Questions tagged [class-design]

General guidelines on how to design classes with best known industry practices.

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192
votes
16answers
17k views

When using the Single Responsibility Principle, what constitutes a “responsibility?”

It seems pretty clear that "Single Responsibility Principle" does not mean "only does one thing." That's what methods are for. public Interface CustomerCRUD { public void Create(Customer ...
21
votes
5answers
2k views

How can you decompose a constructor?

Lets say I have a Enemy class, and the constructor would look something like: public Enemy(String name, float width, float height, Vector2 position, float speed, int maxHp, int ...
16
votes
7answers
6k views

At what point do immutable classes become a burden?

When designing classes to hold your data model I've read it can be useful to create immutable objects but at what point does the burden of constructor parameter lists and deep copies become too much ...
39
votes
6answers
15k views

Prefer class members or passing arguments between internal methods?

Suppose within the private portion of a class there is a value which is utilized by multiple private methods. Do people prefer having this defined as a member variable for the class or passing it as ...
0
votes
3answers
823 views

How do you balance out code structuring (few big functions vs. many small ones)?

The golden rule of code structuring is always said as splitting into many sub functions is a good thing. Though I noticed it becomes a problem in complex applications when a class of e.g. 10 bigger ...
21
votes
4answers
20k views

C++ - Constructor or Initialize Method to Startup [duplicate]

Possible Duplicate: Avoid having an initialization method I want to determine when to do non-trivial initialization of a class. I see two times to do initialization: constructor and other method. ...
17
votes
4answers
14k views

Why define a Java object using interface (e.g. Map) rather than implementation (HashMap)

In most Java code, I see people declare Java objects like this: Map<String, String> hashMap = new HashMap<>(); List<String> list = new ArrayList<>(); instead of: HashMap<...
10
votes
5answers
9k views

Interface and Inheritance: Best of both worlds?

I 'discovered' interfaces and I started to love them. The beauty of an interface is that it is a contract, and any object that fulfills that contract can be used wherever that interface is required. ...
122
votes
9answers
25k views

Is there any “real” reason multiple inheritance is hated?

I've always liked the idea of having multiple inheritance supported in a language. Most often though it's intentionally forgone, and the supposed "replacement" is interfaces. Interfaces simply do ...
11
votes
4answers
12k views

Use Dependency Injection For Data Objects?

I'm just learning about dependency injection, and am stuck on something. Dependency Injection recommends sending dependent classes through the constructor, but I'm wondering if this is necessary for ...
12
votes
2answers
2k views

Should I expose a “computed” value as a property or a method?

I have a C# class that represents a content type in a web content management system. We have a field that allows a web content editor to enter an HTML template for how the object is displayed. It ...
3
votes
4answers
7k views

c++ coding practice class vs. “free” functions

I am currently writing my first bigger project in c++. Its basic linear algebra. I am aware that boost libraries and others exist, but for various reasons I need to write my own. Purpose of the ...
23
votes
2answers
4k views

Is it a good idea to provide different function signatures that do the same thing?

Here is a C++ class that gets constructed with three values. class Foo{ //Constructor Foo(std::string, int, char); private: std::string foo; char bar; int baz; }; All of the ...
1
vote
1answer
388 views

When should I pass value as class variable and when as a method argument?

Is there a general rule of thumb, when we should pass a value as as class variable and when as a method argument? Or is it just a choice of the developer? For example -- are there any reasons, why ...
1
vote
4answers
4k views

Force Derived Class to Implement Static Method C#

So the situation is like, I have few classes, all of which have a standard CRUD methods but static. I want to create a base class which will be inherited so that it can force to implement this CRUD ...
0
votes
2answers
2k views

A sample Memento pattern: Is it correct?

Following this query on memento pattern, I have tried to put my understanding to test. Memento pattern stands for three things: Saving state of the "memento" object for its successful ...
48
votes
6answers
6k views

What would be the disadvantage to defining a class as a subclass of a list of itself?

In a recent project of mine, I defined a class with the following header: public class Node extends ArrayList<Node> { ... } However, after discussing with my CS professor, he stated that ...
60
votes
12answers
8k views

Is it bad practice to pass instances through several layers?

In my program design, I often come to the point where I have to pass object instances through several classes. For example, if I have a controller that loads an audio file, and then passes it to a ...
24
votes
5answers
26k views

When and why to use Nested Classes?

Using Object Oriented Programming we have the power to create a class inside a class (a nested class), but I have never created a nested class in my 4 years of coding experience. What are nested ...
14
votes
2answers
1k views

Design: Object method vs separate class's method which takes Object as parameter?

For example, is it better to do: Pdf pdf = new Pdf(); pdf.Print(); or: Pdf pdf = new Pdf(); PdfPrinter printer = new PdfPrinter(); printer.Print(pdf); Another example: Country m = new Country("...
11
votes
3answers
5k views

How should an `Employee` class be designed?

I am trying to create a program for managing employees. I cannot, however, figure out how to design the Employee class. My goal is to be able to create and manipulate employee data on the database ...
15
votes
4answers
6k views

Is It “Wrong”/Bad Design To Put A Thread/Background Worker In A Class?

I have a class that will read from Excel (C# and .Net 4) and in that class I have a background worker that will load the data from Excel while the UI can remain responsive. My question is as follows: ...
11
votes
2answers
16k views

Thoughts and Best Practices on Static Classes and Members [closed]

I am very curious as to thoughts and industry best practices regarding static members, or entire static classes. Are there any downsides to this, or does it participate in any anti-patterns? I see ...
9
votes
5answers
1k views

How do we know to favour composition over generalisation is always the right choice?

Whether an object physically exists or not, we can choose to model it in different ways. We could arbitarily use generalisation or composition in many cases. However, the GoF principle of "favour ...
8
votes
4answers
3k views

Method flags as arguments or as member variables?

I think the title "Method flags as arguments or as member variables?" may be suboptimal, but as I'm missing any better terminology atm., here goes: I'm currently trying to get my head around the ...
10
votes
5answers
4k views

How to resolve class interdependence in my C++ code?

In my C++ project, I have two classes, Particle and Contact. In the Particle class, I have a member variable std::vector<Contact> contacts which contains all contacts of a Particle object, and ...
0
votes
1answer
1k views

When should a class be final? [duplicate]

I've only really seen this on Java's wrapper classes (String, Integer, etc.), but never in open-source projects, and I was never taught about it in any books or classes. I know it means the class can'...
12
votes
4answers
3k views

Object Oriented Programming: getters/setters or logical names

I'm currently thinking about an interface to a class I'm writing. This class contains styles for a character, for example whether the character is bold, italic, underlined, etc. I've been debating ...
7
votes
3answers
855 views

OOP Practice: how to best handle dependent dependencies

I have a problem with the design shown in the picture. My Section class has some TextBlocks (or simply Blocks). The section should be drawn on a page (a Bitmap as device context). It sets the blocks ...
13
votes
9answers
3k views

Isn't class scope purely for organization? [duplicate]

Isn't scope just a way to organize classes, preventing outside code from accessing certain things you don't want accessed? More specifically, is there any functional gain to having public, protected, ...
5
votes
2answers
5k views

Design patterns for creating objects that have a list of objects that also have a list of objects

In terms of good OOP design, what is the best way to structure code that is just containers of list of objects that contains other lists of objects that also are just other containers? Example: A ...
5
votes
4answers
2k views

Should I put UI and logic in separate classes?

I currently work on a hobby project which I use to learn more about Android/Java programming and programming in general. Recently, I decided to integrate jUnit into the project. Just getting it in ...
4
votes
2answers
174 views

Designing my classes with relationships

I need to build a UI for entering values to the database. I am stuck with my class design to achieve it. I need a UI where I am able to enter the name of the system. Each system can have many options....
1
vote
2answers
218 views

Object oriented Classes and single responsibility [duplicate]

I'm reading a book that explain that it is a good thing that classes have a single responsibility, that is, that they do a single thing. I can understand how to implement this in some cases I ...
3
votes
2answers
1k views

One boilerplate class or many similar classes?

Lets say I'm trying to model a variety of objects that are virtually identical, the only difference being their class variables. Am I better off creating one boilerplate class and just calling the ...
2
votes
6answers
4k views

Class Design — Multiple Calls from One Method or One Call from Multiple Methods?

I've been working on some code recently that interfaces with a CMS we use and it's presented me with a question on class design that I think is applicable in a number of situations. Essentially, what ...
1
vote
2answers
293 views

Dependencies between class attributes

I wonder whether there is a concept for attribute dependency in object oriented terminology? It's an example showing what I mean with attribute dependency: 2DShapeclass may have an areaattribute. ...
0
votes
2answers
3k views

How To Invoke A Method When It's Class is Accessed (Any Method) - “OnClassEnter”

I am working on a C# net micro framework project, in particular an I2C bus management/class. I have several different I2C devices each defined in separate classes which contain all of the devices' ...