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• WPF UserControl event called only once?

  - by 742

  Hi Everyone, I need to bind two-way a property of a user control to a property of a containing user control. I also need to set a default value to the property from code in the child (cannot be done easily from XAML tags). If I call my code from the child constructor, the value is set in the parent but the change callback routine is not triggered (my understanding is that the parent doesn't yet exist at the time the child is created). My current workaround is to catch the Loaded event of the child and to call the code from the handler. Howver as Loaded is called more than once, I need to set a flag to set the property only the first time. I don't like this way, but I don't know if there is a single shot event that could be used, or if this can be done otherwise. Any feedback based on your experience?

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• How to default-initialize local variables of built-in types in C++?

  - by sharptooth

  How do I default-initialize a local variable of primitive type in C++? For example if a have a typedef: typedef unsigned char boolean;//that's Microsoft RPC runtime typedef I'd like to change the following line: boolean variable = 0; //initialize to some value to ensure reproduceable behavior retrieveValue( &variable ); // do actual job into something that would automagically default-initialize the variable - I don't need to assign a specific value to it, but instead I only need it to be intialized to the same value each time the program runs - the same stuff as with a constructor initializer list where I can have: struct Struct { int Value; Struct() : Value() {} }; and the Struct::Value will be default-initialized to the same value every time an instance is cinstructed, but I never write the actual value in the code. How can I get the same behavior for local variables?

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• Google App Engine datastore-primary key

  - by megala

  Hi, I've created a table in the Google App Engine Datastore. It contains the following FIELDS(GROUPNAME,GROUPID,GROUPDESC). How do I set GROUPID as the primary key? My code is as follows: @Entity @Table(name="group" , schema="PUBLIC") public class Creategroup { @Basic private String groupname; @Basic private String groupid; @Basic private String groupdesc; public void setGroupname(String groupname) { this.groupname = groupname; } public String getGroupname() { return groupname; } public void setGroupid(String groupid) { this.groupid = groupid; } public String getGroupid() { return groupid; } public void setGroupdesc(String groupdesc) { this.groupdesc = groupdesc; } public String getGroupdesc() { return groupdesc; } public Creategroup(String groupname, String groupid, String groupdesc ) { // TODO Auto-generated constructor stub this.groupname = groupname; this.groupid = groupid; this.groupdesc = groupdesc; } }

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• Avoid Flickering in Windows Forms?

  - by user1733909

  Double buffering not working with combo-box. is there any another methods to avoid flickering in windows forms? i have one windows form with number of panels in it. I'm showing only one panel at a time based on my menu selection. i have one icon panel,one header panel and the combo box. based on the selected item of that combo-box the gridview1 and 2 are filling. when I'm rapidly selecting the combo-box item using my keyboard down arrow the icon panel and the header panel are always repainting. i need to keep that both without any change. this two panels producing some flashing effect(ie,they are blinking or flashing) while I'm changing the combo box selected index. is there any way to avoid this flashing.? i tried double-buffered enabled in form constructor and form load event. Please Help..............

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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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• How to make TObjectDictionary.Values accessible as property?

  - by Holgerwa

  I have an object like this: TMyObj = class private FObjList: TObjectDictionary <integer, TMyObject>; public constructor Create; destructor Destroy; // How to access Values correctly? Something similar to this not working code property Values: TValueCollection read FObjList.Values write FObjList.Values; end; var MyObj: TMyObj; To access the values of FObjList, I'd like to write: for tmpObject in MyObj.Values do ... How do I need to declare the property "Values" so that MyObj.Values behaves exactly as if I would access MyObj.FObjList.Values?

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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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• 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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• Cant append "used" DOMObject in IE

  - by Kein

  I have some objects, that keep created DOMObjects, like here: function category(){ var domBlock; this.block = function(){ if (!domBlock){ // Here dom-object constructor $('<div></div>'); etc } return domBlock; // jquery object, // but i test and native document.createElement } } Then i clear category's area, and append old and new received(with Ajax) objects: area.html(''); for(id in category_list){ area.append( category_list[id].block() ); } where category_list is list that contain category objects. Area is jQuery object. In other browsers (except IE) i get area with all needed categories, but in IE i get only new received categories(that just create DomObject), other old objects that keeped old DomObject not show. I know it possible make with innerHTML, but i wont keep DomObject, not text. Because DomObject keep many events. And it very hard for browser attach events for each DomObject after refresh area.

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• Does C++ require a destructor call for each placement new?

  - by Josh Haberman

  I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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• How does one refer to the game1 class's variables in XNA

  - by user1149068

  I try to refer to an array in the Game1 class by creating an object of the Game1 class with its definition Game1 gameObject; , its declaration gameObject = new Game1(); in the constructor, and its usage gameObject.tileArray[xInt, yInt].treed = true;. The game1 class itself remains unchanged in its class code other than some methods and variables. When I try to use this code in the TreeRegion class it gives me "Object reference not set to an instance of an object," leading me to believe that the game1 class is null somehow. How might one change the class or object in order to refer to game1's variables? Mind you I am self-taught and still rather new to C#. The class that refers to game1: http://pastebin.com/0chEcKfq Game1 itself http://pastebin.com/zLDVzCca

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• XPathDocument behavior with DOCTYPE declaration

  - by gliderkite

  I use XPathDocument to parse an XML file, but if there's a doctype declaration, when I initializes a new instance of the XPathDocument class passing the path of the file, that contains the XML data, to its constructor, my application tries to connect to internet (probably to verify the correctness of the XML data) and remains blocked for a long period of time. This does not occur if I delete the doctype declaration from the XML file. XmlDocument.Load method has the same behavior. How can I fix this problem? Thanks.

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• Why would a 'public event EventHandler cccc' be null?

  - by Matt

  Why would a 'public event EventHandler cccc' be null? I have a class that's public class Builder { public event EventHandler StartedWorking; public Builder() { // Constructor does some stuff } public void Start() { StartedWorking(this, eventargobject); //StartedWorking is null -- } } This seems straightforward and something I do all the time? Am I missing something obvious or is there something that could cause this? EDIT: Does this mean that if I fire an event that is not subscribed to in a client class I have to check that it is not null? EDIT-2: I guess I'd never had events that were never not subscribed to and hence never ran into this -- You learn something new every day Sorry about the seemingly stupid question....

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• what is serialization and how it works

  - by Rozer

  I know the serialization process but have't implemented it. In my application i have seen there are various classes that has been implemented serilizable interface. consider following class public class DBAccessRequest implements Serializable { private ActiveRequest request = null; private Connection connection = null; private static Log log = LogFactory.getLog(DBAccessRequest.class); public DBAccessRequest(ActiveRequest request,Connection connection) { this.request = request; this.connection = connection; } /** * @return Returns the DB Connection object. */ public Connection getConnection() { return connection; } /** * @return Returns the active request object for the db connection. */ public ActiveRequest getRequest() { return request; } } just setting request and connection in constructor and having getter setter for them. so what is the use of serilizable implementation over here...

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• How to use SQLiteOpenHelper without or less restrictive use of Context?

  - by Pentium10

  If you extend SQLiteOpenHelper, for the Constructor you have to use a Context. I am wondering if there is a way to leave this out, and be able to work with database tables without a Context. Or at least be least restrictive, I mean a way of project/class structure that will make history the several context passings I have to do now. As it is my application has several level of classes, chained in each other, and there are a few that connects to the database, but have no whatsoever influence on the interface, so they don't actually need the Context. Are you creating your classes in the way that you pass each time a Context to them? If not, how you do, how you reuse a Context in a short class?

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• passing parameters to a thread

  - by assassin

  I want to pass a function that takes a parameter to the ThreadStart Constructor in C#. But, it seems that this is not possible, as I get a syntax error it I try to do something like this Thread t1 = new Thread(new Thread Start(func1(obj1)); where obj1 is an object of type List<string> (say). If I want a thread to execute this function that takes in an object as a parameter, and I plan to create 2 such threads simultaneously with different parameter values what is the best method to achieve this?

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• Using pipes inside a class in C++

  - by Paul

  I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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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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• 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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• Confusion using MYSQLI

  - by user1020069

  I just started using mysqli API for PHP. Apparently, every time an object of the class MYSQLI is instantiated, it can setup a connection to the database as it connects to the server unlike mysql_connect, which connects to the server first and then you are required to specify the database to query. Now this is a good problem if the db exists, in my case, the db does not exist on the first ever connection to the server/execution of the problem, hence I must connect without specifying the database, which is fine, since the msyqli constructor does not make this database mandatory. My challenge is essentially, how do I check if the database exists before attempting the first connection. The only way to really do this would be to establish a conection to the server and then use the result of the following query to gauge if the database exists: SELECT COUNT(*) AS `exists` FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMATA.SCHEMA_NAME="dbname" ; If this returns true, then the database exists, but now the challenge is how do I get the mysqli object to query this database rather than having to prefix the name of the database in the query. Thanks much

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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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• [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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• 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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• Explicitly persist states in Workflow 4.0 rather than everything.

  - by jlafay

  I have ran into an issue with my SQL instance store attached to a WorkflowApplication that is running. When I exit my application I'm calling an Unload() on the WF app to persist it. I didn't think about it during design time, but it does makes sense, it's persisting an arg that was passed in to the WorkflowApplication constructor when instanced. When the application runs, everything in the workflow works as expected. When I call Unload() I get an unhandled exception that states that the arg is not serializable and needs [DataContractAttribute]. What's passed into the workflow is my applications custom logger object that I wrote so that the WF can log to disk in a uniform way that I prefer. How do I prevent the workflow app from persisting this one argument and persist everything else? I'm sure something can be done with extensions but I'm having a hard time finding info on them or finding persistence examples for my scenario.

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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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