Question
void f(cli::array<PointF> ^points){
PointF& a = points[0];
// and so on...
}
Compile error at line 2.
.\ndPanel.cpp(52) : error C2440: 'initializing' : cannot convert from 'System::Drawing::PointF' to 'System::Drawing::PointF &'
An object from the gc heap (element of a managed array) cannot be converted to a native reference
What is the managed way to declare a reference variable?
Solution
If you just want to declare a reference to the first PointF in the array then you need to use a tracking reference (%):
void f(cli::array<PointF>^ points)
{
PointF% a = points[0];
}
OTHER TIPS
You need to use the gcroot
template from vcclr.h
file:
These are samples from MSDN:
// mcpp_gcroot.cpp
// compile with: /clr
#include <vcclr.h>
using namespace System;
class CppClass {
public:
gcroot<String^> str; // can use str as if it were String^
CppClass() {}
};
int main() {
CppClass c;
c.str = gcnew String("hello");
Console::WriteLine( c.str ); // no cast required
}
// mcpp_gcroot_2.cpp
// compile with: /clr
// compile with: /clr
#include <vcclr.h>
using namespace System;
struct CppClass {
gcroot<String ^> * str;
CppClass() : str(new gcroot<String ^>) {}
~CppClass() { delete str; }
};
int main() {
CppClass c;
*c.str = gcnew String("hello");
Console::WriteLine( *c.str );
}
// mcpp_gcroot_3.cpp
// compile with: /clr
#include < vcclr.h >
using namespace System;
public value struct V {
String^ str;
};
class Native {
public:
gcroot< V^ > v_handle;
};
int main() {
Native native;
V v;
native.v_handle = v;
native.v_handle->str = "Hello";
Console::WriteLine("String in V: {0}", native.v_handle->str);
}
You will find out more here
And here is your code changed to use gcroot:
void f(cli::array<gcroot<PointF ^>> points){
gcroot<PointF ^> a = points[0];
// and so on... }
Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow