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  • Do I really have to call Focus in OnMouseDown of my custom Control?

    - by Thomas
    I'm implementing a custom control that inherits from Control. I want it to be focusable (it's a kind of list box). In the constructor, I do SetStyle(ControlStyles.Selectable, true); I can now use Tab to navigate to the control. However, when the control receives a mouse click, it does not automatically claim focus. I can work around this, of course: protected override void OnMouseDown(MouseEventArgs e) { Focus(); base.OnMouseDown(e); } But this feels like a kludge that should not be necessary. Is this really the way to go? Or is there some way to tell Control to claim focus automatically when it receives a mouse click?

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  • Copy method optimization in compilers

    - by Dženan
    Hi All! I have the following code: void Stack::operator =(Stack &rhs) { //do the actual copying } Stack::Stack(Stack &rhs) //copy-constructor { top=NULL; //initialize this as an empty stack (which it is) *this=rhs; //invoke assignment operator } Stack& Stack::CopyStack() { return *this; //this statement will invoke copy contructor } It is being used like this: unsigned Stack::count() { unsigned c=0; Stack copy=CopyStack(); while (!copy.empty()) { copy.pop(); c++; } return c; } Removing reference symbol from declaration of CopyStack (returning a copy instead of reference) makes no difference in visual studio 2008 (with respect to number of times copying is invoked). I guess it gets optimized away - normally it should first make a copy for the return value, then call assignment operator once more to assign it to variable sc. What is your experience with this sort of optimization in different compilers? Regards, Dženan

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  • Allowing Xform controls for optional XML elements

    - by Cam
    Hi, In designing an XForm interface to an XML database (using eXist and XSLTForms), I'd like to include an input control for an optional element. The XML data records already exist and while some contain the optional element, others don't. To update a record, I'm using the existing XML record as the model instance. The problem is that the form control is not displayed when the optional element is not present, which is logical, but presents a problem when a user wants to add data to the optional element. To be more explicit, here's an example data record, data.xml: <a> <b>content</b> </a> with RNC schema: start = element a { element b { text }, element notes { text }? } XForms model: <xf:model> <xf:instance xmlns="" src="data.xml"/> <xf:submission id="save" method="post" action="update.xq" /> </xf:model> And control: <xf:input ref="/a/notes"> <xf:label>Notes (optional): </xf:label> </xf:input> The problem is that the 'Notes' input control is simply not displayed. An obvious solution is to add a trigger button to allow the user to insert the element if needed, but it is preferable to just have the input control appear, and be empty. My question is: is there some subtle combination of lesser-know attributes/binds/multiple instances/xpath expressions that will cause the control to always be displayed? Thanks

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  • C++/Qt - Memory allocation question

    - by HardCoder1986
    Hello! I recently started investigating Qt for myself and have the following question: Suppose I have some QTreeWidget* widget. At some moment I want to add some items to it and this is done via the following call: QList<QTreeWidgetItem*> items; // Prepare the items QTreeWidgetItem* item1 = new QTreeWidgetItem(...); QTreeWidgetItem* item2 = new QTreeWidgetItem(...); items.append(item1); items.append(item2); widget->addTopLevelItems(items); So far it looks ok, but I don't actually understand who should control the objects' lifetime. I should explain this with an example: Let's say, another function calls widget->clear();. I don't know what happens beneath this call but I do think that memory allocated for item1 and item2 doesn't get disposed here, because their ownage wasn't actually transfered. And, bang, we have a memory leak. The question is the following - does Qt have something to offer for this kind of situation? I could use boost::shared_ptr or any other smart pointer and write something like shared_ptr<QTreeWidgetItem> ptr(new QTreeWidgetItem(...)); items.append(ptr.get()); but I don't know if the Qt itself would try to make explicit delete calls on my pointers (which would be disastrous since I state them as shared_ptr-managed). How would you solve this problem? Maybe everything is evident and I miss something really simple?

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  • Dealloc'd Predicate crashing iPhone App!

    - by DVG
    To preface, this is a follow up to an inquiry made a few days ago: http://stackoverflow.com/questions/2981803/iphone-app-crashes-when-merging-managed-object-contexts Short Version: EXC_BAD_ACCESS is crashing my app, and zombie-mode revealed the culprit to be my predicate embedded within the fetch request embedded in my Fetched Results Controller. How does an object within an object get released without an explicit command to do so? Long Version: Application Structure Platforms View Controller - Games View Controller (Predicated upon platform selection) - Add Game View Controller When a row gets clicked on the Platforms view, it sets an instance variable in Games View for that platform, then the Games Fetched Results Controller builds a fetch request in the normal way: - (NSFetchedResultsController *)fetchedResultsController{ if (fetchedResultsController != nil) { return fetchedResultsController; } //build the fetch request for Games NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Game" inManagedObjectContext:context]; [request setEntity:entity]; //predicate NSPredicate *predicate = [NSPredicate predicateWithFormat:@"platform == %@", selectedPlatform]; [request setPredicate:predicate]; //sort based on name NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; //fetch and build fetched results controller NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:context sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; [sortDescriptor release]; [sortDescriptors release]; [predicate release]; [request release]; [aFetchedResultsController release]; return fetchedResultsController; } At the end of this method, the fetchedResultsController's _fetch_request - _predicate member is set to an NSComparisonPredicate object. All is well in the world. By the time - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section gets called, the _predicate is now a Zombie, which will eventually crash the application when the table attempts to update itself. I'm more or less flummoxed. I'm not releasing the fetched results controller or any of it's parts, and the only part getting dealloc'd is the predicate. Any ideas?

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  • contain new elements of an "instance" in javascript

    - by iamnotmad
    Hi, so I know there are tons of ways to simulate inheritance and other OO features. I have chosen one to use for my project and am wondering if I can create an instance and add stuff to it and keep it contained (within braces). Consider the following: function BaseClass(){ <this.stuff here> } function SubClass(){ this.superClass = BaseClass(); this.superClass(); <this.other stuff here> } myObj = new SubClass(); so myObj is an instance of SubClass. I can add things to myObj like: myObj.blah = "funtimes"; What I would like is to be able to add stuff to the "instance" and keep it organized in braces much like the constructor. psuedo code like: myObj = new SubClass() { var blah = "funtimes" <more instance specific stuff here> } Is something like this possible? Thanks!

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  • C++ creating generic template function specialisations

    - by Fire Lancer
    I know how to specialise a template function, however what I want to do here is specialise a function for all types which have a given method, eg: template<typename T> void foo(){...} template<typename T, if_exists(T::bar)>void foo(){...}//always use this one if the method T::bar exists T::bar in my classes is static and has different return types. I tried doing this by having an empty base class ("class HasBar{};") for my classes to derive from and using boost::enable_if with boost::is_base_of on my "specialised" version. However the problem then is that for classes that do have bar, the compiler cant resolve which one to use :(. template<typename T> typename boost::enable_if<boost::is_base_of(HasBar, T>, void>::type f() {...} I know that I could use boost::disable_if on the "normal" version, however I do not control the normal version (its provided by a third party library and its expected for specialisations to be made, I just don't really want to make explicit specialisations for my 20 or so classes), nor do I have that much control over the code using these functions, just the classes implementing T::bar and the function that uses it. Is there some way to tell the compiler to "always use this version if possible no matter what" without altering the other versions?

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  • Syncing JS+PHP time

    - by meder
    Since the Date constructor is based on your PC's timezone and server-side is obviously dependent on the server's time settings... What procedures can I do to ensure that the timestamps I generate are consistent on both ends? I have a jQuery datepicker setup and I do a lot of work, I also have my own datepicker that's generated from server-side code which looks up db availability for bookings. I'm saving arrival/departure times on the server-side and the days are off by one because the JS is local timezone ( mine is Eastern ) . Is my only option doing something like making the JS call PHP to grab a timestamp?

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  • are Hierarchical SIngletons in Java possible?

    - by Zach H
    I've been toying with an interesting idea (No idea if I'll include it in any code, but it's fun to think about) Let's say we have a program that requires a large number of classes, all of a certain subclass. And those classes all need to be singletons. Now, we could write the singleton pattern for each of those classes, but it seems wasteful to write the same code over and over, and we already have a common base class. It would be really nice to create a getSingleton method of A that when called from a subclass, returns a singleton of the B class (cast to class A for simplicity) class A{ public A getSingleton(){ //Wizardry } } class B extends A{ } A blargh = B.getSingleton() A gish = B.getSingleton() if(A == B) System.out.println("It works!") It seems to me that the way to do this would be to recognize and call B's default constructor (assuming we don't need to pass anything in.) I know a little of the black magic of reflection in Java, but i'm not sure if this can be done. Anyone interested in puzzling over this?

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  • [Qt] How to make another window pop up that extends QWidget as opposed to QDialog?

    - by Graphics Noob
    So far I've only had my main window pop up other windows that were QDialogs and I'm not getting it to work with a QWidget. The other window I want to display was designed with the Form Editor, then wrapped in a class called ResultViewer which extends QWidget (as opposed to QDialog). What I want is to have the ResultViewer show its ui in a seperate window. Now when I try to display it the ResultViewer ui just pops up in the main window on top of the mainwindow ui. The code I'm using to display it is this (in my mainwindow.cpp file) ResultViewer * rv = new ResultView(this); rv->show(); The constructor for the ResultViewer looks like this ResultViewer::ResultViewer(QWidget * parent) : QWidget(parent), ui(new Ui::ResultViewer) { ui->setupUi(this); } I've looked through the QWidget documentation a bit but the only thing I can find that may be related is the QWidget::window() function, but the explanation isn't very clear, it just gives an example of changing the title of a window.

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  • Circle class in java

    - by user292395
    I need to get the Java code for the below problem asap. Create a class Circle that will allow us to define a circle with a specific radius. Your class should include the following methods: A constructor that can create a circle with a specified radius. A method setRadius that sets a specific value as a new radius for an existing circle. A method getRadius that returns the radius of an existing circle. A method toString that returns a String with all the information about an existing circle. A method computeArea that computes the area of a circle A method computePerimeter that computes the perimeter of a circle.

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  • MVC Pages that require the user to be logged in

    - by keithjgrant
    I'm working on a little MVC framework and I'm wondering what the "best way" is to structure things so secure pages/controllers always ensure the user is logged in (and thus automatically redirects to a login page--or elsewhere--if not). Obviously, there are a lot of ways to do it, but I'm wondering what solution(s) are the most common or are considered the best practice. Some ideas I had: Explicitly call user->isLoggedIn() at the beginning of your controller action method? (Seems far too easy to forget and leave an important page unsecure on accident) Make your controller extend a secureController that always checks for login in the constructor? Do this check in the model when secure information is requested? (Seems like redundant calls would be made) Something else entirely? Note: I'm working in PHP, though the question is not language-dependent.

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  • Real-world examples of populating a GWT CellTable using a clean MVP pattern?

    - by piehole
    We are using the GWT-Presenter framework and attempting to use CellTable to put together an updateable grid. It seems as though several of the GWT constructs for CellTable don't lend themselves to easily breaking up the logic into clean view and presenter code. Examples: 1) Within the View's constructor, the CellTable is defined and each column is created by anonymous inner classes that extend the Column class to provide the onValue() method. 2) The FieldUpdater interface must be implemented to provide logic to execute when a user alters data in a cell. This seems like it would best fit in the Presenter's onBind() method, but FieldUpdaters often need access to the Cell or Column which belong in the view. CellTable does not have accessor methods to get hold of the Columns or Cells, so it seems the only way for the Presenter to get them is for me to create a multitude of member variables on the View and accessors on my Display interface. Can anyone provide good examples for dealing with CellTable in GWT-Presenter or a comparable MVP

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  • Communication between Multiple Threads in a WPF Application

    - by Robert
    I'm creating a WPF application that uses a custom object to populate all the controls. The constructor of that object is initiated by an EventHandler that waits for an API. The problem I'm having is when I try to access any information from that object using a button for example, it returns an error saying "The calling thread cannot access this object because a different thread owns it". I'm assuming this is because the EventHandler creates a new thread which doesn't allow the Main Thread to have access to it. Any ideas on how to get around this? I'm basically having the error "The calling thread cannot access this object because a different thread owns it" when trying to get or set a CollectionViewSource.

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  • can't create partial objects with accepts_nested_attributes_for

    - by Isaac Cambron
    I'm trying to build a form that allows users to update some records. They can't update every field, though, so I'm going to do some explicit processing (in the controller for now) to update the model vis-a-vis the form. Here's how I'm trying to do it: Family model: class Family < ActiveRecord::Base has_many :people, dependent: :destroy accepts_nested_attributes_for :people, allow_destroy: true, reject_if: ->(p){p[:name].blank?} end In the controller def check edited_family = Family.new(params[:family]) #compare to the one we have in the db #update each person as needed/allowed #save it end Form: = form_for current_family, url: check_rsvp_path, method: :post do |f| = f.fields_for :people do |person_fields| - if person_fields.object.user_editable = person_fields.text_field :name, class: "person-label" - else %p.person-label= person_fields.object.name The problem is, I guess, that Family.new(params[:family]) tries to pull the people out of the database, and I get this: ActiveRecord::RecordNotFound in RsvpsController#check Couldn't find Person with ID=7 for Family with ID= That's, I guess, because I'm not adding a field for family id to the nested form, which I suppose I could do, but I don't actually need it to load anything from the database for this anyway, so I'd rather not. I could also hack around this by just digging through the params hash myself for the data I need, but that doesn't feel a slick. It seems nicest to just create an object out of the params hash and then work with it. Is there a better way? How can I just create the nested object?

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  • Java - Confused by the one class per file rule

    - by Mark
    The one class per file rule in Java has me a bit confused. I writing an Android app and trying to implement the accepted answer to this question: Common class for AsyncTask in Android? which calls for an interface definition which class A implements and class B accepts as an argument to its constructor. So I need an A.java and a B.java, but where does the interface go? Does it need a separate java file itself? Do I have to define it inside both A and B? If not how to import it? Also I will have about 10 different AsyncTask classes, but I don't want to bother creating a new file for each one. What would you recommend? Is there a way to put all 10 classes in one file? Or should I create a big if/then block inside the class and pass an argument telling it which of the 10 different tasks I want it to do?

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  • Change a registry value in vb.net

    - by mhofer
    Hello, I have searched a lot to find a solution for my problem, but I can't find any specific solution. I need to change a value which is stored under HKEY_LOCAL_MACHINE\SOFTWARE\APP_NAME. It is not possible to use .NET's registry functions, since they have drastic restrictions. The following snippet should solve my problem: Dim regKey As RegistryKey Dim ver As Decimal regKey = My.Computer.Registry.LocalMachine.OpenSubKey("HKEY_LOCAL_MACHINE\SOFTWARE\APP_NAME", True) regKey.SetValue("IP", "192.168.10.15:18500") regKey.Close() Unfortunately, I get a NullReferenceExeption when I try to set the value. What should I do? I have imported Microsoft.Win32 and RegistryKey doesn't accept any constructor... cheers mike

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  • copy rows with special condition

    - by pooria_googooli
    I have a table with a lot of columns. For example I have a table with these columns : ID,Fname,Lname,Tel,Mob,Email,Job,Code,Company,...... ID column is auto number column. I want to copy all rows in this table to this table and change the company column value to 12 in this copied row. I don't want to write name all of the columns because I have a lot of table with a lot of columns. I tried this code but I had this error : declare @c int; declare @i int; select * into CmDet from CmDet; select @C= count(id) from CmDet; while @i < @C begin UPDATE CmDet SET company =12 WHERE company=11 set @i += 1 end error : Msg 2714, Level 16, State 6, Line 3 There is already an object named 'CmDet' in the database. I changed the code to this declare @c int declare @i int insert into CmDet select * from CmDet; select @C= count(id) from CmDet; while @i < @C begin UPDATE CmDet SET company =12 WHERE company=11 set @i += 1 end and I had this error : Msg 8101, Level 16, State 1, Line 3 An explicit value for the identity column in table 'CmDet' can only be specified when a column list is used and IDENTITY_INSERT is ON. What should I do ?

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  • C++: use array of strings wrapped in namespace?

    - by John D.
    I got the following code, wishing to wrap a group of strings nicely in a namespace: namespace msgs { const int arr_sz = 3; const char *msg[arr_sz] = {"blank", "blank", "blank" }; msg[0] = "Welcome, lets start by getting a little info from you!\n"; msg[1] = "Alright, bla bla bla.."; msg[2] = "etc."; } The code inside works nicely inside a function, but I don't know how to return an array from it. The namespace idea LOOKS fine, but it returns on the last three lines: error: expected constructor, destructor, or type conversion before ‘=’ token Why can't I define the array inside a namespace, do I need to do something first? It's nice because I can call it like printf(msgs::msg[1]) etc. I want to do this I just can't wrap my head around what's wrong :(

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  • Not getting image in h:graphicImage in JSF

    - by Nitesh Panchal
    Hello, I have this very strange error with h:graphicImage This code works fine :- <h:graphicImage value="/Common/Images/#{item.templatePicName}"/> And this one doesn't :- <h:graphicImage alt="${app:getCommonImagePath(item.templatePicName)}" value="${app:getCommonImagePath(item.templatePicName)}" /> It only shows alt value /Common/Images/Sunset.jpg which is perfectly fine and works in 1st case. Then why doesn't it work in 2nd case? There are no problems with my images. They are present in right directory. here getCommonImagePath is my custom EL function, whose definition is : package Common; public final class AppDeployment { private AppDeployment(){ //hide constructor } private static String commonImageFolderPath = "/Common/Images/"; public static String getCommonImagePath(String picName){ return commonImageFolderPath + picName; } }

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  • Java - Does null variable require space in memory

    - by Yatendra Goel
    class CheckStore { private String displayText; private boolean state; private String meaningfulText; private URL url; public CheckStore(String text, boolean state) { this.displayText = text; this.state = state; } : : } As I am initializing only two variables (displayText and state) in the constructor, Will the rest two variables (meaningfulText and url which will have the value null) will require space in memory to store null value. Q1. I think they will require space. If they will, then how much memory does a null value takes in the memory (like int takes 4 bytes). Q2. How much space a string takes in memory. I guess it will depend on the length of the string. So how much space a string takes of how much length?

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  • OBject access from different functions in VC++

    - by sijith
    Hi, I have 3 function in my class B. These three function have to access member function of other class A. I did this by creating object of class A in class B constructor and tried to access that object in functions of class B. But its showing error. How can i assess the same object in these three functions. Where i have to create object of class A B::B() { A a; } B:: function() { a.fun(); //fun belongs to class A } B:: function1() { a.fun1(); //fun1 belongs to class A } I am getting error, How can i implement the same where i can access object a in both function.

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  • Qt "no matching function for call"

    - by Blin
    I have no matching function for call to 'saveLine::saveLine()' error when compiling my application. The construcor is never actually called. saveLine class definition: class saveLine { public: saveLine(QWidget *parent); private: QPushButton *selectButton, *acceptButton; QLabel *filePath; QLineEdit *allias; }; saveLine is used in another class which is defined as follows: class MWindow : public QWidget { Q_OBJECT public: MWindow(QWidget *parent=0); private: saveLine line1; }; error points to MWindow constructor implementation MWindow::MWindow(QWidget *parent):QWidget(parent) { this->setWindowTitle("Launcher"); this->resize(600,600); } What should i do? I intend to use saveLine class in a vector, to create lines at runtime.

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  • How to order my objects in a C++ class correctly

    - by Julen
    Hello, I have been coding regurlarly in C++ in the past months. I am getting used to it step by step... but there are things that confuse me about formatting. I know there is a lot of legacy from C that I supousee mixes with C++. This time I have doubts about how to order properly my members and functions within in a class. Also considering their access modifiers. How is the convention in this? Until know I am doing everything "public" and writing first constructor of class, then destructor, next members and finally functions. It this correct? What happens when introducing "private" and "protected" access modifiers or "virtual" functions? From the documents I have look in the Internet there is different ways of doing things. But my questions aims to get the knowledge from a community that develops in C++ that I want to blend into. ;-) Thanks a lot!!!

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  • How do I obtain an HtmlHelper<TModel> instance for a model in ASP.NET MVC?

    - by DanM
    Let's say I have an Index view. The model I pass in is actually a collection of models, so the Html property is of type HtmlHelper<List<MyModel>>. If I want to call extension methods (e.g., Display() or DisplayFor() on the individual items in the list, however, I think I need to obtain an HtmlHelper<MyModel>. But how? I tried using the HtmlHelper<TModel> constructor, which looks like this: HtmlHelper<TModel>(ViewContext, IViewDataContainer) But I'm not having any luck with that. I don't know how to obtain the IViewDataContainer for the item, and the documentation on these things is very sparse. A lot of magic apparently happens when I do... return View(List<MyModel>); ...in my controller. How do I recreate that magic on individual items in a list/collection?

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