the equivalent of 'ReadTextFile' or 'ReadComPort' - these typically act as base class for different types of parser such that the data is transformed in some way into an easily digestible form for another part of the app. Whereas one may aspire to a 'universal' set of pattern classes, their utility will generally boil down to adaptation within specific application constraints.

[honey the codewitch]

The directive in the assignment, which I had a copy of said literally name the class ReadTextFile.

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[honey the codewitch]

That's a good point. I was trying to get to the essence of it and simplify, but obviously I missed the mark in terms of covering every eventuality.

Check out my IoT graphics library here: https://honeythecodewitch.com/gfx And my IoT UI/User Experience library here: https://honeythecodewitch.com/uix

[Steve Naidamast]

I always split my OOP classes into two parts; classes for actions, and structures\structs for data. I just find it easier that way. I also try to limit what each would hold in the attempt to keep my classes\structures small. In the end, OOP's big advantage is its organizational capabilities within an application. And that organization is primarily up to the developer, not a professor...

Steve Naidamast Sr. Software Engineer Black Falcon Software, Inc. blackfalconsoftware@outlook.com