A design pattern is a general reusable solution to a commonly occurring problem in software design.

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193
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17answers
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Why is Global State so Evil?

Before we start this, let me say I'm well aware of the concepts of Abstraction and Dependency Injection. I don't need my eyes opened here. Well, most of us say, (too) many times without really ...
69
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2answers
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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 ...
85
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4answers
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What is an Anti-Corruption layer, and how is it used?

I'm trying to figure out what the Anti-Corruption layer really means. I know that it's a way to transition/work around legacy code or bad APIs. What I don't understand is how it works and what makes ...
83
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10answers
10k views

Are design patterns really essential nowadays?

I was reading "Coders at Work" and have faced the fact that some of the professionals interviewed in the book are not so enthusiastic about design patterns. I think that there are 2 main reasons for ...
50
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5answers
5k views

When is Singleton appropriate? [closed]

Some hold that the Singleton Pattern is always an anti-pattern. What do you think?
21
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7answers
4k views

How to determine if a class meets the single responsibility principle?

The Single Responsibility Principle is based on the high cohesion principle. The difference between the two is that a highly cohesive classes features a set of responsibilities that are strongly ...
142
votes
10answers
109k views

What is MVC, really?

As a serious programmer, how do you answer the question What is MVC? In my mind, MVC is sort of a nebulous topic — and because of that, if your audience is a learner, then you're free to ...
13
votes
6answers
2k views

Should I extract specific functionality into a function and why?

I have a large method which does 3 tasks, each of them can be extracted into a separate function. If I'll make an additional functions for each of that tasks, will it make my code better or worse and ...
126
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15answers
41k views

Do I need to use an interface when only one class will ever implement it?

Isn't the whole point of an interface to for multiple classes to adhere to a set of rules and implementations?
390
votes
13answers
132k views

So Singletons are bad, then what?

There has been a lot of discussion lately about the problems with using (and overusing) Singletons. I've been one of those people earlier in my career too. I can see what the problem is now, and yet, ...
32
votes
1answer
11k views

What is the difference between the factory pattern and abstract factory?

Having finally begun seriously trying to learn some basic patterns (very late in the career, but that's a different story), I'm trying to get my head around the differences between the Factory Pattern ...
10
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2answers
3k views

Choosing the right Design Pattern

I've always recognized the importance of utilizing design patterns. I'm curious as to how other developers go about choosing the most appropriate one. Do you use a series of characteristics (like a ...
18
votes
5answers
12k views

What is the difference between all-static-methods and applying a singleton pattern? [duplicate]

I am making a database to store information about the users of my website (I am using stuts2 and hence Java EE technology). For the database I'll be making a DBManager. Should I apply singleton ...
131
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14answers
43k views

“Never do in code what you can get the SQL server to do well for you” - Is this a recipe for a bad design?

It's an idea I've heard repeated in a handful of places. Some more or less acknowledging that once trying to solve a problem purely in SQL exceeds a certain level of complexity you should indeed be ...
43
votes
6answers
33k views

How essential is it to make a service layer?

I started building an app in 3 layers (DAL, BL, UI) [it mainly handles CRM, some sales reports and inventory]. A colleague told me that I must move to service layer pattern, that developers came to ...
62
votes
10answers
6k views

Non-OOP Design Patterns? [closed]

I have only heard the term "design pattern" being used for object oriented code, and the GoF patterns include only OOP design patterns, but design patterns are elegant solutions for commonly occuring ...
28
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2answers
23k views

Separating data access in ASP.NET MVC

I want to make sure I'm following industry standards and best practices with my first real crack at MVC. In this case, it's ASP.NET MVC, using C#. I will be using Entity Framework 4.1 for my model, ...
44
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8answers
15k 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 ...
24
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10answers
8k views

To design pattern, or not to design pattern [duplicate]

Design patterns are good, but complex. Should we use them in small projects? Implementing design patterns needs more sophisticated developers, which in turn raises project costs. On the other hand, ...
14
votes
7answers
3k views

What if I will not use Software Design Patterns? [closed]

What kind of problems may I face, if I won't use Software Design Patterns? Can you tell me about the problems of approaching the design using standard object-oriented techniques?
24
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6answers
2k views

How do I prevent unknowningly duplicating code?

I work on a rather large code base. Hundreds of classes, tons of different files, lots of functionality, takes more than 15 minutes to pull down a fresh copy, etc. A big problem with such a large ...
17
votes
11answers
1k views

Why are we supposed to use short functions to sectionalize our code? [duplicate]

I've seen an increasing trend in the programming world saying that it is good practice to separate code blocks into their own functions. Obviously, if that code block is reusable, you should do that. ...
5
votes
2answers
631 views

What is a good design pattern for multi-mode software?

I will explain my question by way of example, but I'd love a general solution. I am writing a JavaScript application that needs to function differently depending on its run-time context. To handle ...
5
votes
1answer
351 views

Derive from a base class but not include a condition in the base class's method

The current code looks like this: public class Details { Public void Populate() { WriteChapterDetails(); } public void WriteChapterDetails() { if ( ...
58
votes
7answers
65k views

Why should I use an MVC pattern?

It seems everyone doing web applications nowadays wants to use MVC for everything. I find it hard to convince myself to use this pattern, however. I understand the general idea is to separate the ...
59
votes
9answers
25k views

Why should I use a factory class instead of direct object construction?

I have seen the history of several С# and Java class library projects on GitHub and CodePlex, and I see a trend of switching to factory classes as opposed to direct object instantiation. Why should I ...
36
votes
12answers
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Is this a decent use-case for goto in C?

I really hesitate to ask this, because I don't want to "solicit debate, arguments, polling, or extended discussion" but I'm new to C and want to gain more insight into common patterns used in the ...
10
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3answers
1k views

Recommend a design pattern/approach to exposing/tolerating/recovering from system errors, Exception handling (e.g.s in Java, C++, Perl, PHP)

Can you recommend a design pattern/approach to exposing/tolerating/recovering from system errors, Exception handling (Java, C++, Perl, PHP)? Some errors need to be reported. Some errors can be ...
40
votes
11answers
6k 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 ...
13
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2answers
3k views

Differences between Design by Contract and Defensive Programming

Could Designing by Contract (DbC) be a way to program defensively? Is one way of programming better in some cases than the other?
14
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3answers
4k views

What is the pattern name for using method chaining to build an object? [closed]

I frequently use a pattern where I using method chaining to setup an object, similar to a Builder or Prototype pattern, but not creating new objects with each method call, instead modifying the ...
5
votes
3answers
2k views

How to create a manager class without global variables nor singletons?

I would like to implement some kind of manager class in my application. It will be in charge of loading textures, processing them, distributing them etc... At first, I wanted to make a global ...
5
votes
1answer
171 views

How should I handle incompatible configurations with the Builder pattern?

This is motivated by this answer to a separate question. The builder pattern is used to simplify complex initialization, especially with optional initialization parameters). But I don't know how to ...
0
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3answers
189 views

Select design pattern - user stage

I'm struggling to point a finger into the right design pattern. I have a web site which user can register and interact with the system. I want to add the following abilities to a user: Each user ...
72
votes
5answers
21k views

When is it not appropriate to use the dependency injection pattern?

Since learning (and loving) automated testing I have found myself using the dependency injection pattern in almost every project. Is it always appropriate to use this pattern when working with ...
48
votes
4answers
77k views

What is the point of using DTO (Data Transfer Objects)?

What is the point of using DTO and is it an out dated concept? I use POJOs in the view layer to transfer and persist data. Can these POJOs be considered as an alternative to DTOs?
26
votes
7answers
2k views

The Singleton Pattern [duplicate]

Possible Duplicate: When is Singleton appropriate? I am a new programmer (4 months into my first job) and have recently taken an interest in design patterns. One that I have used recently is ...
25
votes
6answers
5k views

How much business logic should be allowed to exist in the controller layer?

Sometimes we have some business logic represented in the controller code of our applications. This is usually logic that differentiates what methods to call from the model and/or what arguments to ...
9
votes
6answers
1k 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 ...
12
votes
4answers
1k views

Rails: Law of Demeter Confusion

I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this ...
18
votes
3answers
3k 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 ...
11
votes
5answers
41k views

A way to return multiple return values from a method: put method inside class representing return value. Is it a good design?

I need to return 2 values from a method. My approach is as follows: create an inner class with 2 fields that will be used to keep those 2 values put the method inside that class instantiate the ...
10
votes
4answers
1k views

How does thinking on design patterns and OOP practices change in dynamic and weakly-typed languages?

There is a fairly helpful question already along these lines ("Non-OOP Design Patterns?"), but I am more curious about a transitional point of view for someone just getting started with dynamic and ...
10
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1answer
5k views

Software architecture for authentication/access-control of REST web service

I am setting up a new RESTful web service and I need to provide a role-based access control model. I need to create an architecture that will allow users to provide their username and password to get ...
5
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2answers
2k views

Alternative to “inheritance versus composition?” [duplicate]

Possible Duplicate: Where does this concept of “favor composition over inheritance” come from? I have colleagues at work who claim that "Inheritance is an anti-pattern" and want to use ...
16
votes
3answers
1k views

Legitimate “real work” in a constructor?

I am working on a design, but keep hitting a roadblock. I have a particular class (ModelDef) that is essentially the owner of a complex node tree built by parsing an XML schema (think DOM). I want to ...
5
votes
6answers
2k views

Coding style for chained function calls

A common thing you need to do is to take a value, do something with it by passing it to a function, and then do some more with the return value, in a chain. Whenever I run into this type of scenario, ...
4
votes
2answers
492 views

Designing a library that is easy to use: composition or inheritance

I have designed a small library for work that consists of a few exposed classes. These can basically be thought of as a server class and client class. But now that I am writing all the test cases and ...
3
votes
4answers
976 views

Explanation of the definition of interface inheritance as described in GoF book

I am reading the first chapter of the Gof book. Section 1.6 discusses about class vs interface inheritance: Class versus Interface Inheritance It's important to understand the difference between ...
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vote
1answer
602 views

How do we structure our JavaScript so that it is easily editable, testable, and can make calls to render a view without knowing specifics about it?

I am working on a web application that displays some data and uses JavaScript. Right now, we are serving up parts of our JavaScript code (to display certain types of information, that is, "Render a ...