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• Send keystrokes to TextBox

  - by tanascius

  I have a derived TextBox where I intercept the userinput to manipulate it. However I have to preserve the original typed input. So my idea was to hold an inner TextBox within my derived class and send the user's input to that TextBox before manipulating it. The reason for this approach is that I do not want to take care of all this special actions like: typing something, ctrl+a, [del], type something else, [backspace] and so on ... However I do not know how to send a single keystroke (keycode, ascii, char) to a TextBox. Maybe you have another idea without an inner TextBox at all? Thank you!

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• Sandcastle not adding param documentation

  - by rockinthesixstring

  My method looks as follows ''' <summary> ''' Adds the activity. ''' </summary> ''' <param name="userid">An that is derived from the <see cref="Domain.User.ID" /></param> ''' <param name="activity">The activity integer that is to be derived from the <see cref="ActivityLogService.LogType" />.</param> ''' <param name="ip">An IP V4 IP Address.</param>integer ''' <remarks></remarks> Public Sub AddActivity(ByVal userid As Integer, ByVal activity As Integer, ByVal ip As String) Implements IActivityLogService.AddActivity Dim _activity As ActivityLog = New ActivityLog _activity.Activity = activity _activity.UserID = userid _activity.UserIP = ip.IPAddressToNumber _activity.ActivityDate = DateTime.UtcNow ActivityLogRepository.AddActivity(_activity) End Sub But when I run Sandcastle, my documentation ends up looking like this userid Type: System..::..Int32 [Missing documentation for "M:myapp.Core.Domain.ActivityLogService.AddActivity(System.Int32,System.Int32,System.String)"] activity Type: System..::..Int32 [Missing documentation for "M:myapp.Core.Domain.ActivityLogService.AddActivity(System.Int32,System.Int32,System.String)"] ip Type: System..::..String [Missing documentation for "M:myapp.Core.Domain.ActivityLogService.AddActivity(System.Int32,System.Int32,System.String)"] What am I doing wrong?

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• C++ Virtual Constructor, without clone()

  - by Julien L.

  I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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• Problem deriving a user control from an abstract base class in website project

  - by Sprintstar

  In a Visual Studio website, I have created a user control. This control is derived from a class (in App_Code) that is itself derived from System.Web.UI.UserControl. This is an abstract class with an abstract method. I then try to implement that method in the user control, but I get the following errors from Visual Studio: Error 1 'WebUserControl.AbstractMethod()': no suitable method found to override C:\Users\User\Documents\Visual Studio 2010\WebSites\Delme\WebUserControl.ascx.cs 10 28 C:\...\Delme\ Error 2 'WebUserControl' does not implement inherited abstract member 'AbstractBaseClass.AbstractMethod()' c:\Users\User\AppData\Local\Temp\Temporary ASP.NET Files\delme\0eebaa86\f1a48678\App_Web_nrsbzxex.0.cs 14 Error 1 says that my override of the abstract method is invalid, it doesn't recognise the abstract method in the base class. Error 2 says that the partial class automatically built by asp.net doesn't implement the abstract method! Note that this works fine when the code is used in a Web Application project. Why is this happening?

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• Should class IOException in Java have been an unchecked RuntimeException?

  - by Derek Mahar

  Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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• QGraphicsItem doesn't receive mouse hover events

  - by Jen

  I have a class derived from QGraphicsView, which contains QGraphicsItem-derived elements. I want these elements to change color whenever the mouse cursor hovers over them, so I implemented hoverEnterEvent (and hoverLeaveEvent): void MyGraphicsItem::hoverEnterEvent(QGraphicsSceneHoverEvent* event) { update (boundingRect()); } However, this event handler code is never executed. I've explicitly enabled mouse tracking: MyGraphicsView::MyGraphicsView(MainView *parent) : QGraphicsView(parent) { setMouseTracking(true); viewport()->setMouseTracking(true); ... } Still, no luck. What am I doing wrong?

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• Iterator blocks and inheritance.

  - by Dave Van den Eynde

  Given a base class with the following interface: public class Base { public virtual IEnumerable<string> GetListOfStuff() { yield return "First"; yield return "Second"; yield return "Third"; } } I want to make a derived class that overrides the method, and adds its own stuff, like so: public class Derived : Base { public override IEnumerable<string> GetListOfStuff() { foreach (string s in base.GetListOfStuff()) { yield return s; } yield return "Fourth"; yield return "Fifth"; } } However, I'm greeted with a warning that "access to a member through a base keyword from an iterator cannot be verified". What's the accepted solution to this problem then?

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• Database Design Question: GUID + Natural Numbers

  - by Alan

  For a database I'm building, I've decided to use natural numbers as the primary key. I'm aware of the advantages that GUID's allow, but looking at the data, the bulk of row's data were GUID keys. I want to generate XML records from the database data, and one problem with natural numbers is that I don't want to expose my database key's to the outside world, and allow users to guess "keys." I believe GUID's solve this problem. So, I think the solution is to generate a sparse, unique iD derived from the natural ID (hopefully it would be 2-way), or just add an extra column in the database and store a guid (or some other multibyte id) The derived value is nicer because there is no storage penalty, but it would be easier to reverse and guess compared to a GUID. I'm (buy) curious as to what others on SO have done, and what insights they have.

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• C++: Binding to a base class

  - by Helltone

  The following code works, but I'm not sure it is correct/portable. #include <iostream> #include <tr1/functional> class base { public: base(int v) : x(v) {} protected: int x; }; class derived : public base { public: bool test() { return (x == 42); } }; int main(int argc, char* argv[]) { base b(42); if(std::tr1::bind((bool (base::*)()) &derived::test, b)()) { std::cout << "ok\n"; } return 0; }

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• [C++] Multiple inheritance from template class

  - by Tom P.

  Hello, I'm having issues with multiple inheritance from different instantiations of the same template class. Specifically, I'm trying to do this: template <class T> class Base { public: Base() : obj(NULL) { } virtual ~Base() { if( obj != NULL ) delete obj; } template <class T> T* createBase() { obj = new T(); return obj; } protected: T* obj; }; class Something { // ... }; class SomethingElse { // ... }; class Derived : public Base<Something>, public Base<SomethingElse> { }; int main() { Derived* d = new Derived(); Something* smth1 = d->createBase<Something>(); SomethingElse* smth2 = d->createBase<SomethingElse>(); delete d; return 0; } When I try to compile the above code, I get the following errors: 1>[...](41) : error C2440: '=' : cannot convert from 'SomethingElse *' to 'Something *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1> [...](71) : see reference to function template instantiation 'T *Base<Something>::createBase<SomethingElse>(void)' being compiled 1> with 1> [ 1> T=SomethingElse 1> ] 1>[...](43) : error C2440: 'return' : cannot convert from 'Something *' to 'SomethingElse *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast The issue seems to be ambiguity due to member obj being inherited from both Base< Something and Base< SomethingElse , and I can work around it by disambiguating my calls to createBase: Something* smth1 = d->Base<Something>::createBase<Something>(); SomethingElse* smth2 = d->Base<SomethingElse>::createBase<SomethingElse>(); However, this solution is dreadfully impractical, syntactically speaking, and I'd prefer something more elegant. Moreover, I'm puzzled by the first error message. It seems to imply that there is an instantiation createBase< SomethingElse in Base< Something , but how is that even possible? Any information or advice regarding this issue would be much appreciated.

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• Check if a class is subclass of another class in Java

  - by craesh

  Hi! I'm playing around with Java's reflection API and trying to handle some fields. Now I'm stuck with identifying the type of my fields. Strings are easy, just do myField.getType().equals(String.class). The same applies for other non-derived classes. But how do I check derived classes? E.g. LinkedList as subclass of List. I can't find any isSubclassOf(...) or extends(...) method. Do I need to walk through all getSuperClass() and find my supeclass by my own? Thanks! craesh

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• Python: How to run unittest.main() for all source files in a subdirectory?

  - by Pete

  I am developing a Python module with several source files, each with its own test class derived from unittest right in the source. Consider the directory structure: dirFoo\ test.py dirBar\ __init__.py Foo.py Bar.py To test either Foo.py or Bar.py, I would add this at the end of the Foo.py and Bar.py source files: if __name__ == "__main__": unittest.main() And run Python on either source, i.e. $ python Foo.py ........... ---------------------------------------------------------------------- Ran 11 tests in 2.314s OK Ideally, I would have "test.py" automagically search dirBar for any unittest derived classes and make one call to "unittest.main()". What's the best way to do this in practice? I tried using Python to call execfile for every *.py file in dirBar, which runs once for the first .py file found & exits the calling test.py, plus then I have to duplicate my code by adding unittest.main() in every source file--which violates DRY principles.

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• Base form controls not visible in child form

  - by Kildareflare

  Hello I'm using C#.Net and have a base form that is inherited by several forms. Until yesterday, when the child (derived) form was opened in the designer the base forms controls would be displayed and shown as locked. Now, however the form is simply blank. None of the base forms controls are visible in the designer. Everything compiles, builds and runs OK. Has anyone else seen this? I've tried placing a call to the base forms InitializeComponent method in the derived forms OnLoad method but to no avail.

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• std::string vs. char*

  - by Elofin

  does std::string store data differently than a char* on either stack or heap or is it just derived from char* into a class?

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• c++ property class structure

  - by Without me Its just Aweso

  I have a c++ project being developed in QT. The problem I'm running in to is I am wanting to have a single base class that all my property classes inherit from so that I can store them all together. Right now I have: class AbstractProperty { public: AbstractProperty(QString propertyName); virtual QString toString() const = 0; virtual QString getName() = 0; virtual void fromString(QString str) = 0; virtual int toInteger() = 0; virtual bool operator==(const AbstractProperty &rightHand) = 0; virtual bool operator!=(const AbstractProperty &rightHand) = 0; virtual bool operator<(const AbstractProperty &rightHand) = 0; virtual bool operator>(const AbstractProperty &rightHand) = 0; virtual bool operator>=(const AbstractProperty &rightHand) = 0; virtual bool operator<=(const AbstractProperty &rightHand) = 0; protected: QString name; }; then I am implementing classes such as PropertyFloat and PropertyString and providing implementation for the comparator operators based on the assumption that only strings are being compared with strings and so on. However the problem with this is there would be no compiletime error thrown if i did if(propertyfloat a < propertystring b) however my implementation of the operators for each derived class relies on them both being the same derived class. So my problem is I cant figure out how to implement a property structure so that I can have them all inherit from some base type but code like what I have above would throw a compile time error. Any ideas on how this can be done? For those familiar with QT I tried using also a implementation with QVariant however QVariant doesn't have operators < and defined in itself only in some of its derived classes so it didn't work out. What my end goal is, is to be able to generically refer to properties. I have an element class that holds a hashmap of properties with string 'name' as key and the AbstractProperty as value. I want to be able to generically operate on the properties. i.e. if I want to get the max and min values of a property given its string name I have methods that are completely generic that will pull out the associated AbstactProperty from each element and find the max/min no matter what the type is. so properties although initially declared as PropertyFloat/PropertyString they will be held generically.

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• XAML Multi-Level Binding Source/Path Issue

  - by tpartee

  So I have this issue I've been trying various ways to tackle all day and nothing's catching and working for it. Basically I have a XAML object called ChromeWindow (derived from Window) which has in it's code-behind a DependencyProperty called AppChrome which stores a reference to an associated ApplicationChrome XAML object (derived from UserControl). ApplicationChrome's XAML file has a few x:Name'd objects (a TextBlock and Border for instance) to which I want to bind to from the ChromeWindow's XAML. The root of the ChromeWindow is x:Name'd as 'rootWindow' in the XAML, so I figured one of these bindings would work: {Binding ElementName=rootWindow, Path=AppChrome.CaptionTextBlock.Text, Mode=OneWay} But that complains of a BindingExpression path error such that the property 'CaptionTextBlock' (an x:Name'd TextBlock in AppChrome's XAML) cannot be found on object of type ApplicationChrome So I tried this binding intead: {Binding Source=AppChrome.CaptionTextBlock, Path=Text, Mode=OneWay} And still no luck, this time complaints of a BindingExpression path error again, but this time that it cannot find the 'CaptionTextBlock' property on object of type String I know I'm missing something really simple here, please help! ;D

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• Is it possible to create a C++ factory system that can create an instance of any "registered" object

  - by chrensli

  Hello, I've spent my entire day researching this topic, so it is with some scattered knowledge on the topic that i come to you with this inquiry. Please allow me to describe what I am attempting to accomplish, and maybe you can either suggest a solution to the immediate question, or another way to tackle the problem entirely. I am trying to mimic something related to how XAML files work in WPF, where you are essentially instantiating an object tree from an XML definition. If this is incorrect, please inform. This issue is otherwise unrelated to WPF, C#, or anything managed - I solely mention it because it is a similar concept.. So, I've created an XML parser class already, and generated a node tree based on ObjectNode objects. ObjectNode objects hold a string value called type, and they have an std::vector of child ObjectNode objects. The next step is to instantiate a tree of objects based on the data in the ObjectNode tree. This intermediate ObjectNode tree is needed because the same ObjectNode tree might be instantiated multiple times or delayed as needed. The tree of objects that is being created is such that the nodes in the tree are descendants of a common base class, which for now we can refer to as MyBase. Leaf nodes can be of any type, not necessarily derived from MyBase. To make this more challenging, I will not know what types of MyBase derived objects might be involved, so I need to allow for new types to be registered with the factory. I am aware of boost's factory. Their docs have an interesting little design paragraph on this page: o We may want a factory that takes some arguments that are forwarded to the constructor, o we will probably want to use smart pointers, o we may want several member functions to create different kinds of objects, o we might not necessarily need a polymorphic base class for the objects, o as we will see, we do not need a factory base class at all, o we might want to just call the constructor - without #new# to create an object on the stack, and o finally we might want to use customized memory management. I might not be understanding this all correctly, but that seems to state that what I'm trying to do can be accomplished with boost's factory. But all the examples I've located, seem to describe factories where all objects are derived from a base type. Any guidance on this would be greatly appreciated. Thanks for your time!

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• [C++] Question on Virtual Methods

  - by bobber205

  IF both methods are declared as virtual, shouldn't both instances of Method1() that are called be the derived class's Method1()? I am seeing BASE then DERIVED called each time. I am doing some review for an interview and I want to make sure I have this straight. xD class BaseClass { public: virtual void Method1() { cout << "Method 1 BASE" << endl; } }; class DerClass: public BaseClass { public: virtual void Method1() { cout << "Method 1 DERVIED" << endl; } }; DerClass myClass; ((BaseClass)myClass).Method1(); myClass.Method1(); Method 1 BASE Method 1 DERVIED

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• Question on Virtual Methods

  - by bobber205

  IF both methods are declared as virtual, shouldn't both instances of Method1() that are called be the derived class's Method1()? I am seeing BASE then DERIVED called each time. I am doing some review for an interview and I want to make sure I have this straight. xD class BaseClass { public: virtual void Method1() { cout << "Method 1 BASE" << endl; } }; class DerClass: public BaseClass { public: virtual void Method1() { cout << "Method 1 DERVIED" << endl; } }; DerClass myClass; ((BaseClass)myClass).Method1(); myClass.Method1(); Method 1 BASE Method 1 DERVIED

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• Composite pattern in C++ problem

  - by annouk

  Hello! I have to work with an application in C++ similar to a phone book: the class Agenda with an STL list of Contacts.Regarding the contacts hierarchy,there is a base-class named Contact(an abstract one),and the derived classes Friend and Acquaintance(the types of contact). These classes have,for instance, a virtual method called getName,which returns the name of the contact. Now I must implement the Composite pattern by adding another type of contact,Company(being derived from Contact),which also contains a collection of Contacts(an STL list as well),that can be either of the "leaf" type(Friends or Acquaintances),or they can be Companies as well. Therefore,Company is the Compound type. The question is: how and where can I implement an STL find_if to search the contact with a given name(via getName function or suggest me smth else) both among the "leaf"-type Contact and inside the Company collection? In other words,how do I traverse the tree in order to find possible matches there too,using an uniform function definition? I hope I was pretty clear...

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• indexing question

  - by user522962

  I have a table w/ 3 columns: name, phone, date. I have 3 indexes: 1 on phone, 1 on date and 1 on phone and date. I have the following statement: SELECT * FROM ( SELECT * FROM people WHERE phone IS NOT NULL ORDER BY date DESC) as t GROUP BY phone Basically, I want to get all unique phone numbers ordered by date. This table has about 2.5 million rows but takes forever to execute....are my indexes right? UPDATE: My EXPLAIN statement comes back with 2 rows: 1 for primary table and 1 for derived table. It says I am using temporary and using filesort for my primary table. For my derived table, it says my possible keys are (phone), and (phone, date) but it is using filesort.

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• Strange C++ thread function invocation

  - by Tony

  I have the following: class DThread { virtual void run()=0; _beginthreadex(NULL,0,tfunc,this,0,&m_UIThreadID); // class itself being passed as param to thread function... static unsigned int __stdcall tfunc(void* thisptr) { static_cast<DThread*>(thisptr)->run(); return 0; } //other stuff } The run function is implemented in a derived class. Why is the function that's being called in the thread being called through a cast this pointer? Is this good practise? Can't it just be called directly? The actual function needing to run is in the derived class. My question is

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• Pass Variables In Inheritance (Obj - C)

  - by Marmik Shah

  I working on a project in Obj-C where i have a base class (ViewController) and a Derived Class (MultiPlayer). Now i have declared certain variables and properties in the base class. My properties are getting accessed from the derived class but im not able to access the variables (int,char and bool type). I'm completely new to Obj-C so i have no clue whats wrong. I have used the data types which are used in C and C++. Is there some specific way to declare variables in Obj-C?? If so, How? Here are my files ViewController.h #import <UIKit/UIKit.h> @interface ViewController : UIViewController @property (weak,nonatomic) IBOutlet UIImageView* backGroungImage; @property (strong,nonatomic) IBOutlet UIImageView *blockView1; @property (strong,nonatomic) IBOutlet UIImageView *blockView2; @property (strong,nonatomic) IBOutlet UIImageView *blockView3; @property (strong,nonatomic) IBOutlet UIImageView *blockView4; @property (strong,nonatomic) IBOutlet UIImageView *blockView5; @property (strong,nonatomic) IBOutlet UIImageView *blockView6; @property (strong,nonatomic) IBOutlet UIImageView *blockView7; @property (strong,nonatomic) IBOutlet UIImageView *blockView8; @property (strong,nonatomic) IBOutlet UIImageView *blockView9; @property (strong,nonatomic) UIImage *x; @property (strong,nonatomic) UIImage *O; @property (strong,nonatomic) IBOutlet UIImageView* back1; @property (strong,nonatomic) IBOutlet UIImageView* back2; @end ViewController.m #import "ViewController.h" @interface ViewController () @end @implementation ViewController int chooseTheBackground = 0; int movesToDecideXorO = 0; int winningArrayX[3]; int winningArrayO[3]; int blocksTotal[9] = {8,3,4,1,5,9,6,7,2}; int checkIfContentInBlocks[9] = {0,0,0,0,0,0,0,0,0}; char determineContentInBlocks[9] = {' ',' ',' ',' ',' ',' ',' ',' ',' '}; bool player1Win = false; bool player2Win = false; bool playerWin = false; bool computerWin = false; - (void)viewDidLoad { [super viewDidLoad]; if(chooseTheBackground==0) { UIImage* backImage = [UIImage imageNamed:@"MainBack1.png"]; _backGroungImage.image=backImage; } if(chooseTheBackground==1) { UIImage* backImage = [UIImage imageNamed:@"MainBack2.png"]; _backGroungImage.image=backImage; } } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } @end I am not able to use the above declared variables in my derived classes!

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• Determine an object's class returned by a factory method (Error: function does not take 1 arguments

  - by tzippy

  I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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• Should I share UI for objects that use common fields?

  - by wb

  I have a parent class that holds all of the fields that are common between all device types. From that, I have a few derived classes that each hold their unique fields. Say I have device type "Switch" and "Transformer". Both derived classes only have 2-3 of their own unique fields. When doing the UI design (windows forms) in this case. Should I create two separate forms for each device type or create a user control with all fields that are shared among all devices? Thank you.

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