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  • Flex Tree Properties, Null Reference?

    - by mvrak
    I am pulling down a large XML file and I have no control over it's structure. I used a custom function to use the tag name to view the tree structure as a flex tree, but then it breaks. I am guessing it has something to do with my other function, one that calls attribute values from the selected node. See code. <mx:Tree x="254" y="21" width="498" height="579" id="xmllisttree" labelFunction="namer" dataProvider="{treeData}" showRoot="false" change="treeChanged(event)" /> //and the Cdata import mx.rpc.events.ResultEvent; [Bindable] private var fullXML:XMLList; private function contentHandler(evt:ResultEvent):void{ fullXML = evt.result.page; } [Bindable] public var selectedNode:Object; public function treeChanged(event:Event):void { selectedNode=Tree(event.target).selectedItem; } public function namer(item:Object):String { var node:XML = XML(item); var nodeName:QName = node.name(); var stringtest:String ="bunny"; return nodeName.localName; } The error is TypeError: Error #1009: Cannot access a property or method of a null object reference. Where is the null reference?

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  • Eror while showing returned value on parent window from chield (Dialog box) window using JSF Trinida

    - by Navnath
    Hi There, I am using Myfaces and Trinidad tld's for page design. In that, I am trying to implement Dialog box which will going to open on button click with tacking some value from parent window and return result to Parent window. Now the problem is I can send value to Dialog box and also get return from dialog box successfully, but there is problem to show return value on Parent window because parent window is not reflecting that value and ask for refresh page. When I refresh page, it again open the pop up, i.e. it resending the previous request. Here is my return code. private UIXInput input; public UIXInput getInput() { return input; } public void setInput(UIXInput input) { this.input = input; } public void returned(ReturnEvent event) { if (event.getReturnValue() != null) { getInput().setValue(event.getReturnValue()); RequestContext afContext = RequestContext.getCurrentInstance(); afContext.addPartialTarget(getInput()); } } Next is I have bind input variable with field which need to reflect return value. Here is .jspx code. I have download Trinidad dialog code and try to run on local system, but it not showing any dialog box. But once I remove partialSubmit="true" attribute from comment button which shows dialog box, Then I can see dialog box. Is this attribute making an above error? I hope I have explain my problem clearly. Please...Please let me know any any kind of solution, suggestion. I have spend almost a week to resolve this issue, but.......didn't succeed. Thank You in advance, Navnath Kumbhar.

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  • Detect Application Shutdown in C# NET?

    - by Michael Pfiffer
    I am writing a small console application (will be ran as a service) that basically starts a Java app when it is running, shuts itself down if the Java app closes, and shuts down the Java app if it closes. I think I have the first two working properly, but I don't know how to detect when the .NET application is shutting down so that I can shutdown the Java app prior to that happening. Google search just returns a bunch of stuff about detecting Windows shutting down. Can anyone tell me how I can handle that part and if the rest looks fine? namespace MinecraftDaemon { class Program { public static void LaunchMinecraft(String file, String memoryValue) { String memParams = "-Xmx" + memoryValue + "M" + " -Xms" + memoryValue + "M "; String args = memParams + "-jar " + file + " nogui"; ProcessStartInfo processInfo = new ProcessStartInfo("java.exe", args); processInfo.CreateNoWindow = true; processInfo.UseShellExecute = false; try { using (Process minecraftProcess = Process.Start(processInfo)) { minecraftProcess.WaitForExit(); } } catch { // Log Error } } static void Main(string[] args) { Arguments CommandLine = new Arguments(args); if (CommandLine["file"] != null && CommandLine["memory"] != null) { // Launch the Application LaunchMinecraft(CommandLine["file"], CommandLine["memory"]); } else { LaunchMinecraft("minecraft_server.jar", "1024"); } } } }

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  • Restore and preserve UIViewController pushed from UINavigationController, no storyboard

    - by user2908112
    I try to restore a simple UIViewController that I pushed from my initial view controller. The first one is preserved, but the second one just disappear when relaunched. I don't use storyboard. I implement the protocol in every view controller and add the restorationIdentifier and restorationClass to each one of them. The second viewController inherit from a third viewController and is initialized from a xib file. I'm not sure if I need to implement the UIViewControllerRestoration to this third since I don't use it directly. My code looks like typically like this: - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { // Custom initialization self.restorationIdentifier = @"EditNotificationViewController"; self.restorationClass = [self class]; } return self; } -(void)encodeRestorableStateWithCoder:(NSCoder *)coder { } -(void)decodeRestorableStateWithCoder:(NSCoder *)coder { } +(UIViewController *)viewControllerWithRestorationIdentifierPath:(NSArray *)identifierComponents coder:(NSCoder *)coder { EditNotificationViewController* envc = [[EditNotificationViewController alloc] initWithNibName:@"SearchFormViewController" bundle:nil]; return envc; } Should perhaps the navigationController be subclassed so it too can inherit from UIViewControllerRestoration?

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  • Need advice on C++ coding pattern

    - by Kotti
    Hi! I have a working prototype of a game engine and right now I'm doing some refactoring. What I'm asking for is your opinion on usage of the following C++ coding patterns. I have implemented some trivial algorithms for collision detection and they are implemented the following way: Not shown here - class constructor is made private and using algorithms looks like Algorithm::HandleInnerCollision(...) struct Algorithm { // Private routines static bool is_inside(Point& p, Object& object) { // (...) } public: /** * Handle collision where the moving object should be always * located inside the static object * * @param MovingObject & mobject * @param const StaticObject & sobject * @return void * @see */ static void HandleInnerCollision(MovingObject& mobject, const StaticObject& sobject) { // (...) } So, my question is - somebody advised me to do it "the C++" way - so that all functions are wrapped in a namespace, but not in a class. Is there some good way to preserve privating if I will wrap them into a namespace as adviced? What I want to have is a simple interface and ability to call functions as Algorithm::HandleInnerCollision(...) while not polluting the namespace with other functions such as is_inside(...) Of, if you can advise any alternative design pattern for such kind of logics, I would really appreciate that...

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  • Completed Event not triggering for web service on some systems

    - by Farukh
    Hi, This is rather weird issue that I am facing with by WCF/Silverlight application. I am using a WCF to get data from a database for my Silverlight application and the completed event is not triggering for method in WCF on some systems. I have checked the called method executes properly has returns the values. I have checked via Fiddler and it clearly shows that response has the returned values as well. However the completed event is not getting triggered. Moreover in few of the systems, everything is fine and I am able to process the returned value in the completed method. Any thoughts or suggestions would be greatly appreciated. I have tried searching around the web but without any luck :( Following is the code.. Calling the method.. void RFCDeploy_Loaded(object sender, RoutedEventArgs e) { btnSelectFile.IsEnabled = true; btnUploadFile.IsEnabled = false; btnSelectFile.Click += new RoutedEventHandler(btnSelectFile_Click); btnUploadFile.Click += new RoutedEventHandler(btnUploadFile_Click); RFCChangeDataGrid.KeyDown += new KeyEventHandler(RFCChangeDataGrid_KeyDown); btnAddRFCManually.Click += new RoutedEventHandler(btnAddRFCManually_Click); ServiceReference1.DataService1Client ws = new BEVDashBoard.ServiceReference1.DataService1Client(); ws.GetRFCChangeCompleted += new EventHandler<BEVDashBoard.ServiceReference1.GetRFCChangeCompletedEventArgs>(ws_GetRFCChangeCompleted); ws.GetRFCChangeAsync(); this.BusyIndicator1.IsBusy = true; } Completed Event.... void ws_GetRFCChangeCompleted(object sender, BEVDashBoard.ServiceReference1.GetRFCChangeCompletedEventArgs e) { PagedCollectionView view = new PagedCollectionView(e.Result); view.GroupDescriptions.Add(new PropertyGroupDescription("RFC")); RFCChangeDataGrid.ItemsSource = view; foreach (CollectionViewGroup group in view.Groups) { RFCChangeDataGrid.CollapseRowGroup(group, true); } this.BusyIndicator1.IsBusy = false; } Please note that this WCF has lots of other method as well and all of them are working fine.... I have problem with only this method... Thanks...

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  • how to write binary copy of structure array to file

    - by cerr
    I would like to write a binary image of a structure array to a binary file. I have tried this so far: #include <stdio.h> #include <string.h> #define NUM 256 const char *fname="binary.bin"; typedef struct foo_s { int intA; int intB; char string[20]; }foo_t; void main (void) { foo_t bar[NUM]; bar[0].intA = 10; bar[0].intB = 999; strcpy(bar[0].string,"Hello World!"); Save(bar); printf("%s written succesfully!\n",fname); } int Save(foo_t* pData) { FILE *pFile; int ptr = 0; int itr = 0; pFile = fopen(fname, "w"); if (pFile == NULL) { printf("couldn't open %s\n", fname); return; } for (itr = 0; itr<NUM; itr++) { for (ptr=0; ptr<sizeof(foo_t); ptr++) { fputc((unsigned char)*((&pData[itr])+ptr), pFile); } fclose(pFile); } } but the compiler is saying aggregate value used where an integer was expected fputc((unsigned char)*((&pData[itr])+ptr), pFile); and I don't quite understand why, what am I doing wrong? Thanks!

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  • JLabel wont change color twice

    - by Aly
    Hi, I have the following code: public class Test extends JFrame implements ActionListener{ private static final Color TRANSP_WHITE = new Color(new Float(1), new Float(1), new Float(1), new Float(0.5)); private static final Color TRANSP_RED = new Color(new Float(1), new Float(0), new Float(0), new Float(0.1)); private static final Color[] COLORS = new Color[]{ TRANSP_RED, TRANSP_WHITE}; private int index = 0; private JLabel label; private JButton button; public Test(){ super(); setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS)); label = new JLabel("hello world"); label.setOpaque(true); label.setBackground(TRANSP_WHITE); getContentPane().add(label); button = new JButton("Click Me"); button.addActionListener(this); getContentPane().add(button); pack(); setVisible(true); } @Override public void actionPerformed(ActionEvent e) { if(e.getSource().equals(button)){ label.setBackground(COLORS[index % (COLORS.length - 1)]); } } public static void main(String[] args) { new Test(); } } When I run it I get the label with the TRANSP_WHITE background and then when I click the button this color changes to TRANSP_RED but when I click it again I see no change in color. Does anyone know why? Thanks

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  • How do I post back information from a webpage that has post-generated content?

    - by meanbunny
    Ok so I am very new to html and the web. Right now I am trying to generate list items on the fly and then have them post back to the web server so I know what the person is trying to obtain. Here is the code for generating the list items: foreach (var item in dataList) { MyDataList.InnerHtml += "<li><a runat='server' onclick='li_Click' id='" + item.Name + "-button'></a></li>"; } Further down I have my click event. protected void li_Click(object sender, EventArgs e) { //How do I determine here which item was actually clicked? } My question is how do I determine which list item was clicked? Btw, the code running behind is C#. EDIT 1 LinkButton link = new LinkButton(); link.ID = "all-button"; link.Text = "All"; link.Click += new EventHandler(link_Click); MyDataList.Controls.Add(link); Then below I have my link_Click event that never seems to hit a breakpoint. void link_Click(object sender, EventArgs e) { if (sender != null) { if (sender.GetType() == typeof(LinkButton)) { LinkButton button = (LinkButton)sender; if (button.ID == "all-button") { } } } } I know this has to be possible I just cant figure out what I am missing. Edit 2 Ok ok I think I know what the problem is. I was trying to add a second list inside of another list. This was causing the whole thing to have problems. It is working now.

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  • iPhone and iPad : Doing a "select * from something" query in a SQLite database

    - by Abramodj
    Hi folks, i'm trying to use the SQLite data base in my iPad app, and here's my function to make a query: - (void)executeQuery:(char*)query { NSString *file = [self getWritableDBPath]; NSFileManager *fileManager = [NSFileManager defaultManager]; BOOL success = [fileManager fileExistsAtPath:file]; // If its not a local copy set it to the bundle copy if(!success) { //file = [[NSBundle mainBundle] pathForResource:DATABASE_TITLE ofType:@"db"]; [self createEditableCopyOfDatabaseIfNeeded]; } dataArray = NULL; dataArray = [NSMutableArray array]; sqlite3 *database = NULL; if (sqlite3_open([file UTF8String], &database) == SQLITE_OK) { sqlite3_exec(database, query, loadTimesCallback, dataArray, NULL); } sqlite3_close(database); [self logResults]; } if I call [self executeQuery:"select name from table1"]; everything is working fine. But if i call [self executeQuery:"select * from cars"]; the app crashes telling me that the NSMutableArray dataArray is not the right kind of variable where to set the query results. So, how can i do a "select * form table1" query, and store the results? Thanks! EDIT: Here's my loadTimesCallback method: static int loadTimesCallback(void *context, int count, char **values, char **columns) { NSMutableArray *times = (NSMutableArray *)context; for (int i=0; i < count; i++) { const char *nameCString = values[i]; [times addObject:[NSString stringWithUTF8String:nameCString]]; } return SQLITE_OK; }

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  • Creating a C++ DLL and then using it in C#

    - by Major
    Ok I'm trying to make a C++ DLL that I can then call and reference in a c# App. I've already made a simple dll using the numberous guides out there, however when I try to reference it in the C# app I get the error Unable to load DLL 'SDES.dll': The specified module could not be found. The code for the program is as follows (bear with me I'm going to include all the files) //These are the DLL Files. ifndef TestDLL_H define TestDLL_H extern "C" { // Returns a + b __declspec(dllexport) double Add(double a, double b); // Returns a - b __declspec(dllexport) double Subtract(double a, double b); // Returns a * b __declspec(dllexport) double Multiply(double a, double b); // Returns a / b // Throws DivideByZeroException if b is 0 __declspec(dllexport) double Divide(double a, double b); } endif //.cpp include "test.h" include using namespace std; extern double __cdecl Add(double a, double b) { return a + b; } extern double __cdecl Subtract(double a, double b) { return a - b; } extern double __cdecl Multiply(double a, double b) { return a * b; } extern double __cdecl Divide(double a, double b) { if (b == 0) { throw new invalid_argument("b cannot be zero!"); } return a / b; } //C# Program using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; namespace ConsoleApplication1 { class Program { [DllImport("SDES.dll")] public static extern void SimulateGameDLL(int a, int b); static void Main(string[] args) { SimulateGameDLL(1, 2); //Error here... } } } Anyone have any idea's what I may be missing in my program? Let me know if I missed some code or if you have any questions.

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  • Using an empty column as a divider in a JTable.

    - by Catalina Island
    I'm trying to use an empty column as a divider between pairs of columns in a JTable. Here's a picture and code for what I have so far. I know I can change the look using a custom TableCellRenderer. Before I go down that road, is there a better way to do this? Any ideas appreciated. import javax.swing.*; import javax.swing.table.*; public class TablePanel extends JPanel { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { JFrame f = new JFrame("TablePanel"); f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); f.add(new TablePanel()); f.pack(); f.setVisible(true); } }); } public TablePanel() { TableModel dataModel = new MyModel(); JTable table = new JTable(dataModel); table.getColumnModel().getColumn(MyModel.DIVIDER).setMaxWidth(0); JScrollPane jsp = new JScrollPane(table); jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); this.add(jsp); } private static class MyModel extends AbstractTableModel { private static final int DIVIDER = 2; private final String[] names = { "A1", "A2", "", "B1", "B2" }; @Override public int getRowCount() { return 32; } @Override public int getColumnCount() { return names.length; } @Override public String getColumnName(int col) { if (col == DIVIDER) return ""; return names[col]; } @Override public Object getValueAt(int row, int col) { if (col == DIVIDER) return ""; return (row + 1) / 10.0; } @Override public Class<?> getColumnClass(int col) { if (col == DIVIDER) return String.class; return Number.class; } } }

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  • Binding a value to one of two possibilities in Guice

    - by Kelvin Chung
    Suppose I have a value for which I have a default, which can be overridden if System.getProperty("foo") is set. I have one module for which I have bindConstant().annotatedWith(Names.named("Default foo")).to(defaultValue); I'm wondering what the best way of implementing a module for which I want to bind something annotated with "foo" to System.getProperty("foo"), or, if it does not exist, the "Default foo" binding. I've thought of a simple module like so: public class SimpleIfBlockModule extends AbstractModule { @Override public void configure() { requireBinding(Key.get(String.class, Names.named("Default foo"))); if (System.getProperties().containsKey("foo")) { bindConstant().annotatedWith(Names.named("foo")).to(System.getProperty("foo")); } else { bind(String.class).annotatedWith(Names.named("foo")).to(Key.get(String.class, Names.named("Default foo"))); } } } I've also considered creating a "system property module" like so: public class SystemPropertyModule extends PrivateModule { @Override public void configure() { Names.bindProperties(binder(), System.getProperties()); if (System.getProperties().contains("foo")) { expose(String.class).annotatedWith(Names.named("foo")); } } } And using SystemPropertyModule to create an injector that a third module, which does the binding of "foo". Both of these seem to have their downsides, so I'm wondering if there is anything I should be doing differently. I was hoping for something that's both injector-free and reasonably generalizable to multiple "foo" attributes. Any ideas?

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  • how to emulate thread local storage at user space in C++ ?

    - by vprajan
    I am working on a mobile platform over Nucleus RTOS. It uses Nucleus Threading system but it doesn't have support for explicit thread local storage i.e, TlsAlloc, TlsSetValue, TlsGetValue, TlsFree APIs. The platform doesn't have user space pthreads as well. I found that __thread storage modifier is present in most of the C++ compilers. But i don't know how to make it work for my kind of usage. How does __thread keyword can be mapped with explicit thread local storage? I read many articles but nothing is so clear for giving me the following basic information will __thread variable different for each thread ? How to write to that and read from it ? does each thread has exactly one copy of the variable ? following is the pthread based implementation: pthread_key_t m_key; struct Data : Noncopyable { Data(T* value, void* owner) : value(value), owner(owner) {} int* value; }; inline ThreadSpecific() { int error = pthread_key_create(&m_key, destroy); if (error) CRASH(); } inline ~ThreadSpecific() { pthread_key_delete(m_key); // Does not invoke destructor functions. } inline T* get() { Data* data = static_cast<Data*>(pthread_getspecific(m_key)); return data ? data->value : 0; } inline void set(T* ptr) { ASSERT(!get()); pthread_setspecific(m_key, new Data(ptr, this)); } How to make the above code use __thread way to set & get specific value ? where/when does the create & delete happen? If this is not possible, how to write custom pthread_setspecific, pthread_getspecific kind of APIs. I tried using a C++ global map and index it uniquely for each thread and retrieved data from it. But it didn't work well.

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  • NSMutableArray for Object which has NSString property causes memory leak

    - by user262325
    Hello everyone I hope to add objects to a NSMutableArray "myArray", The NSMutableArray is the array for FileObj which has a NSString property "fileName" #import <UIKit/UIKit.h> @interface FileObj : NSObject { NSString *fileName; } -(void) setfileName:(NSString *)s ; -(NSString *) getfileName ; @end // // File.m// #import "File.h" @implementation FileObj -(void) setfileName:(NSString *)s ; { fileName=s; } -(NSString *) getfileName ; { return fileName; } @end I initialize the myArray here: NSMutableArray *temarray; temarray=[[NSMutableArray alloc] init]; self.myArray=temarray; [temarray release]; the codes to add object to myArray FileObj *newobj=[[FileObj alloc]init ]; NSString *fieldValue2 = [[NSString alloc] initWithUTF8String:@"aaaa"]; [newobj setfileName:fieldValue2]; [myArray addObject:newobj]; [fieldValue2 release]; //**if I enabled the line, it will cause crash** //**if I disable the line, it will cause memory leak** [newobj release]; Welcome any comment Thanks interdev

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  • Get type of the parameter from list of objects, templates, C++

    - by CrocodileDundee
    This question follows to my previous question Get type of the parameter, templates, C++ There is the following data structure: Object1.h template <class T> class Object1 { private: T a1; T a2; public: T getA1() {return a1;} typedef T type; }; Object2.h template <class T> class Object2: public Object1 <T> { private: T b1; T b2; public: T getB1() {return b1;} } List.h template <typename Item> struct TList { typedef std::vector <Item> Type; }; template <typename Item> class List { private: typename TList <Item>::Type items; }; Is there any way how to get type T of an object from the list of objects (i.e. Object is not a direct parameter of the function but a template parameter)? template <class Object> void process (List <Object> *objects) { typename Object::type a1 = objects[0].getA1(); // g++ error: 'Object1<double>*' is not a class, struct, or union type } But his construction works (i.e. Object represents a parameter of the function) template <class Object> void process (Object *o1) { typename Object::type a1 = o1.getA1(); // OK }

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  • Problems with starting an activity in onStart

    - by Fizz
    Hello everyone. I'm trying to start a floating activity from onStart to retrieve some info from the user right when the initial activity begins. I have the following: @Override public void onStart(){ super.onStart(); callProfileDialog(); } And callProfileDialog() is just: private void callProfileDialog(){ Intent i = new Intent(this, com.utility.ProfileDialog.class); startActivityForResult(i, PROFDIALOG); } ProfileDialog.class returns a String from an input box. If the result returned is RESULT_CANCELED then I restart the activity. The problem I'm having is that when the program starts, the screen is just black. If I hit the Back button a RESULT_CANCELED is returned then the initial activity shows as well as the floating activity (since it recalled itself when it got a RESULT_CANCELED). Why can't I get the activities show by calling ProfileDialog.class from onStart()? I got the same result when I called it at the end of onCreate() which is way I switch over to use onStart(). Thanks for the help.

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  • calling a function from a set of overloads depending on the dynamic type of an object

    - by Jasper
    I feel like the answer to this question is really simple, but I really am having trouble finding it. So here goes: Suppose you have the following classes: class Base; class Child : public Base; class Displayer { public: Displayer(Base* element); Displayer(Child* element); } Additionally, I have a Base* object which might point to either an instance of the class Base or an instance of the class Child. Now I want to create a Displayer based on the element pointed to by object, however, I want to pick the right version of the constructor. As I currently have it, this would accomplish just that (I am being a bit fuzzy with my C++ here, but I think this the clearest way) object->createDisplayer(); virtual void Base::createDisplayer() { new Displayer(this); } virtual void Child::createDisplayer() { new Displayer(this); } This works, however, there is a problem with this: Base and Child are part of the application system, while Displayer is part of the GUI system. I want to build the GUI system independently of the Application system, so that it is easy to replace the GUI. This means that Base and Child should not know about Displayer. However, I do not know how I can achieve this without letting the Application classes know about the GUI. Am I missing something very obvious or am I trying something that is not possible?

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  • how to POST two strings?

    - by Garrith
    Im trying to create a POST method for my AddTagtoGroup which looks like this (altho still confused as string group never seems to be used): List<Group> Groups = new List<Group>(); List<Tag> tags = new List<Tag>(); public void AddTagtoGroup(string group, string tag) { var result = Groups.Where(n => String.Equals(n.GroupName, tag)).FirstOrDefault(); if (result != null) { result.Tags.Add(new Tag() { TagName = tag }); } } My data contracts looks like this: [DataContract(Name = "Group")] public class Group { public Group() // not sure if this has to have a datamember { Tags = new List<Tag>(); } [DataMember(Name = "GroupName")] public string GroupName { get; set; } public List<Tag> Tags { get; set; } // datamember or not? } [DataContract(Name = "Tag")] public class Tag { [DataMember(Name = "TagName")] public string TagName { get; set; } } And my post method looks like this but im unsure what to put in the uri template? [OperationContract] [WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Bare, RequestFormat = WebMessageFormat.Xml, ResponseFormat = WebMessageFormat.Xml, UriTemplate = "/AddTagtoGroup{group}{tag}")] void AddTagtoGroup(string group, string tag);

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  • User Defined Conversions in C++

    - by wash
    Recently, I was browsing through my copy of the C++ Pocket Reference from O'Reilly Media, and I was surprised when I came across a brief section and example regarding user-defined conversion for user-defined types: #include <iostream> class account { private: double balance; public: account (double b) { balance = b; } operator double (void) { return balance; } }; int main (void) { account acc(100.0); double balance = acc; std::cout << balance << std::endl; return 0; } I've been programming in C++ for awhile, and this is the first time I've ever seen this sort of operator overloading. The book's description of this subject is somewhat brief, leaving me with a few unanswered questions about this feature: Is this a particularly obscure feature? As I said, I've been programming in C++ for awhile and this is the first time I've ever come across this. I haven't had much luck finding more in-depth material regarding this. Is this relatively portable? (I'm compiling on GCC 4.1) Can user-defined conversions to user defined types be done? e.g. operator std::string () { /* code */ }

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  • Port scanning using threadpool

    - by thenry
    I am trying to run a small app that scans ports and checks to see if they are open using and practicing with threadpools. The console window will ask a number and scans ports from 1 to X and will display each port whether they are open or closed. My problem is that as it goes through each port, it sometimes stops prematurely. It doesn't stop at just one number either, its pretty random. For example it I specify 200. The console will scroll through each port then stops at 110. Next time I run it, it stops at 80. Code Left out some of the things, assume all variables are declared where they should. First part is in Main. static void Main(string[] args) { string portNum; int convertedNum; Console.WriteLine("Scanning ports 1-X"); portNum = Console.ReadLine(); convertedNum = Convert.ToInt32(portNum); try { for (int i = 1; i <= convertedNum; i++) { ThreadPool.QueueUserWorkItem(scanPort, i); Thread.Sleep(100); } } catch (Exception e) { Console.WriteLine("exception " + e); } } static void scanPort(object o) { TcpClient scanner = new TcpClient(); try { scanner.Connect("127.0.0.1",(int)o); Console.WriteLine("Port {0} open", o); } catch { Console.WriteLine("Port {0} closed",o); } } }

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  • Compile time error: cannot convert from specific type to a generic type

    - by Water Cooler v2
    I get a compile time error with the following relevant code snippet at the line that calls NotifyObservers in the if construct. public class ExternalSystem<TEmployee, TEventArgs> : ISubject<TEventArgs> where TEmployee : Employee where TEventArgs : EmployeeEventArgs { protected List<IObserver<TEventArgs>> _observers = null; protected List<TEmployee> _employees = null; public virtual void AddNewEmployee(TEmployee employee) { if (_employees.Contains(employee) == false) { _employees.Add(employee); string message = FormatMessage("New {0} hired.", employee); if (employee is Executive) NotifyObservers(new ExecutiveEventArgs { e = employee, msg = message }); else if (employee is BuildingSecurity) NotifyObservers(new BuildingSecurityEventArgs { e = employee, msg = message }); } } public void NotifyObservers(TEventArgs args) { foreach (IObserver<TEventArgs> observer in _observers) observer.EmployeeEventHandler(this, args); } } The error I receive is: The best overloaded method match for 'ExternalSystem.NotifyObservers(TEventArgs)' has some invalid arguments. Cannot convert from 'ExecutiveEventArgs' to 'TEventArgs'. I am compiling this in C# 3.0 using Visual Studio 2008 Express Edition.

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  • Will C++0x support __stdcall or extern "C" capture-nothing lambdas?

    - by Daniel Trebbien
    Yesterday I was thinking about whether it would be possible to use the convenience of C++0x lambda functions to write callbacks for Windows API functions. For example, what if I wanted to use a lambda as an EnumChildProc with EnumChildWindows? Something like: EnumChildWindows(hTrayWnd, CALLBACK [](HWND hWnd, LPARAM lParam) { // ... return static_cast<BOOL>(TRUE); // continue enumerating }, reinterpret_cast<LPARAM>(&myData)); Another use would be to write extern "C" callbacks for C routines. E.g.: my_class *pRes = static_cast<my_class*>(bsearch(&key, myClassObjectsArr, myClassObjectsArr_size, sizeof(my_class), extern "C" [](const void *pV1, const void *pV2) { const my_class& o1 = *static_cast<const my_class*>(pV1); const my_class& o2 = *static_cast<const my_class*>(pV2); int res; // ... return res; })); Is this possible? I can understand that lambdas that capture variables will never be compatible with C, but it at least seems possible to me that capture-nothing lambdas can be compatible.

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  • dynamic inheritance without touching classes

    - by Jasper
    I feel like the answer to this question is really simple, but I really am having trouble finding it. So here goes: Suppose you have the following classes: class Base; class Child : public Base; class Displayer { public: Displayer(Base* element); Displayer(Child* element); } Additionally, I have a Base* object which might point to either an instance of the class Base or an instance of the class Child. Now I want to create a Displayer based on the element pointed to by object, however, I want to pick the right version of the constructor. As I currently have it, this would accomplish just that (I am being a bit fuzzy with my C++ here, but I think this the clearest way) object->createDisplayer(); virtual void Base::createDisplayer() { new Displayer(this); } virtual void Child::createDisplayer() { new Displayer(this); } This works, however, there is a problem with this: Base and Child are part of the application system, while Displayer is part of the GUI system. I want to build the GUI system independently of the Application system, so that it is easy to replace the GUI. This means that Base and Child should not know about Displayer. However, I do not know how I can achieve this without letting the Application classes know about the GUI. Am I missing something very obvious or am I trying something that is not possible?

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  • How to cancel a deeply nested process

    - by Mystere Man
    I have a class that is a "manager" sort of class. One of it's functions is to signal that the long running process of the class should shut down. It does this by setting a boolean called "IsStopping" in class. public class Foo { bool isStoping void DoWork() { while (!isStopping) { // do work... } } } Now, DoWork() was a gigantic function, and I decided to refactor it out and as part of the process broke some of it into other classes. The problem is, Some of these classes also have long running functions that need to check if isStopping is true. public class Foo { bool isStoping void DoWork() { while (!isStopping) { MoreWork mw = new MoreWork() mw.DoMoreWork() // possibly long running // do work... } } } What are my options here? I have considered passing isStopping by reference, which I don't really like because it requires there to be an outside object. I would prefer to make the additional classes as stand alone and dependancy free as possible. I have also considered making isStopping a property, and then then having it call an event that the inner classes could be subscribed to, but this seems overly complex. Another option was to create a "Process Cancelation Token" class, similar to what .net 4 Tasks use, then that token be passed to those classes. How have you handled this situation? EDIT: Also consider that MoreWork might have a EvenMoreWork object that it instantiates and calls a potentially long running method on... and so on. I guess what i'm looking for is a way to be able to signal an arbitrary number of objects down a call tree to tell them to stop what they're doing and clean up and return.

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