I have a MainForm. It has two child forms.
The program reads in large SEGY files (2gb -> 100gb), appropiate data and read settings are stored through the class system that has a main controller "SEGY.H" & "SEGY.CPP". They a coded in pure C++.
My two child forms are managed. I want to pass a reference for SEGY from the MainForm to each child form when they are required to be shown to the user, obviously to avoid copying large amounts of memory.
I cannot pass a native class by reference to a managed class through the managed classes constructor.
I have tried (code in mainform):
private: SEGY *Segy; //it then gets constructor call when filename is chose
CHILDFORM ^childform1( Segy ); //constructor for 1st child form that needs to be shown
where I have tried the following as constructor arguments in CHILDFORM.H
CHILDFORM(SEGY* &Segy_inputSegyContainer);
CHILDFORM(SEGY* %Segy_inputSegyContainer);
The latter works and runs (%). Debug in MainForm.h on this line shows under Locals that this->Segy points to a SEGY class with correct values. Debug following CHILDFORM constructor through into CHILDFORM.cpp shows the reference gets curropted and Segy_inputSegyContainer points to a curropted class.
Please can you help me.
Passing Unmanaged Class by reference to Managed Class Constructor
JohnWP
I think I may know the anwser. First off you should know the only valid native code in a managed class is a pointer to a unmanaged object. So any way you don't need to pass by refrence, all you have to do is pass a pointer by value. This is completly valid and will avoid copying the whole file.
Try some thing like this:
public ref class MyManaged
{
private:
SEGY* Segy;
public:
MyManaged(SEGY* Segy)
{
this->Segy = Segy;
}
};
Basically just forget passing by refrence, it is not nessasary in this case, so just remove the & and the %. BUT remember, what I just said will only hold true if you use dynamic allocation aka "new" when you first create your SEGYs, although I doubt you are making them on the stack as that would be both very uncommon and idiotic.
good luck, let us know how you made out
Fwank79
Thank you for taking the time to reply to my post. I basically get the following error message in "MainForm.h" when I compile
I have made a simple project that highlights the problem. The thing that makes me so cross about this is I do not feel I am doing anything radical or complicated. I simply want to use the class system to pass by reference to avoid copying memory. I just feel I haven't discovered the syntax yet.
"cannot convert parameter 1 from 'SEGY *' to 'SEGY *&'
An object from the gc heap (member of a managed class) cannot be converted to a native reference"
The simple project that highlights the problem can be downloaded at http:\\www.will-turner.co.uk\microsoftDrivingMeMad.zip
Gus B
CHILDFORM(SEGY* &Segy_inputSegyContainer);
CHILDFORM(SEGY* %Segy_inputSegyContainer);
Why not SEGY*
JDCAMP
My test number 1:
class Test1
{
public:
Test1(int n) : data(n)
{
}
int GetData(){return data;}
private:
int data;
};
ref class Test2
{
public:
Test2(Test1& t) : test1(t)
{
}
void Print()
{
Console::WriteLine(test1.GetData().ToString());
}
private:
Test1& test1;
};
int main(array<System::String ^> ^args)
{
Test1 t1(5);
Test2 t2(t1);
t2.Print();
return 0;
}
Test number 2:
class Test1
{
public:
Test1(int n) : data(n)
{
}
int GetData(){return data;}
private:
int data;
};
ref class Test2
{
public:
Test2(Test1* t) : test1(t)
{
}
void Print()
{
Console::WriteLine(test1->GetData().ToString());
}
private:
Test1* test1;
};
int main(array<System::String ^> ^args)
{
Test1 t1(5);
Test2 t2(&t1);
t2.Print();
return 0;
}
Both versions successfully compile and run. What is your code exactly and what problem do you have