Questions tagged [object-oriented]

A methodology that enables a system to be modeled as a set of objects that can be controlled and manipulated in a modular manner

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81
votes
2answers
12k views

Are there any OO-principles that are practically applicable for Javascript?

Javascript is a prototype-based object oriented language but can become class-based in a variety of ways, either by: Writing the functions to be used as classes by yourself Use a nifty class system ...
182
votes
16answers
129k views

When are Getters and Setters Justified

Getters and setters are often criticized as being not proper OO. On the other hand most OO code I've seen has extensive getters and setters. When are getters and setters justified? Do you try to ...
44
votes
8answers
10k views

What is the real responsibility of a class?

I keep wondering if it is legitimate to use verbs that are based on nouns in OOP. I came across this brilliant article, though I still disagree with the point it makes. To explain the problem a bit ...
22
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4answers
10k views

Make methods that do not depend on instance fields, static?

Recently I started programming in Groovy for a integration testing framework, for a Java project. I use Intellij IDEA with Groovy plug-in and I am surprised to see as a warning for all the methods ...
148
votes
14answers
42k views

Where does this concept of “favor composition over inheritance” come from?

In the last few months, the mantra "favor composition over inheritance" seems to have sprung up out of nowhere and become almost some sort of meme within the programming community. And every time I ...
16
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4answers
2k views

Staying OO and Testable while working with a database

What are some OOP strategies for working with a database but keeping things unit testable? Say I have a User class and my production environment works against MySQL. I see a couple possible approaches,...
219
votes
15answers
204k views

Why do we need private variables?

Why do we need private variables in classes? Every book on programming I've read says this is a private variable, this is how you define it but stops there. The wording of these explanations always ...
34
votes
4answers
9k views

The principle of least knowledge

I understand the motive behind the principle of least knowledge, but I find some disadvantages if I try to apply it in my design. One of the examples of this principle (actually how not to use it), ...
57
votes
8answers
12k views

How do I prove or disprove “God objects” are wrong?

Problem Summary: Long story short, I inherited a code base and a development team I am not allowed to replace and the use of God Objects is a big issue. Going forward, I want to have us re-factor ...
49
votes
9answers
12k views

Explanation on how “Tell, Don't Ask” is considered good OO

This blogpost was posted on Hacker News with several upvotes. Coming from C++, most of these examples seem to go against what I've been taught. Such as example #2: Bad: def check_for_overheating(...
36
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6answers
30k views

Understanding “programming to an interface”

I have come across the term "programming to an interface instead of an implementation" a lot, and I think I kind of understand what it means. But I want to make sure I understand it's benefits and it'...
129
votes
14answers
85k views

What is the ideal length of a method for you? [closed]

In object-oriented programming, there is of course no exact rule on the maximum length of a method , but I still found these two quotes somewhat contradicting each other, so I would like to hear what ...
71
votes
14answers
6k views

Clarify the Single Responsibility Principle

The Single Responsibility Principle states that a class should do one and only one thing. Some cases are pretty clear cut. Others, though, are difficult because what looks like "one thing" when ...
66
votes
10answers
43k views

Can't I just use all static methods?

What's the difference between the two UpdateSubject methods below? I felt using static methods is better if you just want to operate on the entities. In which situations should I go with non-static ...
11
votes
6answers
3k views

What are the practical ways to implement the SRP?

Simply what are the practical techniques people use to check if a class violates the single responsibility principle? I know that a class should have only one reason to change, but that sentence is ...
107
votes
4answers
21k views

So what *did* Alan Kay really mean by the term “object-oriented”?

Reportedly, Alan Kay is the inventor of the term "object oriented". And he is often quoted as having said that what we call OO today is not what he meant. For example, I just found this on Google: ...
44
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3answers
32k views

Programming SOLID Principles

Over time I could understand two parts of SOLID – the “S” and “O”. “O” – I learned Open Closed Principle with the help of Inheritance and Strategy Pattern. “S” – I learned Single Responsibility ...
54
votes
9answers
17k views

Code Smell: Inheritance Abuse [duplicate]

It's been generally accepted in the OO community that one should "favor composition over inheritance". On the other hand, inheritance does provide both polymorphism and a straightforward, terse way of ...
20
votes
3answers
8k views

How does strengthening of preconditions and weakening of postconditions violate Liskov substitution principle?

I read that Liskov's substitution principle is violated if : Preconditions are strengthened, or Postconditions are weakened But I don't get fully yet how these two points would violate Liskov ...
256
votes
14answers
104k views

Should we avoid object creation in Java?

I was told by a colleague that in Java object creation is the most expensive operation you could perform. So I can only conclude to create as few objects as possible. This seems somewhat to defeat ...
80
votes
12answers
51k views

What's the benefit of object-oriented programming over procedural programming?

I'm trying to understand the difference between procedural languages like C and object-oriented languages like C++. I've never used C++, but I've been discussing with my friends on how to ...
96
votes
5answers
28k views

Functional Programming vs. OOP [closed]

I've heard a lot of talk about using functional languages such as Haskell as of late. What are some of the big differences, pros and cons of functional programming vs. object-oriented programming?
17
votes
6answers
4k views

Method chaining vs encapsulation

There is the classic OOP problem of method chaining vs "single-access-point" methods: main.getA().getB().getC().transmogrify(x, y) vs main.getA().transmogrifyMyC(x, y) The first seems to have the ...
13
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1answer
3k views

Is wrapping a third party code the only solution to unit test its consumers?

I'm doing unit testing and in one of my classes I need to send a mail from one of the methods, so using constructor injection I inject an instance of Zend_Mail class which is in Zend framework. Now ...
18
votes
3answers
2k views

Is there a specific name for the “Square inherits from Rectangle” paradox?

A certain failure of OOP is shown with a class Square inheriting from Rectangle, where logically Square is a specialization of Rectangle and should therefore inherit from it, but everything falls ...
250
votes
23answers
198k views

If immutable objects are good, why do people keep creating mutable objects? [closed]

If immutable objects¹ are good, simple and offer benefits in concurrent programming why do programmers keep creating mutable objects²? I have four years of experience in Java programming and as I see ...
127
votes
6answers
67k views

What really is the “business logic”?

I'm working with web development since 2009, when I started with PHP. When I moved to ASP.NET I've heard a lot about DDD and OOAD where a lot of focus is given to this "business logic" and "business ...
34
votes
3answers
58k views

When to use a Singleton and when to use a static class [duplicate]

I've searched about this here and on StackOverflow and found some differences between the two. But I'm still not sure in what cases one would prefer a Singleton, and in what cases one would choose to ...
35
votes
4answers
10k views

What is the principle of least astonishment?

In programming what is called Principle of Least Astonishment? How is this concept related to designing good APIs? Is this something applicable to only object oriented programming or does it permeate ...
54
votes
9answers
39k views

Should the methods of a class call its own getters and setters?

Where I work I see lots of classes that do things like this: public class ClassThatCallsItsOwnGettersAndSetters { private String field; public String getField() { return field; }...
45
votes
11answers
8k views

Are error variables an anti-pattern or good design?

In order to handle several possible errors that shouldn't halt execution, I have an error variable that clients can check and use to throw exceptions. Is this an Anti-Pattern? Is there a better way to ...
9
votes
6answers
1k views

Significant amount of the time, I can't think of a reason to have an object instead of a static class. Do objects have more benefits than I think? [closed]

I understand the concept of an object, and as a Java programmer I feel the OO paradigm comes rather naturally to me in practice. However recently I found myself thinking: Wait a second, what are ...
95
votes
15answers
50k views

What makes C so popular in the age of OOP? [closed]

I code a lot in both C and C++, but did not expect C to be the second most popular language, slightly behind Java. TIOBE Programming Community Index I'm curious as to why, in this age of OOP, C is ...
59
votes
8answers
24k views

Is ORM an Anti-Pattern? [closed]

I had a very stimulating and interessting discussion with a colleague about ORM and its pros and cons. In my opinion, an ORM is useful only in the rarest cases. At least in my experience. But I don't ...
78
votes
4answers
21k views

Why do many software developers violate the open/closed principle?

Why do many software developers violate the open/closed principle by modifying many things like renaming functions which will break the application after upgrading? This question jumps to my head ...
28
votes
9answers
8k views

What can go wrong if the Liskov substitution principle is violated?

I was following this highly voted question on possible violation of Liskov Substitution principle. I know what the Liskov Substitution principle is, but what is still not clear in my mind is what ...
49
votes
3answers
58k views

Which is a better practice - helper methods as instance or static?

This question is subjective but I was just curious how most programmers approach this. The sample below is in pseudo-C# but this should apply to Java, C++, and other OOP languages as well. Anyway, ...
12
votes
6answers
12k views

Are Get-Set methods a violation of Encapsulation? [duplicate]

Possible Duplicate: When are Getters and Setters Justified In an Object oriented framework, one believes there must be strict encapsulation. Hence, internal variables are not to be exposed to ...
7
votes
4answers
5k views

When or why should one use getters/setters for class properties instead of simply making them public properties?

I program primarily in ColdFusion but this is a general OOP question. Is there any benefit to using: getProp() { return prop; } setProp(val) { prop = val; } As opposed to simply obj = ...
21
votes
4answers
3k views

“Too object-oriented”

I come from a strong OO background, and I have recently started working in an organization which, although the code is written in Java, has a lot less emphasis on good OO design than what I am used to....
229
votes
9answers
236k views

Aggregation vs Composition

I understand what composition is in OOP, but I am not able to get a clear idea of what Aggregation is. Can someone explain?
108
votes
13answers
26k views

Should I avoid private methods if I perform TDD?

I'm just now learning TDD. It's my understanding that private methods are untestable and shouldn't be worried about because the public API will provide enough information for verifying an object's ...
44
votes
10answers
100k views

Why use an interface when the class can directly implement the functions? [duplicate]

Possible Duplicate: Why are interfaces useful? Like most faculty, my java faculty introduced interface without explaining or even mentioning its practical use. Now I imagine interfaces have a ...
76
votes
8answers
92k views

Why have private static methods?

I just wanted to clear up a question I have. What is the point of having a private static method as opposed to a normal method with private visibility? I would have thought an advantage to having a ...
35
votes
11answers
20k views

Advantages of object-oriented programming [closed]

Note: this question is an edited excerpt from a blog posting I wrote a few months ago. After placing a link to the blog in a comment on Programmers.SE someone requested that I post a question here so ...
53
votes
20answers
20k views

Does Object Oriented Programming Really Model The Real World? [closed]

I've seen it commonly repeated the object-oriented programming is based on modeling the real world but is it? It seems to me that is not true of anything outside of the business layer. My GUI classes/...
40
votes
3answers
55k views

What is message passing in OO?

I've been studying OO programming, primarily in C++, C# and Java. I thought I had a good grasp on it with my understanding of encapsulation, inheritance and polymorphism. One frequently referenced ...
46
votes
7answers
9k views

Complete immutability and Object Oriented Programming

In most OOP languages, objects are generally mutable with a limited set of exceptions (like e.g. tuples and strings in python). In most functional languages, data is immutable. Both mutable and ...
12
votes
4answers
2k views

How much design to do first? [duplicate]

I have never worked with a professional software development team. As such, analyzing and thinking about each and every aspect of my software does not come naturally to me. Whenever I strike an idea ...
28
votes
4answers
6k views

Clarify the Open/Closed Principle

As I have had it explained, the open/closed principle states that once written code should not be modified (aside from bug fixes). But if my business rules change shouldn't I modify the code ...

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