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  • Having a base class function depend on its child class C#

    - by Junk Junk
    I have a Base class with a method that a child class will almost always override. However, instead of replacing the base class' method entirely, I would like for whatever is derived in the child class to be added to what is already in the base class. For Example: class BaseClass public string str() { var string = "Hello my name is" ; } class ChildClass : BaseClass public override string str(){ var string = "Sam"; } The point is that if I want to access the str() method by creating an instance of the ChildClass, the string will print out as "Hello, my name is Sam". I've been looking around and all I have been finding is that this should NOT happen, as the base class shouldn't even know that it is being inherited. So, if the design is false, how would I go about doing this? Keep in mind that there will be multiple child classes inheriting from BaseClass. Thank you

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  • Sorting NSTableColumn contents

    - by Yahoo
    Hey, I have a problem with sorting NSTableColumn contents. In my NSTableView there are three columns: File, Size, Path. The contents are stored in NSMutableArray. Each object in this array is a NSDictionary containing three keys: file, size and path - value for each is a NSString. In Interface Builder, in each Table Column's attributes I can choose sorting options: Selector: IB entered "compare:" which I think is ok, because I compare NSStrings. Sort Key - and that's the problem I think - I don't know what to enter here. Any clues? If you've got questions about my code, please ask.

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  • Question of using static_cast on "this" pointer in a derived object to base class

    - by Johnyy
    Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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  • fluent interface program in Ruby

    - by intern
    we have made the following code and trying to run it. class Numeric def gram self end alias_method :grams, :gram def of(name) ingredient = Ingredient.new(name) ingredient.quantity=self return ingredient end end class Ingredient def initialize(n) @@name= n end def quantity=(o) @@quantity = o return @@quantity end def name return @@name end def quantity return @@quantity end end e= 42.grams.of("Test") a= Ingredient.new("Testjio") puts e.quantity a.quantity=90 puts a.quantity puts e.quantity the problem which we are facing in it is that the output of puts a.quantity puts e.quantity is same even when the objects are different. what we observed is that second object i.e 'a' is replacing the value of the first object i.e. 'e'. the output is coming out to be 42 90 90 but the output required is 42 90 42 can anyone suggest why is it happening? it is not replacing the object as object id's are different..only the values of the objects are replaced.

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  • fluent interface program in Ruby

    - by intern
    we have made the following code and trying to run it. class Numeric def gram self end alias_method :grams, :gram def of(name) ingredient = Ingredient.new(name) ingredient.quantity=self return ingredient end end class Ingredient def initialize(n) @@name= n end def quantity=(o) @@quantity = o return @@quantity end def name return @@name end def quantity return @@quantity end end e= 42.grams.of("Test") a= Ingredient.new("Testjio") puts e.quantity a.quantity=90 puts a.quantity puts e.quantity the problem which we are facing in it is that the output of puts a.quantity puts e.quantity is same even when the objects are different. what we observed is that second object i.e 'a' is replacing the value of the first object i.e. 'e'. the output is coming out to be 42 90 90 but the output required is 42 90 42 can anyone suggest why is it happening? it is not replacing the object as object id's are different..only the values of the objects are replaced.

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  • A question about entities, roles and interfaces in Entity Framework 4.

    - by mvole
    Hi, I am an experienced .NET developer but new to EF - so please bear with me. I will use an example of a college application to illustrate my problem. I have these user roles: Lecturer, Student, Administrator. In my code I envisage working with these entities as distinct classes so e.g. a Lecturer teaches a collection of Students. And work with 'is Student' 'TypeOf' etc. Each of these entities share lots of common properties/methods e.g. they can all log onto the system and do stuff related to their role. In EF designer I can create a base entity Person (or User...) and have Lecturer, Student and Administrator all inherit from that. The difficulty I have is that a Lecturer can be an Administrator - and in fact on occasion a Student can be a Lecturer. If I were to add other entities such as Employee and Warden then this gets even more of an issue. I could presumably work with Interfaces so a person could implement ILecturer and IStudent, however I do not see how this fits within EF. I would like to work within the EF designer if possible and I'm working model-first (coding in C#). So any help and advice/samples would be very welcome and much appreciated. Thanks

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  • MCV/MVP Patterns and Applications that interface with Hardware (DAQ/PLC/etc)

    - by Ryan
    I've been reading a lot about the MCV and MVP patterns for use with UI and it seems like a really nice powerful way to handle user interfaces. I am - however - having a difficult time deciding how this could integrate into a system where data in the model is created from a Data Acquisition System or Serial/Ethernet devices. There is also the added step that 70% of application interaction is performed by a PLC instead of a live user. It seems that for apps that just read/write & manipulate information from a database this works great, but how does does hardware and automation fit into these patterns? Is it as simple as another controller (for lack of a better term) that interacts with hardware that manipulates data and writes to a model? Maybe I am over thinking this or thinking too simply, so any advice would be great. I'm not quite sure where I'm going with this, so if something doesn't make sense or I was too vague leave me a comment. Thanks!

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  • Is there any ready-made calendar control for iPhone apps?

    - by chester
    I am building an applicaiton for the iPhone that will display upcoming and past events. I settled for a list view, but then I realized that a calendar (just like the one displayed in the "month" view in the built-in Calendar application) would be a best match (that is, this one). However, the iPhone Human Interface Guidelines just mentions the Date Picker, not the calendar, so I believe there is nothing like that out of the box. Is that true? If so, does anyone know of a third-party control that could be used? (I could write one myself, but I'd rather pick up something ready, since this is a departure on the original project plans). Thank you all for your attention.

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  • Different return value of an overridden class

    - by Samer Afach
    I have a simple but confusing question here. Is it legal to have a different return value type for overridden methods than the abstact ones defined in the base class?? I did that and the compiler didn't complain... could someone please explain? class MyBaseClass { int value; public: virtual int getValue() = 0; }; class MyClass : public MyBaseClass { double value; public: virtual double getValue(); // here!!! return is double, not int }; double MyClass::getValue() { return this->value; } The compiler totally accepted something similar (MSVC und MinGW)... could anyone please exaplain to what extent this is legal?

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  • Should I use a metaclass, class decorator, or override the __new__ method?

    - by 007brendan
    Here is my problem. I want the following class to have a bunch of property attributes. I could either write them all out like foo and bar, or based on some other examples I've seen, it looks like I could use a class decorator, a metaclass, or override the __new__ method to set the properties automagically. I'm just not sure what the "right" way to do it would be. class Test(object): def calculate_attr(self, attr): # do calculaty stuff return attr @property def foo(self): return self.calculate_attr('foo') @property def bar(self): return self.calculate_attr('bar')

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  • Is it good practice to put private API in the .m files and public API in .h files in Cocoa?

    - by Paperflyer
    Many of my classes in my current project have several properties and methods that are only ever called from within the class itself. Also, they might mess with the working of the class depending on the current state of the class. Currently, all these interfaces are defined in the main interface declaration in the .h files. Is it considered good practice to put the “private” methods and properties at the top of the .m files? This won't ever affect anything since I am very likely the only person ever to look at this source code, but of course it would be interesting to know for future projects.

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  • C++: Create abstract class with abstract method and override the method in a subclass

    - by Martijn Courteaux
    Hi, How to create in C++ an abstract class with some abstract methods that I want to override in a subclass? How should the .h file look? Is there a .cpp, if so how should it look? In Java it would look like this: abstract class GameObject { public abstract void update(); public abstract void paint(Graphics g); } class Player extends GameObject { @Override public void update() { // ... } @Override public void paint(Graphics g) { // ... } } // In my game loop: for (int i = 0; i < objects.size(); i++) { objects.get(i).update(); } for (int i = 0; i < objects.size(); i++) { objects.get(i).paint(g); } Translating this code to C++ is enough for me.

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  • How to implement image map type interface for a game board in Java 6

    - by Billy
    My group project at school is to implement a style of monopoly in which students can buy courses and land on various squares and move around the board. This is not a regular square board so we were wondering if anyone had any ideas on how we would implement an image map or something like it to create many clickable regions not in a perfect square. I have attached the image of the game board. Just a way to start is needed, not lots of code or anything as we all know java pretty well. If anyone has any ideas that would be great. Image of board is here. http://imgur.com/fH5WC.png

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  • Using member variables inherited from a templated base class (C++)

    - by Aaron Becker
    I'm trying to use member variables of a templated base class in a derived class, as in this example: template <class dtype> struct A { int x; }; template <class dtype> struct B : public A<dtype> { void test() { int id1 = this->x; // always works int id2 = A<dtype>::x; // always works int id3 = B::x; // always works int id4 = x; // fails in gcc & clang, works in icc and xlc } }; gcc and clang are both very picky about using this variable, and require either an explicit scope or the explicit use of "this". With some other compilers (xlc and icc), things work as I would expect. Is this a case of xlc and icc allowing code that's not standard, or a bug in gcc and clang?

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  • Java method get the inheriting type

    - by DrDro
    I have several classes that extend C and I would need a method that accepts any argument of type C. But in this method I would like to know if I'm dealing with A or B. * public A extends C public B extends C public void goForIt(C c)() If I cast how can I retrieve the type in a clean way (I just read using getClass or instanceof is often not the best way). PS: Fell free to edit an explicit title. *Sorry but I can't type closing braces

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  • Why can't I expose an interface in a .NET asmx web service?

    - by mcliedtk
    I have a .NET web service (using asmx...have not upgraded to WCF yet) that exposes the following: public class WidgetVersion1 : IWidget {} public class WidgetVersion2 : IWidget {} When I attempt to bind to the web service, I get the following serialization error: Cannot serialize member WidgetVersion1 of type IWidget because it is an interface. I have tried adding various attributes to the IWidget interface (XmlIgnore, SoapIgnore, NonSerialized), but they are not valid on an interface. Does anyone know why I am unable to expose the interface? I assume WSDL does not support interfaces, but couldn't .NET get around this by simply not serializing the interface? Are there any ways around this apart from removing the IWidget interface from the WidgetVersion1 and WidgetVersion2 class definitions?

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  • Session is null when inherit from System.Web.UI.Page

    - by Andreas K.
    I want to extend the System.Web.UI.Page-class with some extra stuff. In the ctor I need the value of a session-variable. The problem is that the Session-object is null... public class ExtendedPage : System.Web.UI.Page { protected foo; public ExtendedPage() { this.foo = (int)HttpContext.Current.Session["foo"]; // NullReferenceException } } If I move the part with the session-object into the Load-Event everything works fine... public class ExtendedPage : System.Web.UI.Page { protected foo; public ExtendedPage() { this.Load += new EventHandler(ExtendedPage_Load); } void ExtendedPage_Load(object sender, EventArgs e) { this.foo = (int)HttpContext.Current.Session["foo"]; } } Why is the Session-object null in the first case??

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  • Best way to insert items from a Derived class's constructor into a Base class's private std::vector?

    - by Will
    I have these classes: class Base { ... private: std::vector<X> v; }; class Derived { Derived(X*, int n); } where the constructor of Derived is passed an array of item Xs, which I need to insert into my vector v in the Base class. (X is a smart pointer) Currently I see two ways to do this: 1) Create a function in Base: InsertItem(X*) that will insert an item into the vector. 2) Create a vector in Derived that contains the full list, then get it into Base by moving the entire vector. I dont see any advantages to #2, but was wondering if #1 was a good solution, or if there are better ways to do this. Thanks!

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  • Apples, oranges, and pointers to the most derived c++ class

    - by Matthew Lowe
    Suppose I have a bunch of fruit: class Fruit { ... }; class Apple : public Fruit { ... }; class Orange: public Fruit { ... }; And some polymorphic functions that operate on said fruit: void Eat(Fruit* f, Pesticide* p) { } void Eat(Apple* f, Pesticide* p) { ingest(f,p); } void Eat(Orange* f, Pesticide* p) { peel(f,p); ingest(f,p); } OK, wait. Stop right there. Note at this point that any sane person would make Eat() a virtual member function of the Fruit classes. But that's not an option, because I am not a sane person. Also, I don't want that Pesticide* in the header file for my fruit class. Sadly, what I want to be able to do next is exactly what member functions and dynamic binding allow: typedef list<Fruit*> Fruits; Fruits fs; ... for(Fruits::iterator i=fs.begin(), e=fs.end(); i!=e; ++i) Eat(*i); And obviously, the problem here is that the pointer we pass to Eat() will be a Fruit*, not an Apple* or an Orange*, therefore nothing will get eaten and we will all be very hungry. So what I really want to be able to do instead of this: Eat(*i); is this: Eat(MAGIC_CAST_TO_MOST_DERIVED_CLASS(*i)); But to my limited knowledge, such magic does not exist, except possibly in the form of a big nasty if-statement full of calls to dynamic_cast. So is there some run-time magic of which I am not aware? Or should I implement and maintain a big nasty if-statement full of dynamic_casts? Or should I suck it up, quit thinking about how I would implement this in Ruby, and allow a little Pesticide to make its way into my fruit header?

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  • NET USE command And Network Provider interface.

    - by Benjamin
    When we command "net use" on command prompt, the result has four columns. Status Local Remote Network OK Z: \\10.x.x.x\Public Microsoft Windows Network X: \\10.y.y.y\Public My Network Redirector The Microsoft Windows Network(SMB)'s Status has OK value, but we don't. It's just empty. We implemented NPEnumResource function in our Network Provider dll. But I don't know how can I set the value(OK). How can I do that? Thanks

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  • printing using one '\n'

    - by Alex
    I am pretty sure all of you are familiar with the concept of the Big4, and I have several stuffs to do print in each of the constructor, assignment, destructor, and copy constructor. The restriction is this: I CAN'T use more than one newline (e.g., ƒn or std::endl) in any method I can have a method called print, so I am guessing print is where I will put that precious one and only '\n', my problem is that how can the method print which prints different things on each of the element I want to print in each of the Big4? Any idea? Maybe overloading the Big4?

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