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  • Does C++ have a proper implementation of interface that does not use vtable?

    - by gilbertc
    Does C++ have a proper implementation of interface that does not use vtable? for example class BaseInterface{ public: virtual void func() const = 0; } class BaseInterfaceImpl:public BaseInterface{ public: void func(){ std::cout<<"called."<<endl; } } BaseInterface* obj = new BaseInterfaceImpl(); obj->func(); the call to func at the last line goes to vtable to find the func ptr of BaseInterfaceImpl::func, but is there any C++ way to do that directly as the BaseInterfaceImpl is not subclassed from any other class besides the pure interface class BaseInterface? Thanks. Gil.

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  • Does C++ have a static polymorphism implementation of interface that does not use vtable?

    - by gilbertc
    Does C++ have a proper implementation of interface that does not use vtable? for example class BaseInterface{ public: virtual void func() const = 0; } class BaseInterfaceImpl:public BaseInterface{ public: void func(){ std::cout<<"called."<<endl; } } BaseInterface* obj = new BaseInterfaceImpl(); obj->func(); the call to func at the last line goes to vtable to find the func ptr of BaseInterfaceImpl::func, but is there any C++ way to do that directly as the BaseInterfaceImpl is not subclassed from any other class besides the pure interface class BaseInterface? Thanks. Gil.

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  • Casting as Interface? Awesome.

    - by cam
    I was just experimenting around with one of my programs, trying to make it looks prettier and I found something interesting. I have an interface that 4 classes inherit from. I found that if I pass the Class as an object to a method like so: ClassTest classtest = new ClassTest(); DoOperation(classtest); private void DoOperation(object o) { ((InterfaceClass)o).DoThis(); } So I can pass any type of class that inherits from InterfaceClass, and it will preform the proper interface operation? This is the coolest thing I've ever found from OOP (something I've never really studied) I really thought interfaces were created for the sole purpose of organization for developers. Are there more uses for interfaces than this?

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  • What's is the point of PImpl pattern while we can use interface for same purpose in C++?

    - by ZijingWu
    I see a lot of source code which using PIMPL idiom in C++. I assume Its purposes are hidden the private data/type/implementation, so it can resolve dependence, and then reduce compile time and header include issue. But interface class in C++ also have this capability, it can also used to hidden data/type and implementation. And to hidden let the caller just see the interface when create object, we can add an factory method in it declaration in interface header. The comparison is: Cost: The interface way cost is lower, because you doesn't even need to repeat the public wrapper function implementation void Bar::doWork() { return m_impl->doWork(); }, you just need to define the signature in the interface. Well understand: The interface technology is more well understand by every C++ developer. Performance: Interface way performance not worse than PIMPL idiom, both an extra memory access. I assume the performance is same. Following is the pseudocode code to illustrate my question: // Forward declaration can help you avoid include BarImpl header, and those included in BarImpl header. class BarImpl; class Bar { public: // public functions void doWork(); private: // You doesn't need to compile Bar.cpp after change the implementation in BarImpl.cpp BarImpl* m_impl; }; The same purpose can be implement using interface: // Bar.h class IBar { public: virtual ~IBar(){} // public functions virtual void doWork() = 0; }; // to only expose the interface instead of class name to caller IBar* createObject(); So what's the point of PIMPL?

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  • UML interface: URL iframe integration

    - by Bernd
    I have two applications, A and B, both with a web-based user interface. Both applications are integrated via an URL iframe mechanism. A user can click on a link in application A and then gets the UI of application B as am iframe in application A. Now, since both applications have an interface between each other (do they?): Who provides the interface and who requires the interface, in the UML sense? What is the main information flow on this interface?

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  • What's the proper way to setup different objects as delegates using Interface Builder?

    - by eagle
    Let's say I create a new project. I now add two text fields to the view controller in Interface Builder. I want to respond to delegate events that the text fields create, however, I don't want to have the main view controller to act as the delegate for both text fields. Ideally I want a separate file for each text field that acts as the delegate. Each of these objects also needs to be able to interact with the main view controller. My question is how I would set this up and link everything correctly? I tried creating a new class that inherits from NSObject and implements UITextFieldDelegate. I then added an instance variable called "viewController" of the same type of my view controller and marked it with IBOutlet (this required me to add #import "myViewcontroller.h"). I then went to Interface Builder and opened up my view controller which contains the two edit boxes. I added an NSObject to the form and changed it's type to be of the new class I created. I set its viewController property to the File's Owner, and set one of the textbox's delegate properties to point to this new object I created. Now when I run the program, it crashes when I touch the text box. It gives the error EXC_BAD_ACCESS. I'm guessing I didn't link stuff correctly in IB. Some things I'm not sure about which might be the problem: Does IB automatically know to create an instance of the class just by placing the NSObject in the ViewController? Can it properly assign the viewController property to an instance of itself even though it is creating itself at the same time?

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  • When using Data Annotations with MVC, Pro and Cons of using an interface vs. a MetadataType

    - by SkippyFire
    If you read this article on Validation with the Data Annotation Validators, it shows that you can use the MetadataType attribute to add validation attributes to properties on partial classes. You use this when working with ORMs like LINQ to SQL, Entity Framework, or Subsonic. Then you can use the "automagic" client and server side validation. It plays very nicely with MVC. However, a colleague of mine used an interface to accomplish exactly the same result. it looks almost exactly the same, and functionally accomplishes the same thing. So instead of doing this: [MetadataType(typeof(MovieMetaData))] public partial class Movie { } public class MovieMetaData { [Required] public object Title { get; set; } [Required] [StringLength(5)] public object Director { get; set; } [DisplayName("Date Released")] [Required] public object DateReleased { get; set; } } He did this: public partial class Movie :IMovie { } public interface IMovie { [Required] object Title { get; set; } [Required] [StringLength(5)] object Director { get; set; } [DisplayName("Date Released")] [Required] object DateReleased { get; set; } } So my question is, when does this difference actually matter? My thoughts are that interfaces tend to be more "reusable", and that making one for just a single class doesn't make that much sense. You could also argue that you could design your classes and interfaces in a way that allows you to use interfaces on multiple objects, but I feel like that is trying to fit your models into something else, when they should really stand on their own. What do you think?

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  • Is there anything like Unity for simple things that don't require an interface?

    - by Dave
    Perhaps I'm misapplying Unity, but here goes. I have a couple of applications, both of which load the same plugin assemblies. All assemblies require a library, and I want them to be able to access this library via Unity. However, in order to use Unity, or any other IoC framework, I'd have to write an interface for this library. I will probably do this, but since an interface isn't really needed for anything other than to support Unity, I am afraid that this means that I am 1) missing the point, or 2) misapplying the framework. If I avoid something that offers me DI, then I'd have to make the library class a singleton, and then pass it to all of the plugin constructors, or via a public property, and I don't want to do this. That said, and without actually implementing anything with Unity yet, I'm not getting one other detail -- although Unity will let me request the library via Resolve<, my plugins will still need to have a reference to the Unity instance that is created in the main applications. So is this a case where your only option is to pass the Unity reference to all of the plugins, but then it's convenient from that point on, merely because you can use Unity to get at all of the other dependencies?

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  • make local only daemon listening on different interface (using iptables port forwarding)?

    - by UniIsland
    i have a daemon program which listens on 127.0.0.1:8000. i need to access it when i connect to my box with vpn. so i want it to listen on the ppp0 interface too. i've tried the "ssh -L" method. it works, but i don't think it's the right way to do that, having an extra ssh process running in the background. i tried the "netcat" method. it exits when the connection is closed. so not a valid way for "listening". i also tried several iptables rules. none of them worked. i'm not listing here all the rules i've used. iptables -A FORWARD -j ACCEPT iptables -t nat -A PREROUTING -i ppp+ -p tcp --dport 8000 -j DNAT --to-destination 127.0.0.1:8000 the above ruleset doesn't work. i have net.ipv4.ip_forward set to 1. anyone knows how to redirect traffic from ppp interface to lo? say, listen on "192.168.45.1:8000 (ppp0)" as well as "127.0.0.1:8000 (lo)" there's no need to alter the port. thanx

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  • What would be the safest way to store objects of classes derived from a common interface in a common

    - by Svenstaro
    I'd like to manage a bunch of objects of classes derived from a shared interface class in a common container. To illustrate the problem, let's say I'm building a game which will contain different actors. Let's call the interface IActor and derive Enemy and Civilian from it. Now, the idea is to have my game main loop be able to do this: // somewhere during init std::vector<IActor> ActorList; Enemy EvilGuy; Civilian CoolGuy; ActorList.push_back(EvilGuy); ActorList.push_back(CoolGuy); and // main loop while(!done) { BOOST_FOREACH(IActor CurrentActor, ActorList) { CurrentActor.Update(); CurrentActor.Draw(); } } ... or something along those lines. This example obviously won't work but that is pretty much the reason I'm asking here. I'd like to know: What would be the best, safest, highest-level way to manage those objects in a common heterogeneous container? I know about a variety of approaches (Boost::Any, void*, handler class with boost::shared_ptr, Boost.Pointer Container, dynamic_cast) but I can't decide which would be the way to go here. Also I'd like to emphasize that I want to stay away as far as possible from manual memory management or nested pointers. Help much appreciated :).

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  • How to Implement an Interface that Requires Duplicate Member Names?

    - by Will Marcouiller
    I often have to implement some interfaces such as IEnumerable<T> in my code. Each time, when implementing automatically, I encounter the following: public IEnumerator<T> GetEnumerator() { // Code here... } public IEnumerator GetEnumerator1() { // Code here... } Though I have to implement both GetEnumerator() methods, they impossibly can have the same name, even if we understand that they do the same, somehow. The compiler can't treat them as one being the overload of the other, because only the return type differs. When doing so, I manage to set the GetEnumerator1() accessor to private. This way, the compiler doesn't complaint about not implementing the interface member, and I simply throw a NotImplementedException within the method's body. However, I wonder whether it is a good practice, or if I shall proceed differently, as perhaps a method alias or something like so. What is the best approach while implementing an interface such as IEnumerable<T> that requires the implementation of two different methods with the same name? EDIT #1 Does VB.NET reacts differently from C# while implementing interfaces, since in VB.NET it is explicitly implemented, thus forcing the GetEnumerator1(). Here's the code: Public Function GetEnumerator() As System.Collections.Generic.IEnumerator(Of T) Implements System.Collections.Generic.IEnumerable(Of T).GetEnumerator // Code here... End Function Public Function GetEnumerator1() As System.Collections.Generic.IEnumerator Implements System.Collections.Generic.IEnumerable.GetEnumerator // Code here... End Function Both GetEnumerator() methods are explicitly implemented, and the compile will refuse them to have the same name. Why?

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  • Is it advisable to have an interface as the return type?

    - by wb
    I have a set of classes with the same functions but with different logic. However, each class function can return a number of objects. It is safe to set the return type as the interface? Each class (all using the same interface) is doing this with different business logic. protected IMessage validateReturnType; <-- This is in an abstract class public bool IsValid() <-- This is in an abstract class { return (validateReturnType.GetType() == typeof(Success)); } public IMessage Validate() { if (name.Length < 5) { validateReturnType = new Error("Name must be 5 characters or greater."); } else { validateReturnType = new Success("Name is valid."); } return validateReturnType; } Are there any pitfalls with unit testing the return type of an function? Also, is it considered bad design to have functions needing to be run in order for them to succeed? In this example, Validate() would have to be run before IsValid() or else IsValid() would always return false. Thank you.

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  • How to Implement an Interface that Requires Duplicate Member Names in C#?

    - by Will Marcouiller
    I often have to implement some interfaces such as IEnumerable<T> in my code. Each time, when implementing automatically, I encounter the following: public IEnumerator<T> GetEnumerator() { // Code here... } public IEnumerator GetEnumerator1() { // Code here... } Though I have to implement both GetEnumerator() methods, they impossibly can have the same name, even if we understand that they do the same, somehow. The compiler can't treat them as one being the overload of the other, because only the return type differs. When doing so, I manage to set the GetEnumerator1() accessor to private. This way, the compiler doesn't complaint about not implementing the interface member, and I simply throw a NotImplementedException within the methods body. However, I wonder whether it is a good practice, or if I shall proceed differently, as perhaps a method alias or something like so. What is the best approach while implementing an interface such as IEnumerable<T> that requires the implementation of two different methods with the same name?

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  • C# What is the best way to determine the type of an inherited interface class?

    - by Martijn
    In my application I work with criterias. I have one base Criteria interface and and other interfaces who inherits from this base interface: ICriteria | | ---------------------- | | ITextCriteria IChoices What I'd like to know is, what is the best way to know what Type the class is? In my code I have a dropdown box and based on that I have to determine the type: // Get selected criteria var selectedCriteria = cmbType.SelectedItem as ICriteria; if (selectedCriteria is IChoices) { //selectedCriteria = cmbType.SelectedItem as IChoices; Doesn't work IChoices criteria = selectedCriteria as IChoices;//cmbType.SelectedItem as IChoices; SaveMultipleChoiceValues(criteria); //_category.AddCriteria(criteria); } else { //ICriteria criteria = selectedCriteria; //cmbType.SelectedItem as ICriteria; if (selectedCriteria.GetCriteriaType() == CriteriaTypes.None) { return; } //_category.AddCriteria(criteria); } _category.AddCriteria(selectedCriteria); selectedCriteria.LabelText = txtLabeltext.Text; this.Close(); My question is, is this the best way? Or is there a better way to achieve this? The chance is big that there are coming more interfaces based on ICriteria.

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  • Making an interface for input in C - How?

    - by tloszk
    I have a big question. I started to develop a simple 3D engine (or should I call it framework?). I use OpenGL for rendering and it is developed for Windows. It is all written in C. But I don't know, how to write an "interface" for the keyboard/mouse input. I would like to keep it as simple as possible and nice - what the Win32 "native" input system is not. If anyone has suggestions about the topic, please, tell me. Thanks for everyone, who answers to my question!

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  • Where and how to reference composite MVP components?

    - by Lea Hayes
    I am learning about the MVP (Model-View-Presenter) Passive View flavour of MVC. I intend to expose events from view interfaces rather than using the observer pattern to remove explicit coupling with presenter. Context: Windows Forms / Client-Side JavaScript. I am led to believe that the MVP (or indeed MVC in general) pattern can be applied at various levels of a user interface ranging from the main "Window" to an embedded "Text Field". For instance, the model to the text field is probably just a string whereas the model to the "Window" contains application specific view state (like a persons name which resides within the contained text field). Given a more complex scenario: Documentation viewer which contains: TOC navigation pane Document view Search pane Since each of these 4 user interface items are complex and can be reused elsewhere it makes sense to design these using MVP. Given that each of these user interface items comprises of 3 components; which component should be nested? where? who instantiates them? Idea #1 - Embed View inside View from Parent View public class DocumentationViewer : Form, IDocumentationViewerView { public DocumentationViewer() { ... // Unclear as to how model and presenter are injected... TocPane = new TocPaneView(); } protected ITocPaneView TocPane { get; private set; } } Idea #2 - Embed Presenter inside View from Parent View public class DocumentationViewer : Form, IDocumentationViewerView { public DocumentationViewer() { ... // This doesn't seem like view logic... var tocPaneModel = new TocPaneModel(); var tocPaneView = new TocPaneView(); TocPane = new TocPanePresenter(tocPaneModel, tocPaneView); } protected TocPanePresenter TocPane { get; private set; } } Idea #3 - Embed View inside View from Parent Presenter public class DocumentationViewer : Form, IDocumentationViewerView { ... // Part of IDocumentationViewerView: public ITocPaneView TocPane { get; set; } } public class DocumentationViewerPresenter { public DocumentationViewerPresenter(DocumentationViewerModel model, IDocumentationViewerView view) { ... var tocPaneView = new TocPaneView(); var tocPaneModel = new TocPaneModel(model.Toc); var tocPanePresenter = new TocPanePresenter(tocPaneModel, tocPaneView); view.TocPane = tocPaneView; } } Some better idea...

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  • RPi and Java Embedded GPIO: Sensor Hardware for Java Enabled Interface

    - by hinkmond
    Now here's the hardware you'll need to make a Java app interface with a static charge sensor connected to your Raspberry Pi via the GPIO port. It means another Fry's run of course. That's not too bad during Christmas since you can browse all the gadget and toys while doing your shopping for sensor hardware for your RPi. Here's a your shopping list: 1 - NTE312 JFET N-channel transistor (this is in place of the MPF-102) 1 - Set of Jumper Wires 1 - LED 1 - 300 ohm resistor 1 - set of header pins Grab all that from Fry's or your local hobby electronics shop and come back here for how to connect it together. Oh, and don't go too crazy buying all the other electronic toys and gadgets that catch your eye because of the holiday displays at the store. Hinkmond

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  • Creating a remote management interface

    - by Johnny Mopp
    I'm looking for info on creating a remote management interface for our software. This is not anything illicit. Our software is for live TV production and once they go on-air we can't access the PC (usually through LogMeIn). I would like to be able to upload/download files and issue commands to our software. The commands would be software specific like "load this file" or "run this script" or "return this value" etc. A socket connection is preferred but the problem is most of our PCs are behind firewalls and NAT servers. I'm not sure where to start. I think HTTP tunneling is the way to go but am wondering if there are other options or recommendations. Also, assume our clients are not willing to open up ports for security reasons. Thanks.

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  • In Search of Automatic ORM with REST interface

    - by Dan Ray
    I have this wish that so far Google hasn't been able to fulfill. I want to find a package (ideally in PHP, because I know PHP, but I guess that's not a hard requirement) that you point at a database, it builds an ORM based on what it finds there, and exposes a REST interface over the web. Everything I've found in my searches requires a bunch of code--like, it wants you to build the classes for it, but it'll handle the REST request routing. Or it does database and relational stuff just fine, but you have to build your own methods for all the CRUD actions. That's dumb. REST is well defined. If I wanted to re-invent the wheel, I totally could, but I don't want to. Isn't there somebody who's built a one-shot super-simple auto-RESTing web service package?

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  • Installing netcdf c++ interface on ubuntu 12.04.1 LTS

    - by iluvatar
    I am using a code which employs the modern netcdf c++ interface (netcdf namespace, include file is called just netcdf without .h or similar, ncFile class, etc) and have just switched to ubuntu 12.04.1 LTS. I installed netcdf and libnetcdf6 with apt-get, but I still get the "old" headers in /usr/local/include (netcdf.h, netcdfcpp.h, etc). In Ubuntu, the library version for netcdf is 4.1.1, while at my own computer with Mac Os X (where I have the right netcdf include file) the version is 4.2.1.1 . I cannot modify the source code I am using. I would like to know if there is a way to upgrade the netcdf library on ubuntu to support the modern c++ ointerface, or, if I have to manually compile it, if you think that using src2pkg is a good idea. This is my first experience with Ubuntu. Thanks in advance.

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  • JMonkeyEngine display a spatial in a Nifty GUI interface

    - by Yanick Rochon
    I want to display a spatial (or the rendering of a spatial/scene) in my HUD interface. I'm really not sure how to go with this. I have search the documentation, but all the queries I search yields no result, and all I could find about images is that one can specify one with the setBackgroundImage method in the builder and setImage from the ImageRenderer class. The latter takes a String or a NiftyImage, but I'm not sure how to create one without loading an image file. Any help to understand this (if even possible) is appreciated. Thanks!

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  • '6' key stuck when outside the graphical interface

    - by Felipe Jacob
    A strange thing has been happening since I installed Ubuntu. Whenever I'm not on the graphical interface, that is, if I do ctrl+alt+f2, or while the system is shutting down, or when I try to reset my password accessing root on security mode, the '6' key seems to be stuck. This doesn't affect my day-to-day usage at all, but whenever I change from the graphical console, I can't do anything because it keeps pressing '666666...'. Does anyone know why that might be happening? My keyboard is a Logitech G710+, and hasn't shown any other possible compatibility issues.

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  • After upgrading to 13.04 Unity interface is not showing

    - by ?????? ?????
    I've upgraded to Raring last night. The upgrade itself went okay, no errors. But when I rebooted the computer afterwards and logged in to my Unity session, all I could see was the Desktop background (together with Desktop icons), and no Unity interface. The Super button shortcut wasn't showing the Dash, there was no top panel etc. Please see the screenshot. As a hint, I'm suspecting it's got something to do with my switchable graphics. I'm running Ubuntu on Acer Aspire AS5830TG with nVidia GT540M and an Intel integrated card. In 12.10 I was using Bumblebee to manage the graphic card switching. During the upgrade I saw something related to nvidia had to be uninstalled, but didn't pay much attention to it. I can't be sure if it has anything to do with my problem though. What could possibly go wrong?

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  • As a tooling/automation developer, can I be making better use of OOP?

    - by Tom Pickles
    My time as a developer (~8 yrs) has been spent creating tooling/automation of one sort or another. The tools I develop usually interface with one or more API's. These API's could be win32, WMI, VMWare, a help-desk application, LDAP, you get the picture. The apps I develop could be just to pull back data and store/report. It could be to provision groups of VM's to create live like mock environments, update a trouble ticket etc. I've been developing in .Net and I'm currently reading into design patterns and trying to think about how I can improve my skills to make better use of and increase my understanding of OOP. For example, I've never used an interface of my own making in anger (which is probably not a good thing), because I honestly cannot identify where using one would benefit later on when modifying my code. My classes are usually very specific and I don't create similar classes with similar properties/methods which could use a common interface (like perhaps a car dealership or shop application might). I generally use an n-tier approach to my apps, having a presentation layer, a business logic/manager layer which interfaces with layer(s) that make calls to the API's I'm working with. My business entities are always just method-less container objects, which I populate with data and pass back and forth between my API interfacing layer using static methods to proxy/validate between the front and the back end. My code by nature of my work, has few common components, at least from what I can see. So I'm struggling to see how I can better make use of OOP design and perhaps reusable patterns. Am I right to be concerned that I could be being smarter about how I work, or is what I'm doing now right for my line of work? Or, am I missing something fundamental in OOP? EDIT: Here is some basic code to show how my mgr and api facing layers work. I use static classes as they do not persist any data, only facilitate moving it between layers. public static class MgrClass { public static bool PowerOnVM(string VMName) { // Perform logic to validate or apply biz logic // call APIClass to do the work return APIClass.PowerOnVM(VMName); } } public static class APIClass { public static bool PowerOnVM(string VMName) { // Calls to 3rd party API to power on a virtual machine // returns true or false if was successful for example } }

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