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

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Usage of “Passive View” for winforms application

I'm currently working on a winforms project which will have a rather complex structure with about 300/400 controls which I will have to access during the program is running. I am contemplating the ...
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1answer
70 views

Within an interface specified by a core component, should it request IReadOnlyCollection or IEnumerable?

In thinking about the principle of "be conservative in what you send and liberal in what you accept", I generally try to make my methods receive IEnumerable parameters, but emit a IReadOnlyCollection (...
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2answers
174 views

How to organize and label methods intended for debug?

I have a class System, which uses a bunch of other classes, to achieve some complex signal processing. In debugging System, one needs to observe the output signal for patterns. This is not achievable ...
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3answers
201 views

What to do if I need more than one base class in C#? [closed]

Let's say I have a grid with square fields. For the fields I have an abstract Field class. This class has several subclasses, for example EmptyField or RoadField. Some of these fields can be connected ...
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1answer
125 views

Lower class count vs explicitness

To help with an application that manipulates and works from an XML structure to produce other information, I've created a class structure that closely follows the XML structure. So, the XML is: <...
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7answers
12k views

Should interface names begin with an “I” prefix?

I have been reading "Clean Code" by Robert Martin to hopefully, become a better programmer. While none of it so far has been really ground breaking it has made me think differently about the way I ...
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1answer
53 views

Package Interfaces - Coupling & Re-Usability

Intent Packages should be designed to perform a single function well. Ideally this means that they should be highly modular and different packages should be able to be 'plugged-in' simply by ...
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1answer
295 views

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 ...
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1answer
255 views

Why covariance is forbidden for abstract class in C#

I've been digging in covariance and contravariance in C# and there is one thing I could not manage to understand. C# (AFAIK, as of 4 version) allows one to declare the covariant or contravariant ...
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3answers
178 views

When and why would you extract an abstract method from an abstract class to an interface?

I have been asked the following question in an interview: "What is the need of an interface when you can have an abstract method within an abstract class?" Which I did not know the answer to. Could ...
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1answer
84 views

Use the chance to return booleans after method calls for an optional layer of exception handling? [duplicate]

I would like to ask a follow-up to a question I just asked: Better to have 2 methods with clear meaning, or just 1 dual use method? I now understand why it is best to separate charge(float c); and ...
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6answers
3k views

Better to have 2 methods with clear meaning, or just 1 dual use method?

To simplify the interface, is it better to just not have the getBalance() method? Passing 0 to the charge(float c); will give the same result: public class Client { private float bal; float ...
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1answer
252 views

Open / Closed Principle

I found this code example explaining Open / Closed principle. Code before application of principle: public class Logger { public void Log(string message, LogType logType) { switch (...
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57 views

Software Architecture: CQRS and port modeling

I have a PersonComponent, which an internal implementation is based on CQRS pattern. So which one is better way to model ports (and their interfaces): I'm not totally sure that how high or low -...
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3answers
20k views

Why does C# allow properties in interfaces?

In C#, the following code is valid interface I{ int property{get;set;} } Which doesn't make any sense to me. This seems to break one of the most important principles of interfaces: lack of ...
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3answers
1k views

Is using interfaces for datatypes an anti-pattern?

Suppose I have a various entities in my model (using EF), say User, Product, Invoice and Order. I am writing a user control that can can print the summaries of entity objects in my application where ...
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1answer
230 views

Neat way on passing interface parameter to a constructor

Having lots of Interface that needs to pass in a constructor looks messy, is there any neat way of doing it? Code snippet: public class Foo { private readonly IRepository1 _repository1; ...
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2answers
114 views

Does an interface including several methods that return instances of Object make sense?

I am in the process of writing my first true API. In the process, I am defining an interface for mapping complex data structures onto other complex data structures. At the moment, the interface ...
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1answer
252 views

Why are interfaces necessary in MVP design pattern?

I am trying to understands MVP using Winforms. I found this example. Why do UserModel and UserView need to implement the IUserModel and IUserView interfaces ?
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2answers
93 views

Where to inject dependency required by all implementors of an interface?

I have an interface whose job is to communicate with repository (that implements some interface). It doesn't seem to make sense to implement this interface without receiving a repository,so I'd like ...
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3answers
827 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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1answer
143 views

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
306 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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2answers
77 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
487 views

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
206 views

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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2answers
318 views

Handling interface segregation in C++

I'm designing a "view" handling system for a game. The goal is to be able to have different "views" that can be shown in sequence or stacked on-top of each other. For example, the initial splash ...
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3answers
125 views

Interface design - Parameter choice

Situation: Is it better to have one or few parameters that supply more than enough information for the intended process or should you have more specific parameters that provide just enough ...
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6answers
186 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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4answers
522 views

Implements > extends, but what about variables?

It's preferable to write programs that depend on interfaces rather than on superclasses, but what if you want a class to have certain variables? Sometimes you want a class to implement a certain ...
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2answers
352 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
2k 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 ...
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2answers
228 views

Is Dependency Inversion a valid alternative to the pImpl idiom?

If I want to present to the user of my code an interface, that is unlikely to change, I can write only the public part of the classes in public headers and have a single private pointer to another ...
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3answers
216 views

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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10answers
6k views

Declaring interface in the same file as the base class, is it a good practice?

To be interchangable and testable, normally services with logic needs to have interface, e.g. public class FooService: IFooService { ... } Design-wise, I agree with this, but one of the things ...
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1answer
174 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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4answers
386 views

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
118 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
232 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'...
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3answers
150 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
471 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
331 views

Design interface for WebService to access several MySQL databases

I am currently trying to design an interface for a WebService that can access several MySQL databases. There will be 4 operations available, Add(), Read(), Update() and Delete(). The WebService just ...
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2answers
622 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 ...
4
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1answer
245 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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Text based command/interface design

When using inter-process communication (pipes, memory streams, ...), I typically have a byte stream to communicate, also with http (unless using some heavy-weight web framework), the body comes as a ...
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2answers
211 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
100 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
144 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
150 views

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
411 views

Is this a pattern? Proxy/delegation of interface to existing concrete implementation

I occasionally write code like this when I want to replace small parts of an existing implementation: public interface IFoo { void Bar(); } public class Foo : IFoo { public void Bar() { ...