Questions tagged [interfaces]

Questions about interface related design considerations, such as programming to the interface.

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Can I enforce the overriding of GetHashCode() and Equals() methods for users of a generic container class?

I have a container class similar to the one below (with much of the logic omitted): class Container<T> { Dictionary<T, TWrapped> contains = new Dictionary<T, TWrapper>(); ...
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3answers
369 views

How can I sell DRY? [closed]

Where I work we have around 10 VS projects in a solution which are identical in functionality (with some different different rules in a few methods) and share many exact methods. They share the same ...
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1answer
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Structuring projects in a solution for interfaces

I had this idea that I would achieve some good automation and separation of concerns as follows: Define an interface, IDataProvider, in a class in a DataMuncher project that needs to both consume and ...
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2answers
102 views

Where to put configuration constants?

Considering a small embedded C project, how to decide if certain constants belong to a global configuration file the header of the "module == compilation unit" on top of the the actual C file or ...
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2answers
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Interface Segregation Principle: What to do if interfaces have significant overlap?

From Agile Software Development, Principles, Patterns, and Practices: Pearson New International Edition: Sometimes, the methods invoked by different groups of clients will overlap. If the overlap ...
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2answers
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Programming to Data Oriented Interfaces

There is a portion of our codebase written in the following style: // IScheduledTask.cs public interface IScheduledTask { string TaskName { get; set; } int TaskPriority { get; set; } List&...
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6answers
739 views

If Class is to define attributes and methods, and Interface is to define (a set of) methods, then how to think of interface needing new attributes?

I thought a class is supposed to define, or give a blueprint, of attributes and methods for an object. And then, an interface is to provide a set of methods, as a contract for its clients. (and so a ...
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2answers
383 views

How and when did it happen that, a type is an interface?

I came from a highly functional and procedural background in programming, and never knew that a type is the same as an interface. As in the Design Patterns book by GoF, it says: A type is a name ...
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5answers
14k views

Implementing an interface when you don't need one of the properties

Pretty straight-forward. I'm implementing an interface, but there's one property that is unnecessary for this class and, in fact, shouldn't be used. My initial idea was to just do something like: int ...
4
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1answer
913 views

When should interface be owned by client?

In Agile Software Development: Principles, Patterns, and Practices, Uncle Bob talks about client owning the service interface. My questions are : Should client always own the interface or only ...
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3answers
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What is the purpose of a wrapper class that does nothing but delegate to the object it wraps?

The specific example I have in mind is javax.servlet.ServletResponseWrapper: public class ServletResponseWrapper implements ServletResponse { private ServletResponse response; /** * The ...
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3answers
335 views

How to “program to an interface”

I've read these questions: Understanding "programming to an interface" What is the point of an interface? Does it always make sense to "program to an interface" in Java? I don't ...
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4answers
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In C#, what is the benefit of assigning a class variable to an interface variable before calling any methods?

Where I work we develop in C# .NET and I was looking a code that they have made (my job is to optimize it) but I saw something in particular: Assuming that InterfaceDHO is an interface and ClassDHO ...
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2answers
181 views

Best practice for encapsulating a parameter that requires multiple interfaces to be implemented

I encounter this issue multiple times, but I'm never sure how best to deal with it. Basically, some methods I write require the implementing object to support multiple interfaces. The example I have ...
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3answers
17k views

Generics vs common interface?

I don't remember when I wrote generic class last time. Every time I think I need it after some thinking I make a conclusion I don't. The second answer to this question made me to ask for ...
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3answers
3k views

Communicating to an Object from another without coupling in java?

So I have a Person object, and a GumballMachine object. The behavior I'm searching for is, in the intent to avoid unnecessary coupling, have the method insertCoin() called from within the Person ...
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3answers
4k views

Composition over inheritance but

I'm trying to teach myself software engineering and coming up against some conflicting information which is confusing me. I've been learning OOP and what abstract classes / Interfaces are and how to ...
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2answers
6k views

Should the main method be separate in a separate class? [closed]

In Java main methods often do little more than parsing the command line arguments and initializing an object that then takes over, for example: public class FooServer { // ... public static ...
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1answer
1k views

UML: Should an asynchronous request-response message exchange be modelled as two ports/interfaces or one

I want to model an asynchronous request-response message exchange in UML. The request is sent from a client to a server. The server responses asynchronously. This can be modelled in a component ...
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2answers
256 views

To god (class) or not to god? [duplicate]

I'm working on a project that requires several different users in the system, all of which have overlapping responsibilities; we've isolated two possible ways of tackling this problem, but we're ...
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1answer
228 views

When designing input interfaces for a library, when to use data class rather than data interface?

Let's say library A, B and C are all custom math libraries. They may or may not use the same data types. The libraries have methods that accept data type inputs like ProcessAsync(DataTypeA) or ...
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1answer
185 views

Interface Design: Specific vs General parameter (A Minimal design vs anticipated use variation)

Code public interface IVehicle { string VehicleMake { get; } int MonthsSincePurchase { get; } bool IsApprovedUsed { get; } ... } public class WarrantyPopUpHandler { virtual bool ...
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1answer
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Why can't I return an implementation of an interface for a method that requests the interface? [closed]

I am implementing an interface I on a class A. Class A implements I. I have an Iterator T that is supposed to return an object which implements I everytime I call next. My iterator goes as follows (...
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2answers
1k views

What are the justifications for annotations in a programming language? [closed]

After spending a great deal of time writing C# and looking at Java, it seems to me that annotations are just an ugly code smell that introduce another conceptual layer that could easily be replaced by ...
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1answer
457 views

Coding to an interface vs more generic interfaces

I have a number of classes (and interfaces) which 'code to an interface' interface File { ... } interface FileConverter { public function convert(File $file); //coding to an interface ...
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1answer
183 views

Reusing an interface or method chaining

I am learning about coding to an interface in OOP programming. I understand you should code to an interface so you can 'swap out' functionality. However, I have a situation where I feel I can reuse ...
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4answers
3k views

How is an interface used in Dependency Injection?

I'm working on a simple DI library, and on the subject of using services through interfaces, I can't find the usefulness. Perhaps it's because I dont fully or properly understand how an interface ...
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1answer
217 views

Using own ArrayList in general purpose C libraries, but allowing a different implementation

I've written a couple of libraries since beginning to use C again last year. One thing that still needs addressing in both of these is the correct use of array-based lists - hereafter, ArrayLists. At ...
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1answer
70 views

MVC .NET APP Program Structure [closed]

I am just building a MVC .NET application, eventually this will use entity framework and the repository pattern to structure the program. The first release however will only be calling other jobs that ...
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2answers
288 views

Better application design - where to place interfaces

Where to place interfaces in a typical multi-layered app with DataAccess, BusinessLogic and an Endpoint modules? I propose 2 options In both cases there's only dependency from abstractions, but in ...
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3answers
1k views

Manual Dependency Injection Examples Still Tightly Coupled

I've been using AutoFac for some time now to take care of the dependency injection we're using in a web project. All is well, but I now want to demonstrate DI outside of an AutoFac context for reasons ...
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1answer
59 views

How do I use type assertions in Go when returning an interface type?

A struct I'm working on called fieldDefinition holds metadata about a field used by an object in my web app. One of the fields on fieldDefinition (it does get a bit confusing) looks something like ...
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4answers
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Should an application configuration interface be broken into multiple interfaces to reduce feature creep?

My windows service is neatly separated into 5 components - each with their own interface and pulled together by a bootstrapper. One of my requirements is to provide configuration options in my app....
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1answer
82 views

Should I separate the interface or use single one [closed]

I'm developing a game, I will generate objects. I have create an interface called IObject which has the following properties: String tag // Tag for the object Vector3 position // Where the element is ...
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4answers
762 views

Design: Lisp (or other scripting language) as an interactive interface for C++?

I'm working on a medium size C++ project (will probably end up around 50k lines) and I have to provide an interactive terminal interface. The program produces scientific data as an output and the ...
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2answers
1k views

Could changing the return type from void to string introduce breaking changes?

This SDK have an interface like this: public interface Contract { void update(..); void action(..); void delete(..); } Now, we need to change it to something like this: public ...
4
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4answers
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Design strategy for wrapping exceptions

I'm implementing a type of Repository for a framework/library that has (roughly) the following: public interface FooRepository { boolean contains(String id); Foo fetch(String id); void ...
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1answer
252 views

Inefficient use of interfaces in OOP (C#)

In my code, I've got two interfaces, let's say IOpenable and IExaminable. IOpenable allows the user to Open or Close the object, and IExaminable allows the user to Examine the object. Now, we have ...
2
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1answer
244 views

Define an object with the interface as a type instead of class name [duplicate]

I try to practice with the design patterns and explore one of the possible implementations of the Observer Design Pattern in Java. I paid attention, that in this example the object is defined with the ...
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2answers
649 views

Optional features: default method or separated interface

Dedicated interfaces seems to be a good way to expose the optional features in a domain-specific type hierarchy. However, they impede the use of decorator and composite patterns, which is also common ...
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3answers
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Is an interface considered 'empty' if it inherits from other interfaces?

Empty interfaces are generally consider bad practice, as far as I can tell - especially where things like attributes are supported by the language. However, is an interface considered 'empty' if it ...
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2answers
62 views

Declaring 'chained' interface inheritance

I assume this is largely language-agnostic, but I'm working in C# if it's not Let's say interface I3 inherits from I2, which in turn inherits from I1. I could write this: interface I1 { ... } ...
3
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1answer
193 views

Interfaces, abstraction, coding to an interface

Original question here I am learning OOP and SOLID. I have a 'main' class that performs some actions after reading variables from a config file. This 'main' class is not the focus of this question ...
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2answers
947 views

Convert this abstract class to an interface

I have a security method I would like to be able to sprinkle into other classes throughout my program. It is currently an abstract class but I feel it would be more appropriate as an interface. Can ...
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2answers
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UnsupportedOperationException in java collections framework interfaces

Looking through the Java Collections Framework, I've noticed quite a few of the interfaces have the comment (optional operation). These methods allow implementing classes to through an ...
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2answers
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Advantages of these recommendations in ooprogramming using Java

Below are the recommendation from section 5.1 of this essay. While Java is not a pure object-oriented language, it is possible to program in a pure object-oriented style by obeying the following ...
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3answers
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Why List<E> interface is additionally introduced in collection hierarchy? [duplicate]

Below is the diagram, where, if we just consider the implementations of List, AbstractList maintains the core behavior of list. To introduce the new implementation class MyList(say) one can inherit ...
3
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1answer
777 views

Creating an interface just to decouple from third party libraries

I'm currently developing the Authorization module on a framework of mine. I have the following class so far: public interface IAuthorizationManager<C> where C : ...
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1answer
85 views

What would this interface be called? [closed]

At work we have a java backend that talks to python on some mobile devices. The mobile devices have no GUI, it's just pure string manipulation. All contact is initiated by the python; the java is just ...
2
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1answer
146 views

How valuable is decoupling in proprietary software?

When developing with Symfony2 PHP framework I often see reccomendations to decouple code but most of the time that is accompanied by a 'if you want to release as a third party bundle'. Which begs the ...