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  • How is inheritance implemented at the memory level?

    - by cambr
    Suppose I have class A { public: void print(){cout<<"A"; }}; class B: public A { public: void print(){cout<<"B"; }}; class C: public C { }; How is inheritance implemented at the memory level? Does C copy print() code to itself or does it have a pointer to the it that points somewhere in A part of the code? How does the same thing happen when we override the previous definition, for example in B (at the memory level)?

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  • How to replace an object in an NSMutableArray at a given index with a new object

    - by shakeelw
    Hi guys. I have an NSMutableArray object(retained, synthesized as all) that is initiated just fine and I can easily add objects to it using the 'addObject:' method. But if I want to replace an object at a certain index with a new one in that NSMutableArray, it doesn't work. For example: ClassA.h @interface ClassA : NSObject { NSMutableArray *list; } @property (nonatomic, copy, readwrite) NSMutableArray *list; end ClassA.m import "ClassA.h" @implementation ClassA @synthesize list; (id)init { [super init]; NSMutableArray *localList = [[NSMutableArray alloc] init]; self.list = localList; [localList release]; //Add initial data [list addObject:@"Hello "]; [list addObject:@"World"]; } // Custom set accessor to ensure the new list is mutable (void)setList:(NSMutableArray *)newList { if (list != newList) { [list release]; list = [newList mutableCopy]; } } -(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex { int i = [theIndex intValue]-1; [self.list replaceObjectAtIndex:i withObject:newTitle]; NSLog((NSString *)[self.list objectAtIndex:i]); // gives the correct output } However, the change remains true only inside the method. from any other method, the NSLog((NSString *)[self.list objectAtIndex:i]); gives the same old value. How can I actually get the old object replaced with the new one at a specific index so that the change can be noticed from within any other method as well. I even modified the method like this, but the result is the same: -(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex { int i = [theIndex intValue]-1; NSMutableArray *localList = [[NSMutableArray alloc] init]; localList = [localList mutableCopy]; for(int j = 0; j < [list count]; j++) { if(j == i) { [localList addObject:newTitle]; NSLog(@"j == 1"); NSLog([NSString stringWithFormat:@"%d", j]); } else { [localList addObject:(NSString *)[self.list objectAtIndex:j]]; } } [self.list release]; //self.list = [localList mutableCopy]; [self setList:localList]; [localList release]; } Please help out guys :)

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  • Java Flow Control Problem

    - by Kyle_Solo
    I am programming a simple 2d game engine. I've decided how I'd like the engine to function: it will be composed of objects containing "events" that my main game loop will trigger when appropriate. A little more about the structure: Every GameObject has an updateEvent method. objectList is a list of all the objects that will receive update events. Only objects on this list have their updateEvent method called by the game loop. I’m trying to implement this method in the GameObject class (This specification is what I’d like the method to achieve): /** * This method removes a GameObject from objectList. The GameObject * should immediately stop executing code, that is, absolutely no more * code inside update events will be executed for the removed game object. * If necessary, control should transfer to the game loop. * @param go The GameObject to be removed */ public void remove(GameObject go) So if an object tries to remove itself inside of an update event, control should transfer back to the game engine: public void updateEvent() { //object's update event remove(this); System.out.println("Should never reach here!"); } Here’s what I have so far. It works, but the more I read about using exceptions for flow control the less I like it, so I want to see if there are alternatives. Remove Method public void remove(GameObject go) { //add to removedList //flag as removed //throw an exception if removing self from inside an updateEvent } Game Loop for(GameObject go : objectList) { try { if (!go.removed) { go.updateEvent(); } else { //object is scheduled to be removed, do nothing } } catch(ObjectRemovedException e) { //control has been transferred back to the game loop //no need to do anything here } } // now remove the objects that are in removedList from objectList 2 questions: Am I correct in assuming that the only way to implement the stop-right-away part of the remove method as described above is by throwing a custom exception and catching it in the game loop? (I know, using exceptions for flow control is like goto, which is bad. I just can’t think of another way to do what I want!) For the removal from the list itself, it is possible for one object to remove one that is farther down on the list. Currently I’m checking a removed flag before executing any code, and at the end of each pass removing the objects to avoid concurrent modification. Is there a better, preferably instant/non-polling way to do this?

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  • Visual Studio 2010 debug minidump

    - by Snake
    Hi all, Consider the following code (written with Visual Studio 2010 and .NET 4.0) using System; namespace DumpTester { class Program { static void Main(string[] args) { int test = new Random().Next(); Console.WriteLine(test + new Random().Next()); Test(); } private static void Test() { throw new Exception(); } } } When running outside of Visual Studio you get this nice window of Microsoft Windows 7 that it is looking for a solution. Obviously, since this is my app, there is none. At that point I create a full dump file of my application with for example Process Explorer. I then open that dmp file from its location and try to debug. But whatever I try, it can't find the location of the source symbols. I tried putting the pdb next to the dump but it just doesn't find it. What am I doing wrong?

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  • fetching savedInstanceState values, nullpointerexception

    - by Johan
    @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main2); savedInstanceState.putString("foo", "bar"); } @Override public void onRestoreInstanceState(Bundle savedInstanceState) { super.onRestoreInstanceState(savedInstanceState); String myString = savedInstanceState.getString("foo"); Log.i("debug", "saved data: " + myString); } Im trying to preserve some values in an activity, but i recieve the following error: 06-23 23:09:44.038: E/AndroidRuntime(17584): java.lang.RuntimeException: Unable to start activity ComponentInfo{se.johanberntsson.activitytest/se.johanberntsson.activitytest.TestActivity}: java.lang.NullPointerException What did I miss here? Thanks

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  • How to create this drop down box [migrated]

    - by mystycs
    I am trying to create this dropdown box that slides down and has the bottom image retain as it slides down withc ontent inside it. I have beent rying to find scripts dedicated to this but i cant find any. Maybe someone can give me a headstart or pointer in doing this. Or has a script i can work off of? Here is my objective. To create a slide down menu that slides down and up on click but retains this look to it.

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  • Form graphics not set when form loads

    - by Jimmy
    My form has a group box which contains two overlapping rectangles. The form's other controls are two sets of four numeric up down controls to set the rectangles' colors. (nudF1,2,3 and 4 set the rectangle that's in front, and nudB1,2,3 and 4 set the rectangle that's behind.) Everything works fine, except that the rectangles do not display the colors set in the numeric up downs when the form first loads. The numeric up down controls' ChangeValue events all call the ShowColors() method. The form's Load event calls the csColorsForm_Load() method. Any suggestions? namespace csColors { public partial class csColorsForm : Form { public csColorsForm() { InitializeComponent(); } private void csColorsForm_Load(object sender, EventArgs e) { this.BackColor = System.Drawing.Color.DarkBlue; SetColors(sender, e); } private void SetColors(object sender, EventArgs e) { Control control = (Control)sender; String ctrlName = control.Name; Graphics objGraphics; Rectangle rect1, rect2; int colorBack, colorFore; objGraphics = this.grpColor.CreateGraphics(); // If calling control is not a forecolor control, paint backcolor rectangle if (ctrlName.Substring(0,4)!="nudF") { colorBack = int.Parse(SetColorsB("nudB"), NumberStyles.HexNumber); SolidBrush BrushB = new SolidBrush(Color.FromArgb(colorBack)); rect1 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushB, rect1); } // Always paint forecolor rectangle colorFore = int.Parse(SetColorsB("nudF"), NumberStyles.HexNumber); SolidBrush BrushF = new SolidBrush(Color.FromArgb(colorFore)); rect2 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushF, rect2); objGraphics.Dispose(); } private string SetColorsB(string nam) { string txt=""; for (int n = 1; n <= 4; ++n) { var ud = Controls[nam + n] as NumericUpDown; int hex = (int)ud.Value; txt += hex.ToString("X2"); } return txt; } private void btnClose_Click(object sender, EventArgs e) { this.Close(); } } }

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  • Does template class/function specialization improves compilation/linker speed?

    - by Stormenet
    Suppose the following template class is heavily used in a project with mostly int as typename and linker speed is noticeably slower since the introduction of this class. template <typename T> class MyClass { void Print() { std::cout << m_tValue << std::endl;; } T m_tValue; } Will defining a class specialization benefit compilation speed? eg. void MyClass<int>::Print() { std::cout << m_tValue << std::endl; }

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  • How come Java doesn't accept my LinkedList in a Generic, but accepts its own?

    - by master chief
    For a class assignment, we can't use any of the languages bultin types, so I'm stuck with my own list. Anyway, here's the situation: public class CrazyStructure <T extends Comparable<? super T>> { MyLinkedList<MyTree<T>> trees; //error: type parameter MyTree is not within its bound } However: public class CrazyStructure <T extends Comparable<? super T>> { LinkedList<MyTree<T>> trees; } Works. MyTree impleements the Comparable interface, but MyLinkedList doesn't. However, Java's LinkedList doesn't implement it either, according to this. So what's the problem and how do I fix it? MyLinkedList: public class MyLinkedList<T extends Comparable<? super T>> { private class Node<T> { private Node<T> next; private T data; protected Node(); protected Node(final T value); } Node<T> firstNode; public MyLinkedList(); public MyLinkedList(T value); //calls node1.value.compareTo(node2.value) private int compareElements(final Node<T> node1, final Node<T> node2); public void insert(T value); public void remove(T value); } MyTree: public class LeftistTree<T extends Comparable<? super T>> implements Comparable { private class Node<T> { private Node<T> left, right; private T data; private int dist; protected Node(); protected Node(final T value); } private Node<T> root; public LeftistTree(); public LeftistTree(final T value); public Node getRoot(); //calls node1.value.compareTo(node2.value) private int compareElements(final Node node1, final Node node2); private Node<T> merge(Node node1, Node node2); public void insert(final T value); public T extractMin(); public int compareTo(final Object param); }

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  • Java: Allowing the child thread to kill itself on InterruptedException?

    - by Zombies
    I am using a ThreadPool via ExecutorService. By calling shutDownNow() it interrupts all running threads in the pool. When this happens I want these threads to give up their resources (socket and db connections) and simply die, but without continuing to run anymore logic, eg: inserting anything into the DB. What is the simplest way to achieve this? Bellow is some sample code: public void threadTest() { Thread t = new Thread(new Runnable() { public void run() { try { Thread.sleep(999999); } catch (InterruptedException e) { //invoke thread suicide logic here } } }); t.start(); t.interrupt(); try { Thread.sleep(4000); } catch (InterruptedException e) { } }

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  • Print an EObject ?

    - by tul
    I am writing some eclipse emf code and would like to print the content of an EObject (not store it to disk). Here is what I try: public static void print(EObject obj) { Resource eResource = obj.eResource(); try { eResource.save(System.out, null); } catch (IOException e) { e.printStackTrace(); } } but that gives a NullPointerException. I have tried this instead: public static void print(EObject obj) { ResourceSet resourceSet = new ResourceSetImpl(); resourceSet.getResourceFactoryRegistry().getProtocolToFactoryMap() .put("*", new XMIResourceFactoryImpl()); Resource resource = resourceSet.createResource(URI.createURI("dummyfile.xml")); resource.getContents().add(obj); try { resource.save(System.out, null); } catch (IOException ioe) { ioe.printStackTrace(); } } This works, but is it not possible to print to screen without specifying a dummy URI??

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  • Passing message over network

    - by Sylvestre Equy
    Hi, I'm currently trying to develop a message-oriented networking framework and I'm a bit stuck on the internal mechanism. Here are the problematic interfaces : public interface IMessage { } public class Connection { public void Subscribe<TMessage>(Action<TMessage> messageCallback); public void Send<TMessage>(TMessage message); } The Send method does not seem complicated, though the mechanism behind Subscribe seems a bit more painful. Obviously when receiving a message on one end of the connection, I'll have to invoke the appropriate delegate. Do you have any advice on how to read messages and easily detect their types ? By the way, I'd like to avoid to use MSMQ.

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  • Navigationcontroller, why isnt this working?

    - by f0rz
    Hi ! Why wont this work? View1 loads View2. In view2: - (void) goToView { View3 *plainText = [[Tabview_testViewController alloc] initWithNibName:@"View3" bundle:nil]; [self.navigationController pushViewController:plainText animated: NO]; [plainText release]; } - (void)viewDidLoad { [self goToView]; [super viewDidLoad]; } This will not trigger navigationController to pushView, but if I add a button and setAction (goToView) it works perfectly. What kind of problem do I missing here? Regards

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  • C++: How do I pass a function(without knowing its parameters) to another function?

    - by Ninja
    Hi all. I'm trying to create a function that will store and repeat another function given as a parameter for a specific amount of time or repeats given. But when you want to pass a function as a parameter you have to know all of its parameters before hand. How would I do if I wanted to pass the function as one parameter, and the parameters as another? void AddTimer(float time, int repeats, void (*func), params); // I know params has no type and that (*func) is missing parameters but it is just to show you what I mean Thanks in advance

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  • Problem in creating another thread

    - by Avinash
    Hi, I am using NSThread to create different thread and displaying images in my application on a new thread instead of main thread. On main thread i am working with a table view which is displaying data from XML file, In the same view I am displaying images below. But, displaying images on new thread is not working properly. Did i made any mistake in creating Here below is my code. Please help me its urgent. Thanks in advance...................... - (void)viewDidLoad { [super viewDidLoad]; [NSThread detachNewThreadSelector:@selector(startTheBackgroundJob) toTarget:self withObject:nil]; } - (void)startTheBackgroundJob { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; currentLocationImageView = [[UIImageView alloc] init]; NSArray *images = [NSArray arrayWithObjects:img1, img2, nil]; [currentLocationImageView setAnimationImages:images]; [currentLocationImageView setAnimationRepeatCount:0]; [currentLocationImageView setAnimationDuration:5.0]; [self.view addSubview:currentLocationImageView]; [pool release]; }

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  • Undefined template methods trick ?

    - by Matthieu M.
    A colleague of mine told me about a little piece of design he has used with his team that sent my mind boiling. It's a kind of traits class that they can specialize in an extremely decoupled way. I've had a hard time understanding how it could possibly work, and I am still unsure of the idea I have, so I thought I would ask for help here. We are talking g++ here, specifically the versions 3.4.2 and 4.3.2 (it seems to work with both). The idea is quite simple: 1- Define the interface // interface.h template <class T> struct Interface { void foo(); // the method is not implemented, it could not work if it was }; // // I do not think it is necessary // but they prefer free-standing methods with templates // because of the automatic argument deduction // template <class T> void foo(Interface<T>& interface) { interface.foo(); } 2- Define a class, and in the source file specialize the interface for this class (defining its methods) // special.h class Special {}; // special.cpp #include "interface.h" #include "special.h" // // Note that this specialization is not visible outside of this translation unit // template <> struct Interface<Special> { void foo() { std::cout << "Special" << std::endl; } }; 3- To use, it's simple too: // main.cpp #include "interface.h" class Special; // yes, it only costs a forward declaration // which helps much in term of dependencies int main(int argc, char* argv[]) { Interface<Special> special; foo(special); return 0; }; It's an undefined symbol if no translation unit defined a specialization of Interface for Special. Now, I would have thought this would require the export keyword, which to my knowledge has never been implemented in g++ (and only implemented once in a C++ compiler, with its authors advising anyone not to, given the time and effort it took them). I suspect it's got something to do with the linker resolving the templates methods... Do you have ever met anything like this before ? Does it conform to the standard or do you think it's a fortunate coincidence it works ? I must admit I am quite puzzled by the construct...

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  • C# Closing a form during a constructor

    - by pm_2
    Is it possible to close a form while the constructor is executing (or simply to stop it showing at this stage)? I have the following code: public partial class MyForm : Form { public MyForm() { if (MyFunc()) { this.Close(); } } } Which errors in Main(), here: static void Main() { ... // Following line errors Application.Run(new MyForm()); } I’ve tried checking the result of MyForm like this: static void Main() { ... MyForm frm = new MyForm(); if (frm != null) { // Following line errors Application.Run(frm); } } But that doesn’t seem to help. Can anyone tell me a way around this, please? Maybe a way to check the form to see if it still exists?

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  • Make sure base method gets called in C#

    - by Fnatte
    Can I somehow force a derived class to always call the overridden methods base? public class BaseClass { public virtual void Update() { if(condition) { throw new Exception("..."); // Prevent derived method to be called } } } And then in a derived class : public override void Update() { base.Update(); // Forced call // Do any work } I've searched and found a suggestion to use a non-virtual Update() but also a protected virtual UpdateEx(). It just doesn't feel very neat, isn't there any better way? I hope you get the question and I am sorry for any bad English.

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  • How do I do a game loop in c99?

    - by linitbuff
    I'm having trouble with how to structure a game using c99. I've seen a few tutorials on making a game loop, but they are all done with c++ and classes. My main problem seems to be moving data around between the functions without creating a mess, and what stuff to put in what header files etc. Do I just do something similar to the c++ loops, and create a class-like header with a structure containing all items needed by more than one of the functions, along with the prototypes of said functions, and include the header in each function's header file? Then, in the main function, instantiate the structure and pass a pointer to it to every function in the loop? Is this ok, or is there a better way to do it, and are there any good 'c' specific tutorials available? Cheers

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  • Extend base class properties

    - by user1888033
    I need your help to extend my base class, here is the similar structure i have. public class ShowRoomA { public audi AudiModelA { get; set; } public benz benzModelA { get; set; } } public class audi { public string Name { get; set; } public string AC { get; set; } public string PowerStearing { get; set; } } public class benz { public string Name { get; set; } public string AC { get; set; } public string AirBag { get; set; } public string MusicSystem { get; set; } } //My Implementation class like this class Main() { private void UpdateDetails() { ShowRoomA ojbMahi = new ShowRoomA(); GetDetails( ojbMahi ); // this works fine } private void GetDetails(ShowRoomA objShowRoom) { objShowRoom = new objShowRoom(); objShowRoom.audi = new audi(); objShowRoom.audi.Name = "AUDIMODEL94CD698"; objShowRoom.audi.AC = "6 TON"; objShowRoom.audi.PowerStearing = "Electric"; objShowRoom.benz= new benz(); objShowRoom.audi.Name = "BENZMODEL34LCX"; objShowRoom.audi.AC = "8 TON"; objShowRoom.audi.AirBag = "Two (1+1)"; objShowRoom.audi.MusicSystem = "Poineer 3500W"; } } // Till this cool. // Now I got requirement for ShowRoomB with replacement of old audi and benz with new models and new other brand cars also added. // I don't want to modify GetDetails() method. by reusing this method additional logic i want to apply to my new extended model. // Here I struck in designing my new model of ShowRoomB (base of ShowRoomA) ... I have tried some thing like... but not sure. public class audiModelB:audi { public string JetEngine { get; set; } } public class benzModelB:benz { public string JetEngine { get; set; } } public class ShowRoomB { public audiModelB AudiModelB { get; set; } public benzModelB benzModelB { get; set; } } // My new code to Implementation class like this class Main() { private void UpdateDetails() { ShowRoomB ojbNahi = new ShowRoomB(); GetDetails( ojbNahi ); // this is NOT working! I know this object does not contain base class directly, still some what i want fill my new model with old properties. Kindly suggest here } } Can any one please give me solutions how to achieve my extending requirement for base class "ShowroomA" Really appreciated your time and suggestions. Thanks in advance,

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  • Check if a type is an instantiation of a template

    - by Pedro Lacerda
    I have structs like struct RGBA (T) {/* ... */} struct BMPFile (DataT) if (is(DataT == RGBA)) {/* ... */} But is(DataT == RGBA) cannot work because DataT is a type and RGBA is a template. Instead I need check if a type is an instantiation of a template in order to declare file like BMPFile!(RGBA!ushort) file; In a comment @FeepingCreature showed struct RGBA(T) { alias void isRGBAStruct; } struct BMPFile (DataT) if (is(DataT.isRGBAStruct)) {} Although to be working I have no tips on alias void isRGBAStruct.

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  • How to keep a .NET console app running?

    - by intoorbit
    Consider a Console application that starts up some services in a separate thread. All it needs to do is wait for the user to press Ctrl+C to shut it down. Which of the following is the better way to do this? static ManualResetEvent _quitEvent = new ManualResetEvent(false); static void Main() { Console.CancelKeyPress += delegate { _quitEvent.Set(); }; // kick off asynchronous stuff _quitEvent.WaitOne(); // cleanup/shutdown and quit } Or this, using Thread.Sleep(1): static bool _quitFlag = false; static void Main() { Console.CancelKeyPress += delegate { _quitFlag = true; }; // kick off asynchronous stuff while (!_quitFlag) { Thread.Sleep(1); } // cleanup/shutdown and quit }

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  • error in copy/ paste of image

    - by sayyad
    I am getting an error by implementing this simple code. I donot understand where I am doing mistake. // ERROR An unhandled exception of type 'System.NullReferenceException' occurred in ImageCSharp.exe Additional information: Der Objektverweis wurde nicht auf eine Objektinstanz festgelegt. I can get clipboard text but why i can't get /set image. //CODE public void copy() { // Determine the active child form. fImage activeChild = this.ActiveMdiChild as fImage; if (activeChild != null) { PictureBox mypicbox = activeChild.picbox; string win_name = activeChild.Tag.ToString(); Clipboard.SetImage(mypicbox.Image); Clipboard.SetText(win_name); } } private void paste() { Image im= Clipboard.GetImage(); this.pictureBox1.Image = im; MessageBox.Show(im.Size.ToString()); } regards,

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  • Purpose of IF, ELSE, FOR macros ?

    - by psihodelia
    I have a source code of a library which has a lot of strange IF, ELSE, FOR, etc. macros for all common C-keywords instead of using just usual if,else,for,while keywords. These macros are defined like this: #define IF( a) if( increment_if(), a) where increment_if() function is defined so: static __inline void increment_if( void) { // If the "IF" operator comes just after an "ELSE", its counter // must not be incremented. ... //implementation } I don't really understand, what is the purpose of such macros? This library is for a real-time application and I suppose that using such macros must slow-down an application.

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