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  • Calling inheriting class methods via interface.

    - by Stacey
    Given the scenario... interface IBase{ void Process(int value); } abstract class Base : IBase { public virtual void Process(int value){ throw new NotImplementedException(); } } class Implemented: Base, IBase { public void Process(int value) { // .. some code here.. } } I'm trying to write a loop similar to the following. foreach( Base b in CollectionOfImplemented ) { b.Process( // something will go here // ); } Trying this, it keeps calling Base.Process, instead of Implemented.Process; but the type in the collection is Implemented, not Base. Boxing it seems to work, but I was hoping to see if I could find a more intelligent approach to it, since the Collection will contain other types of objects that also inherit from Base.

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  • Referencing an array to a pointer

    - by james
    I want to refer a pointer to an array by another pointer. Example: void exp() { double var[2]; exp1(&var[0]); printf("\n varvalue is %lf\n",var[0]); } void exp1(double *var) { //updating the value *var[0]=4.0; exp2(&var[0]); } void exp2(double *var) { *var[0]=7.0; } This should update the value as 7.0(the last update).I am getting an array like invalid argument type of unary(*) . How can i correct this?where i am going wrong here?

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  • C++ Declaring an uninitialized variable without a null constructor

    - by xbonez
    Consider the DUPoint class, whose declaration appears below. Assume this code appears in a file named DUPoint.h: #include <string> class DUPoint { public: DUPoint (int x, int y); int getX () const; int getY () const; void setX (int x); void setY (int y); void print(); private: int x_; int y_; }; Is it true that you cannot declare an uninitialized DUPoint variable with a statement such as DUPoint P; using this class as currently configured because it has no null constructor?

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  • Writing a C++ wrapper for a C library

    - by stripes
    I have a legacy C library, written in an OO type form. Typical functions are like: LIB *lib_new(); void lib_free(LIB *lib); int lib_add_option(LIB *lib, int flags); void lib_change_name(LIB *lib, char *name); I'd like to use this library in my C++ program, so I'm thinking a C++ wrapper is required. The above would all seem to map to something like: class LIB { public: LIB(); ~LIB(); int add_option(int flags); void change_name(char *name); ... }; I've never written a C++ wrapper round C before, and can't find much advice about it. Is this a good/typical/sensible approach to creating a C++/C wrapper?

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  • Form Closing help

    - by Michael Quiles
    How can I call the button1_Click event in the form closing event so I don't have to copy and paste the code from button1_Click? public void button1_Click(object sender, EventArgs e) { //Yes or no message box to exit the application DialogResult Response; Response = MessageBox.Show("Are you sure you want to Exit?", "Exit", MessageBoxButtons.YesNo, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2); if (Response == DialogResult.Yes) // Exits the application Application.Exit(); } public void xGameThemeComboBox_SelectedIndexChanged(object sender, EventArgs e) { string folder = Application.StartupPath; string theme = (string)xGameThemeComboBox.Items[xGameThemeComboBox.SelectedIndex]; string path = System.IO.Path.Combine(folder, theme + ".jpg"); Image newImage = new Bitmap(path); if (this.BackgroundImage != null) this.BackgroundImage.Dispose(); { this.BackgroundImage = newImage; } } private void xGameForm_FormClosing(object sender, FormClosingEventArgs e) { // call button1_Click here }

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  • A pointer member variable having different values

    - by Rohan Prabhu
    Ok, to begin with, this is my code: HyperSprite::HyperSprite() { _view = 0; } void HyperSprite::publish(QGraphicsView* view) { _view = view; } void HyperSprite::getKFrame() { if(_view != 0) { qDebug()<<(void*)_view; } } Now, if I call HyperSprite::getKFrame() from within main(), I get the output: 0xbf8ffb84 I have a TCP server, which requires this QGraphicsView* variable. So whenever a new connection is made, HyperSprite::getKFrame() is called. However, whenever I make a connection to my server, this is the output: 0x1e425ff I honestly don't understand this. Shouldn't the value of a member remain same throughout? Why is the pointer value changing? As is obvious, whenever I try to use the _view pointer to access any of its members, a Segmentation Fault occurs. I tried using QSharedPointer, but it also results in the same problem. The data of the QSharedPointer automatically changes. Why is this happening?

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  • Android SurfaceView/Canvas flickering after trying to clear it

    - by Mark D
    So I am trying to clear the Canvas using canvas.drawColor(Color.BLACK) but if I just call this once, the display flickers and displays the old drawing which should have been covered up by the drawColor. Here is the important bits of my code - public void update() { //This method is called by a Thread Canvas canvas = holder.lockCanvas(null); if (canvas != null) { onDraw(canvas); } holder.unlockCanvasAndPost(canvas); } @Override protected void onDraw(Canvas canvas) { if (toClear) { canvas.drawColor(Color.BLACK); //if this is not set to change back to false, it does not flicker toClear = false; } //Draw some objects that are moving around } public void clearScreen() { //This method is called when the user pressed a button toClear = true; } After Googling around a litte, I heard about double buffering but came to the understanding that lockCanvas() and unlockCanvasAndPost() should handle this for me. What is going wrong here?

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  • Why does the compiler give an ambiguous invocation error when passing inherited types?

    - by Matt Mitchell
    What is happening in the C# compiler to cause the following ambiguous invocation compilation error? The same issue applies to extension methods, or when TestClass is generic and using instance rather than static methods. class Type1 { } class Type2 : Type1 {} class TestClass { public static void Do<T>(T something, object o) where T : Type1 {} public static void Do(Type1 something, string o) {} } void Main() { var firstInstance = new Type1(); TestClass.Do(firstInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(firstInstance, "Test"); // Calls Do<T>(T, string) var secondInstance = new Type2(); TestClass.Do(secondInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(secondInstance, "Test"); // "The call is ambiguous" compile error }

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  • Macros giving problems with dladdr()

    - by Veger
    I have implemented tracing behavior using the -finstrument-functions option of gcc and this (simplified) code: void __cyg_profile_func_enter(void *this_fn, void *call_site) { Dl_info di; if(dladdr(this_fn, &di)) printf("entered %s\n", (di.dli_sname?di_dli_sname:"<unknown>")); } This works great, except for one thing: macros are processed as well, but the function prints the information of the function which contains the macro. So functions containing macros have their information printed multiple times (which is of course undesired). Is there anything to detect that a macro is being processed? Or is is possible to turn off instrumenting macros at all? PS Same problems occur with sizeof()

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  • c# event and delegate question

    - by user359562
    I want to detach the custom event but could not detach. Please find below I am using -= to detach the event. I assume after this, TextChanged2 method should not be invoked as I have unregistered the event. Let me know if my understanding is wrong. public delegate void TextChangedEventHandler1(object sender, TextBoxargs ta); public event TextChangedEventHandler1 TextChanged1; private void textBox1_TextChanged(object sender, EventArgs e) { this.TextChanged1 -= new TextChangedEventHandler1(TextChanged2); TextChanged2(sender, e); } public void TextChanged2(object sender, EventArgs e) { textBox1.Text = textBox1.Text.ToUpper(); }

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  • How to simulate Func<T1, T2, TResult> in C++?

    - by Zach
    Hello all, In C#, I use Func to replace Factories. For example: class SqlDataFetcher { public Func<IConnection> CreateConnectionFunc; public void DoRead() { IConnection conn = CreateConnectionFunc(); // call the Func to retrieve a connection } } class Program { public void CreateConnection() { return new SqlConnection(); } public void Main() { SqlDataFetcher f = new SqlDataFetcher(); f.CreateConnectionFunc = this.CreateConnection; ... } } How can I simulate the code above in C++?

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  • How to overwrite virtual fnc in good style? [C++]

    - by atch
    Hi, guys I know this question is very basic but I've met in few publications (websites, books) different style of overwriting virtual function. What I mean is: if I have base class: class Base { public: virtual void f() = 0; }; in some publications I saw that to overwrite this some authors would just say: void f(); and some would still repeat the virtual keyword before void. Which form of overwriting is in good style? Thank you for your answers.

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  • Problem with "not declared in this scope" error

    - by lego69
    I've got: error a1 was not declared in this scope Can somebody please explain why this code causes that? quiz.h #ifndef QUIZ_H_ #define QUIZ_H_ #include "quiz.cpp" class A { private: int player; public: A(int initPlayer); ~A(); void foo(); }; #endif /* QUIZ_H_ */ quiz.cpp #include "quiz.h" #include <iostream> using std::cout; using std::endl; A::A(int initPlayer = 0){ player = initPlayer; } A::~A(){ } void A::foo(){ cout << player; } main function #include "quiz.h" int main() { quiz(7); return 0; } quiz function #include "quiz.h" void quiz(int i) { A a1(i); a1.foo(); }

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  • Define pointcut to capture an interface but not parent or sub interfaces

    - by mR_fr0g
    I was wondering how to define a pointcut in aspecJ the captures any method of an interface but not the methods of any parent or sub interface. pubic interface A { void methodA(); } pubic interface B extends A { void methodB(); } pubic interface C extends B { void methodC(); } I would like a poincut that only catches methodB() and not methodA() or methodC(). Is there any way i can do this in a general way without listing all the sub and super interfaces in the pointcut?

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  • C Struct as an argument

    - by Brian
    I'm wondering what's the difference between sample1 and sample2. Why sometimes I have to pass the struct as an argument and sometimes I can do it without passing it in the function? and how would it be if samplex function needs several structs to work with? would you pass several structs as an argument? struct x { int a; int b; char *c; }; void sample1(struct x **z;){ printf(" first member is %d \n", z[0]->a); } void sample2(){ struct x **z; printf(" first member is %d \n", z[0]->a); // seg fault } int main(void) { struct x **z; sample1(z); sample2(); return 0; }

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  • C++ & C#, how to create wrapper dll in C++ for C# to call instance function in C++ dll?

    - by 5YrsLaterDBA
    Received an unmanaged C++ dll with instance functions which need to be called from my C#. need to write a wrapper C++ dll to bridge the C# and original C++ dll as suggested by experts here. it is new to me and want to learn from you. Header file of the original C++ dll likes this: class EXPORT_MACRO NB_DPSM { private: string sFileNameToAnalyze ; public: NB_DPSM(void); ~NB_DPSM(void); void setFileNameToAnalyze(string FileNameToAnalyze) ; int WriteGenbenchData(string& message) ; }; Start from a Class Library project template or CLR Empty Project template? What's the wrapper code should look like? Anywhere has step by step example for this? thanks,

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  • Java : Using parent class method to access child class variable

    - by Jayant
    I have the following scenario : public class A { private int x = 5; public void print() { System.out.println(x); } } public class B extends A { private int x = 10; /*public void print() { System.out.println(x); }*/ public static void main(String[] args) { B b = new B(); b.print(); } } On executing the code, the output is : 5. How to access the child class(B's) variable(x) via the parent class method? Could this be done without overriding the print() method (i.e. uncommenting it in B)? [This is important because on overriding we will have to rewrite the whole code for the print() method again]

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  • Reference and Value confusion

    - by rgamber
    Hi I read this question on Stack overflow, and tried to do an example. I had the below code: public static void main(String[] args){ int i = 5; Integer I = new Integer(5); increasePrimitive(i); increaseObject(I); System.out.println(i); //Prints 5 - correct System.out.println(I); //Still prints 5 System.out.println(increaseObject2(I)); //Still prints 5 } public static void increasePrimitive(int n){ n++; } public static void increaseObject(Integer n){ n++; } public static int increaseObject2(Integer n){ return n++; } Does the increaseObject print 5 because the value of reference is changing inside that function? Am I right? I am confused why the increasedObject2 prints 5 and not 6. Can anyone please explain?

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  • Android TextWatcher for more than one EditText

    - by Creative MITian
    I want to implement the TextWatcher interface for more than one EditText fields. Currently I am using : text1.addTextChangedListener(this); text2.addTextChangedListener(this); then overriding the methods in my Activity: public void afterTextChanged(Editable s) {} public void beforeTextChanged(CharSequence s, int start, int count, int after) {} public void onTextChanged(CharSequence s, int start, int before, int count) { // do some operation on text of text1 field // do some operation on text of text2 field } However this is working fine but I'm looking for other ways so that I can explicitly identify that in which EditText field the SoftKeyboard is currently focused.

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  • AS3 - Can I have access to the object (or function) who call me?

    - by lk
    I've asked this same question with Python. Now I like to know if this can be done in AS3. If I have something like this: package { public class SomeClass { private function A():void { C() } private function B():void { C() } private function C():void { // who is the caller, A or B ??? } public function SomeClass() { A() B() } } } Despite the design or other issues, this is only a question of an inquiring mind. Note: This has to be done without changing C signature Note 2: I like to have an access to an instance of the caller function so I can call that caller function (if I want to)

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  • c++ possible errors

    - by lego69
    hello I've got error a1 was not declared in this scope, can somebody please explain me my fault my header: #ifndef QUIZ_H_ #define QUIZ_H_ #include "quiz.cpp" class A { private: int player; public: A(int initPlayer); ~A(); void foo(); }; #endif /* QUIZ_H_ */ implementation of class functions: #include "quiz.h" #include <iostream> using std::cout; using std::endl; A::A(int initPlayer = 0){ player = initPlayer; } A::~A(){ } void A::foo(){ cout << player; } my main #include "quiz.h" int main() { quiz(7); return 0; } function quiz: #include "quiz.h" void quiz(int i) { A a1(i); a1.foo(); }

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  • How to find distance between two geopoints in c using calculateDistance(const CWaypoint& wp)

    - by Harsha
    void getAllDataByPointer(string *pname,double *platitude, double *plongitude); void getAllDataByReference(string &pname,double &platitude, double &plongitude); double calculateDistance(const CWaypoint& wp); void print(int format); bool less(const CWaypoint& wp_right); CWaypoint add(const CWaypoint& wp_right); These are the functions I am using. I have the values as output but how to call the latitude values of two different cities so that I can use the following formula distance = ERADIUS * (acos(sin(latitude_1)*sin(latitude_2) + cos(latitude_1) * cos(latitude_2)*cos(longitude_2 - longitude_1)));

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  • how to use string in va_start?

    - by Newbie
    for some reason, i cant get this working: void examplefunctionname(string str, ...){ ... va_start(ap, str.c_str()); nor do i get this work: void examplefunctionname(string str, ...){ ... int len = str.length(); char *strlol = new char[len+1]; for(int i = 0; i < len; i++){ strlol[i] = str[i]; } strlol[len] = 0; va_start(ap, strlol); but this does: void examplefunctionname(const char *str, ...){ ... va_start(ap, str); could someone show me how i can use string instead of const char * there? its outputting random numbers when i call examplefunctionname("%d %d %d", 1337, 1337, 1337)

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  • Default http/admin port in dropwizard project

    - by mithrandir
    I have a dropwizard project and I have maintained a config.yml file at the ROOT of the project (basically at the same level as pom.xml). Here I have specified the HTTP port to be used as follows: http: port:9090 adminPort:9091 I have the following code in my TestService.java file public class TestService extends Service<TestConfiguration> { @Override public void initialize(Bootstrap<TestConfiguration> bootstrap) { bootstrap.setName("test"); } @Override public void run(TestConfiguration config, Environment env) throws Exception { // initialize some resources here.. } public static void main(String[] args) throws Exception { new TestService().run(new String[] { "server" }); } } I expect the config.yml file to be used to determine the HTTP port. However the app always seems to start with the default ports 8080 and 8081. Also note that I am running this from eclipse. Any insights as to what am I doing wrong here ?

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  • Computing Form Location with Button

    - by user2934515
    I'm working on a programming assignment, and I'm trying to make this button take the values from two textboxes, and calculate the new location for the form window. I'm having trouble converting the textbox values to type int, and being made usable by the btnCompute_click method. private void btnCompute_Click(object sender, EventArgs e) { int x = Convert.ToInt32(txtXvalue); int y = Convert.ToInt32(txtYvalue); Location = new Point(x,y); } private void xValue_TextChanged(object sender, EventArgs e) { int xValue = Convert.ToInt32(txtXvalue); } private void yValue_TextChanged(object sender, EventArgs e) { int y = Convert.ToInt32(txtYvalue); } I forgot to add some additional info, the acceptable values for x and y must be positive. Would I use an if...else statement to control the acceptable values?

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