I'm writing a simple UWP app and get errors with a pretty basic (I think so) thing.
I want to pass some data between pages:
void BusStat::NewTripPage::CreateTrip_Click( Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e )
{
this->Frame->Navigate( Windows::UI::Xaml::Interop::TypeName( TripPage::typeid ), "sometext" );
}
Which is okay.
Problems occur on second page:
void TripPage::OnNavigatedTo( NavigationEventArgs^ e ) {}
That gives compiler error C2509: OnNavigatedTo': member function not declared in 'BusStat::TripPage'.
And when I declare the function:
void OnNavigatedTo( NavigationEventArgs^ e );
That gives compiler errors C2601 [syntax error] and C2511 ['void BusStat::TripPage::OnNavigatedTo(Windows::UI::Xaml::Navigation::NavigationEventArgs ^)': overloaded member function not found in 'BusStat::TripPage']
I must add that an example shown here: https://learn.microsoft.com/pl-pl/windows/uwp/design/basics/navigate-between-two-pages#3-pass-information-between-pages also won't compile for me because of the same reasons.
Any possible solutions?
In the header file, you should declare the method as follows:
protected:
virtual void OnNavigatedTo(Windows::UI::Xaml::Navigation::NavigationEventArgs^ e) override;
You can see this in the UWP Samples repository, for example here.
Related
This is for windows using MSVC compiler version 14.28.29910:
Libraries built using colcon. This was meant for a ROS2 application but I dont believe ROS has anything to do with it.
I have been stuck on this issue for two days now and I still am at a loss as to what is going on. Any help will be greatly appreciated.
I have a library that I am statically linking against. Library A. it is built with colcon. Could this be a linking issue or an issue with the fact that I build library A with a certain set of preprocessors and I build library B with a different set of preprocessors that change the Gameobject class to a different version shown below but same function implementations.
ament_auto_add_library(A STATIC
${SOURCES}
${HEADERS}
)
ament_target_dependencies(A ${ALL_DEPENDS})
install(TARGETS
A
EXPORT A_export
LIBRARY DESTINATION lib
RUNTIME DESTINATION bin
)
ament_export_libraries(A_export HAS_LIBRARY_TARGET)
I then link to it from a ros2 package using the standard
target_link_libraries(B A)
I have a object called Gameobject that is defined in library A.
#file --------------------------Gameobject.h
#ifdef InLibraryA
class Gameobject
{
int GetPosx(){return data.x;}
}
#else
class Gameobject
{
int GetPosx(){return data.x;}
}
#endif
#file --------------------------MoveGameObject.h
class MoveGameObject
{
int MoveGObj_inline(Gameobject* g)
{
return g->getPosx();
}
int MoveGObj(Gameobject* g);
}
#file --------------------------MoveGameObject.cpp
int MoveGameObject::MoveGObj(Gameobject* g)
{
return g->getPosx();
}
Now in library B , I do this within a subscription callback
SomeCallback()
{
Gameobject* g = GetGObjectFromPool();
MoveGameObject* m= new MoveGameObject();
//this will return NULL value
int posx = m->MoveGObj(g);
//this will be fine because it was inlined?
int possx = m->MoveGObj_inline(g);
}
You will see that I get null when calling the function that was NOT inlined for calling the getter function from Gameobject. I dont get null for the inlined function even though they run the exact same code. Note that this only happens to non-inline functions that call Gameobject functions. Does not happen to functions that do not read memory from Gameobject. addingTwoInts() for example works fine Non-inline. There are no errors. It is undefined behavior. Any ideas on what I could be doing wrong for this to happen? The simplified code above is the same as to what is happening in my code, just removed unnecessary details.
I'm been trying to start doing a plug-in for a program called "Euroscope" for quite some time and i still can't do anything. I even read a C++ book and nothing, it's too difficult to start.
The question i'm going to ask is a little bit specific and it's going to be difficult to explain but i'm tired of trying to solve this by my own so here it comes.
I have a class that i imported with a bunch of function prototypes in the header called "EuroscopePlugIn".
My principal .cpp is this:
void CPythonPlugInScreen::meu()
{
//loop over the planes
EuroScopePlugIn::CAircraft ac;
EuroScopePlugIn::CAircraftFlightPlan acfp;
CString str;
CPythonPlugIn object;
for(ac=GetPlugIn()->AircraftSelectFirst();
ac.IsValid();
ac=GetPlugIn()->AircraftSelectNext(ac))
{
EuroScopePlugIn::CAircraftPositionData acpos=ac.GetPosition();
const char *c=ac.GetCallsign();
object.printtofile_simple_char(*c);
object.printtofile_simple_int(ac.GetState());
};
object.printtofile_simple_int(ac.GetVerticalSpeed());
object.printtofile_simple_int(acfp.GetFinalAltitude());
cout<<acfp.GetAlternate();
}
the "printtofile_simple_int" and "printtofile_simple_char" are defined is the class CPythonPlugIn like this:
void printtofile_simple_int(int n){
ofstream textfile;
textfile.open("FP_simple_int.txt");
textfile<<(n);
textfile.close();
So i open the program, load the .dll i created with Build->Solution and it does nothing, the .txt files aren't even created and even the cout produces nothing.
I will give you some of the prototype infos on the header file "EuroScopePlugIn.h" in case you need them to understand my micro program. If you need other,ask me and i'll put it here
//---GetPlugIn-----------------------------------------------------
inline CPlugIn * GetPlugIn ( void )
{
return m_pPlugIn ;
} ;
&
CAircraft AircraftSelectFirst ( void ) const ;
//-----------------------------------------------------------------
// Return :
// An aircraft object instance.
//
// Remark:
// This instance is only valid inside the block you are querying.
// Do not save it to a static place or into a member variables.
// Subsequent use of an invalid extracted route reference may
// cause ES to crash.
//
// Description :
// It selects the first AC in the list.
//-----------------------------------------------------------------
&
int GetFinalAltitude ( void ) const ;
//-----------------------------------------------------------------
// Return :
// The final requested altitude.
//-----------------------------------------------------------------
Please guys i need help to start with the plug-in making, from that point on with a methodology of trial and error i'll be on my way. I'm just finding it extremely hard to start...
Thank you very much for the help
I am new to MFC PROGRAMMING. I use vs 2008, in a Dialog Based App. I want to call bellow function on a button click event...?
When I call like SortList(listboxone); is giving an error that SortList not found...!
Please help me..!!
void SortList(CListBox& templistbox)
{
DWORD_PTR abc;
int a=templistbox.GetCurSel();// Select current Item Index
if(a<templistbox.GetCount()-1)
{
abc = (DWORD_PTR )templistbox.GetItemData(a);
a++;
templistbox.SetItemData(a,(DWORD_PTR) templistbox.GetItemData(templistbox.GetCurSel()));
}
}
Sorry now I changed the function to as above but still gives same error.
You probably are calling the function above the function definition. In C/C++, you need to define the function (or it's prototype at least) before calling the function. Put this:
void SortList(CListBox& templistbox);
at the the top of the source file.
I am just trying to compile a bit bigger project using the Visual Studio 2012 Release Candidate, C++. The project was/is compiled using the VS2010 now. (I am just greedy to get the C++11 things, so I tried. :)
Apart of things that I can explain by myself, the project uses the code like this:
ostringstream ostr;
ostr << "The " __FUNCTION__ "() failed to malloc(" << i << ").";
throw bad_alloc(ostr.str().c_str());
The compiler now complains
error C2248: 'std::bad_alloc::bad_alloc' : cannot access private member declared
in class 'std::bad_alloc'
... which is true. That version of constructor is now private.
What was the reason to make that version of constructor private? Is it recommended by C++11 standard not to use that constructor with the argument?
(I can imagine that if allocation failed, it may cause more problems to try to construct anything new. However, it is only my guess.)
Thanks,
Petr
The C++11 Standard defines bad_alloc as such (18.6.2.1):
class bad_alloc : public exception {
public:
bad_alloc() noexcept;
bad_alloc(const bad_alloc&) noexcept;
bad_alloc& operator=(const bad_alloc&) noexcept;
virtual const char* what() const noexcept;
};
With no constructor that takes a string. A vendor providing such a constructor would make the code using it not portable, as other vendors are not obliged to provide it.
The C++03 standard defines a similar set of constructors, so VS didn't follow this part of the standard even before C++11. MS does try to make VS as standard compliant as possible, so they've probably just used the occasion (new VS, new standard) to fix an incompatibility.
Edit: Now that I've seen VS2012's code, it is also clear why the mentioned constructor is left private, instead of being completely removed: there seems to be only one use of that constructor, in the bad_array_new_length class. So bad_array_new_length is declared a friend in bad_alloc, and can therefore use that private constructor. This dependency could have been avoided if bad_array_new_length just stored the message in the pointer used by what(), but it's not a lot of code anyway.
If you are accustomed to passing a message when you throw a std::bad_alloc, a suitable technique is to define an internal class that derives from std::bad_alloc, and override ‘what’ to supply the appropriate message.
You can make the class public and call the assignment constructor directly, or make a helper function, such as throw_bad_alloc, which takes the parameters (and additional scalar information) and stores them in the internal class.
The message is not formatted until ‘what’ is called. In this way, stack unwinding may have freed some memory so the message can be formatted with the actual reason (memory exhaustion, bad request size, heap corruption, etc.) at the catch site. If formatting fails, simply assign and return a static message.
Trimmed example:
(Tip: The copy constructor can just assign _Message to nullptr, rather than copy the message since the message is formatted on demand. The move constructor, of course can just confiscate it :-).
class internal_bad_alloc: public std::bad_alloc
{
public:
// Default, copy and move constructors....
// Assignment constructor...
explicit internal_bad_alloc(int errno, size_t size, etc...) noexcept:
std::bad_alloc()
{
// Assign data members...
}
virtual ~internal_bad_alloc(void) noexcept
{
// Free _Message data member (if allocated).
}
// Override to format and return the reason:
virtual const char* what(void) const noexcept
{
if (_Message == nullptr)
{
// Format and assign _Message. Assign the default if the
// format fails...
}
return _Message;
}
private:
// Additional scalar data (error code, size, etc.) pass into the
// constructor and used when the message is formatted by 'what'...
mutable char* _Message;
static char _Default[];
}
};
//
// Throw helper(s)...
//
extern void throw_bad_alloc(int errno, size_t size, etc...)
{
throw internal_bad_alloc(errno, size, etc...);
}
VERSION 1
class Doh {
private:
static std::map<const std::string, const Doh*> someMap;
std::string stringValue_;
public:
Doh(std::string str) : stringValue_(str) {
Doh::someMap.insert(
std::make_pair<const std::string,const Doh*>
(this->stringValue_,this)
);
}
}
The above was ok with MSVC 2010 but with MSVC 2008 it fails – and I guess it is because the object is not constructed yet when it is inserted in the map (I got a memory access violation).
So, I tried a delayed insertion, which worked:
VERSION 2
Doh(std::string str) : stringValue_(str) {
boost::thread(&Doh::insertIntoTheStaticMap,this);
}
void insertIntoTheStaticMap() {
boost::this_thread::sleep(boost::posix_time::milliseconds(1000));
Doh::someMap.insert(
std::make_pair<const std::string,const Doh*>
(this->stringValue_,this)
);
}
But as you might be able to guess, my intention is to have the static Doh::someMap as a common lookup dictionary.
VERSION 1 didn’t need any thread-safety because I would create all Doh instances in the same thread – in initialization blocks - which would be called by dynamic initializers before I enter main().
But with VERSION 2, the naïve sleep() is neither graceful nor reliable (not to mention, I might need to lock the map before insertion).
What would be a nice KISS approach?
Only potential issue I see is the initialization of the static member, if there are multiple source files. Try guarding it with a function.
class Doh {
private:
static std::map< std::string, Doh * > &get_map() {
static std::map< std::string, Doh * > someMap;
return someMap; // initialize upon first use
}
std::string stringValue_;
public:
Doh(std::string str) : stringValue_(str) {
get_map().insert(
std::make_pair
(this->stringValue_,this)
);
}
};
In neither version is there any sign of init for stringvalue_ - what does the debugger show you about this key when you hit the map insert in version 1 of the code? How is this field set up, and what is its type?
Running this in the debugger for VS2008 should allow you to narrow down the point of failure into the <map> source, I would have thought.