i am using visual C++ 2010 i m having just one error i want user to enter inputs model and color and then it will pass to a public variable and public member function will access private data members and assign values to it then a public member function will display those values main.when i try to write s1.colr[10] to pass it to fuunction it gives error.
include
using namespace std;
#include<conio.h>
class vehicle
{
private:
int d;
char color[10];
public:
int mdl;
char colr[10];
void get_input(int a,char b[10])
{
d=a ;
color[10]=b[10];
}
void disp()
{
cout<<"Model Number Is:"<<d ;
cout<<"Color Is:"<<color[10];
}
};
int main()
{
vehicle s1;
cout<<"Enter Model Number:";
cin>>s1.mdl;
cout<<"Enter Color:";
cin>>s1.colr[10];
s1.get_input(s1.mdl,s1.colr[10]);
s1.disp();
getch();
}
Use s1.colr insterad of so.colr[10]
cin>>s1.colr[10];
s1.get_input(s1.mdl,s1.colr[10]);
and you code will compile.
Don't use conio.h, #inlude <iostream>.
Live on coliru
Related
I am having troubles incrementing the value of my instance variables. I tried making a method so that for every pet I buy, it will add that much to how many I already have. But when I print dogs variable, it says 0 even though I added 2. I'd appreciate any help. Thanks!
public class myStuff
static int dogs;
static int cats;
public static void main(String[] args) {
myStuff.buy(dogs, 2);
System.out.println(dogs);
}
public static void buy(int pet, int howMany) {
pet = pet + howMany;
}
}
you cant do that in java, since it is pass-by-value
In Java, method parameters are passed by value (which means the value of dogsin your case is passed in the first Place, but never touched). Objects however, are manipulated by reference. So, if you want to increase the number of pets, you could use a class Pet with a value count
public class Pet {
private int count;
public Pet(int count) {
this.count = count;
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
}
If you then pass an instance of Pet to your buy function and increase the count via setCount, the value will be saved.
//MyWrapper.h
#include "arithmetic.h"
#include "mathematics.h"
namespace MyWrapper {
public ref class ClassA
{
public:
ClassA();
~ClassA();
int add(int, int);
private:
MyEngine::Arithmetic *nativeClassA;
}
public ref class ClassB
{
public:
ClassB(ClassA^ arith);
~ClassB();
int pow(int, int);
private:
MyEngine::Mathematics *nativeClassB;
}
}
//MyWrapper.cpp
#include "MyWrapper.h"
My::ClassA::ClassA()
{
nativeClassA = new MyEngine::Arithmetic();
}
My::ClassA::~ClassA()
{
delete nativeClassA;
}
int My::ClassA::add(int a, int b)
{
return nativeClassA->add(a, b);
}
My::ClassB::ClassB(ClassA^ classA)
{
nativeClassB = new MyEngine::Mathematics(classA->nativeClassA); //***Error***
}
My::ClassB::~ClassB()
{
delete nativeClassB;
}
int My::ClassB::pow(int a, int b)
{
int result = nativeClassB->pow(a, b);
return result;
}
Here, Mathematics class need to init with Arithmetic class.
But nativeClassA is private variable in ClassA.
So nativeClassB = new MyEngine::Mathematics(classA->nativeClassA); , it will occurs compile error.
So I changed the nativeClassA to public.
But at that time, nativeClassA will export to c#.
I don't want to export nativeClassA variable to c#.
How can I fix it?
Thanks in advice.
Since you're writing a managed class, you can use all the access modifiers that C# has. This seems like a perfect scenario for internal. (The linked documentation is for C#, but it's the same keyword in C++/CLI.)
typedef struct pt_input_bir
{
PT_BYTE byForm;
union {
PT_BIR *pBIR; ///< Used when byForm = PT_FULLBIR_INPUT */
PT_LONG lSlotNr; ///< Used when byForm = PT_SLOT_INPUT */
PT_BYTE abyReserved[20]; /** For future use */
} InputBIR;
} PT_INPUT_BIR
typedef struct pt_bir {
PT_BIR_HEADER Header;
PT_BYTE Data[1];
} PT_BIR
typedef struct pt_bir_header {
PT_DWORD Length;
PT_BYTE HeaderVersion;
PT_BYTE Type;
PT_WORD FormatOwner;
PT_WORD FormatID;
PT_CHAR Quality;
PT_BYTE Purpose;
PT_DWORD FactorsMask;
} PT_BIR_HEADER
and the C function is
PT_STATUS StoreFinger (
IN PT_CONNECTION hConnection,
IN PT_INPUT_BIR *pTemplate,
OUT PT_LONG *plSlotNr
)
Now I need to do the wrapper for the above C function in C#.
How should I marshal the PT_INPUT_BIR* structure and how should I unmarshal it after return of this function?
Please help me to solve this.
/********************** FOR MORE DETAIL ABOUT THIS QUESTION**************************/
C struct and function are defined in above. pls refer there.
C# Struct :
For C# struct declaration i have maintatined two struct for the one C struct. bcz one is for setting the values and another one id for passing to c function.
C# app struct:
[StructLayout(LayoutKind.Sequential)]//for app
public struct FPINPUTBIR
{
public byte byForm;
public InputBIRType InputBIR;
}
[StructLayout(LayoutKind.Sequential)] // here when i use explicit it throws exception so i removed it.
public struct InputBIRType
{
// [FieldOffset(0)]
public FPBIR pBIR;
//[FieldOffset(0)]
public int lSlotNr;
//[FieldOffset(0)]
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
public byte[] abyReserved;
}
C# wrapper struct:
[StructLayout(LayoutKind.Sequential)]
public struct FP_INPUTBIR
{
public byte byForm;
public IntPtr mIPBIR;
}
[StructLayout(LayoutKind.Explicit, Size = 20, CharSet = CharSet.Ansi)]
public struct Input_BIRType
{
[FieldOffset(0)]
public IntPtr mBIR;
[FieldOffset(0)]
public int lSlotNr;
//[FieldOffset(8)]
//[MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
//public byte[] abyReserved;
}
finally i will copy the value from the C# app struct to wrapper struct before the call the C fun()
2a) C# App Side Code is :
//here mAppMemory is already known value
FPINPUTBIR lfipdata = new FPINPUTBIR();
FPDATA lfpdata = new FPDATA();
lfipdata.byForm = (byte)eFPVerifyBy.FULLBIR_INPUT;
lfipdata.InputBIR = new InputBIRType();
lfipdata.InputBIR.abyReserved = new byte[20];
lfipdata.InputBIR.pBIR.Data = new byte[mAppMemory[listBox2.SelectedIndex].Header.Length];
Array.Copy(mAppMemory[listBox2.SelectedIndex].Data, lfipdata.InputBIR.pBIR.Data, mAppMemory[listBox2.SelectedIndex].Header.Length);
lfipdata.InputBIR.pBIR.Header = mAppMemory[listBox2.SelectedIndex].Header;
Verify(ref lfipdata); //calling from C# APP side to C# wrapper
C# wrapper side:
public int Verify(ref FPINPUTBIR apStoredTemplate )
{
// i passed the args (apStoredTemplate ) but throws exception struct mismatch with C struct.
//here i don't know what should i do.
CDLL.StoreFinger(..,ref apStoredTemplate,.. ); //pls refer the C function above
}
Questions:
Do i really need two C# structures for this.
what should i do inside the C# wrapper function. please remeber i have two C# struct with diff members.
Thanks.
You just need a little extension on what you used in the previous question for PT_BIR. There we marshalled that variable length struct as byte[]. You can use the same code to generate the byte array, and I won't revisit that.
Next you need the union. That is:
[StructLayout(LayoutKind.Explicit, Size = 20)]
public struct PT_INPUT_BIR_UNION
{
[FieldOffset(0)]
public IntPtr pBIR;
[FieldOffset(0)]
public int lSlotNr; // I'm guessing what PT_LONG is
}
No need to declare the reserved part of the union. The size takes care of that.
Then PT_INPUT_BIR is
[StructLayout(LayoutKind.Sequential)]
public struct PT_INPUT_BIR
{
Byte byForm;
PT_INPUT_BIR_UNION InputBirUnion;
}
Then you need to use GCHandle to pin the PT_BIR byte array. Let's keep to the same naming as used at that question, and assume that the PT_BIR is held in a byte[] variable named data.
GCHandle handle = GCHandle.Alloc(data, GCHandleType.Pinned);
try
{
PT_INPUT_BIR inputBir;
inputBir.byForm := ...;
inputBir.InputBirUnion.pBIR = handle.AddrOfPinnedObject();
// now call StoreFinger passing ref inputBir
}
finally
{
handle.Free();
}
When you declare StoreFinger the PT_BIR* parameter should be declared as ref PT_BIR.
Such as mfc, it should add
DECLARE_SERIAL(CGraph)
If I a have a class,
class A
{
int a,b;
};
I can store the value of a and b to a file ,then read it.
So I couldn't understand why DECLARE_SERIAL(CGraph) used.
The DECLARE_SERIAL and IMPLEMENT_SERIAL macros are only necessary for classes derived from CObject that you wish to serialize polymorphically using the framework provided by MFC.
If your class is not derived from CObject and/or you do not wish to use MFC's serialization polymorphically (i.e. via a pointer to CObject), then of course you can implement your own solution as you rightly say.
For example, DECLARE_SERIAL(CMyClass) expands to the following code that goes in your class declaration
protected:
static CRuntimeClass* __stdcall _GetBaseClass();
public:
static CRuntimeClass classCMyClass;
static CRuntimeClass* __stdcall GetThisClass();
virtual CRuntimeClass* GetRuntimeClass() const;
static CObject* __stdcall CreateObject();
friend CArchive& __stdcall operator>>(CArchive& ar, CMyClass* &pOb);
and IMPLEMENT_SERIAL(CMyClass, CObject, VERSIONABLE_SCHEMA | 1) expands to the following code that goes in the cpp file
CObject* __stdcall CMyClass::CreateObject()
{
return new CMyClass;
}
extern AFX_CLASSINIT _init_CMyClass;
CRuntimeClass* __stdcall CMyClass::_GetBaseClass()
{
return (CObject::GetThisClass());
}
__declspec(selectany) CRuntimeClass CMyClass::classCMyClass =
{
"CMyClass", sizeof(class CMyClass), (0x80000000) | 1,
CMyClass::CreateObject, &CMyClass::_GetBaseClass, 0, &_init_CMyClass
};
CRuntimeClass* __stdcall CMyClass::GetThisClass()
{
return ((CRuntimeClass*)(&CMyClass::classCMyClass));
}
CRuntimeClass* CMyClass::GetRuntimeClass() const
{
return ((CRuntimeClass*)(&CMyClass::classCMyClass));
}
AFX_CLASSINIT _init_CMyClass((CMyClass::GetThisClass()));
CArchive& __stdcall operator>>(CArchive& ar, CMyClass* &pOb)
{
pOb = (CMyClass*) ar.ReadObject((CMyClass::GetThisClass()));
return ar;
}
As it says in MSDN it is also possible to use serialization without using the above macros:
I'm trying to write a wrapper for a very simple std::pair<std::string, float> in C++/CLI but I get the error message: no instance of constructor "std::pair<_Ty1, _Ty2>::pair [with _Ty1=std::string, _Ty2=float]" matches the argument list, argument types are: (std::string, float)
What am I doing wrong and why doesn't std::string match std::string?
#include <msclr\marshal_cppstd.h>
#include <string>
using namespace System;
using namespace System::Runtime::InteropServices;
typedef std::pair<std::string, float> Parameter;
static std::string StringToNative(String^ str)
{
msclr::interop::marshal_context context;
return context.marshal_as<std::string>(str);;
}
public ref class CLIParameter
{
public:
CLIParameter(System::String^ name, float value) : _name(name), _value(value) {};
Parameter toNativeParameter()
{
return Parameter(StringToNative(_name), _value);
}
private:
System::String^ _name;
float _value;
};
int main()
{
CLIParameter^ par = gcnew CLIParameter("test", 1);
}
Your method toNativeParameter() is incorrect. It should be defined as follows:
Parameter toNativeParameter()
{
// copy the floating point value from the managed heap to the local stack
float value = _value;
// create the pair
return std::make_pair(StringToNative(_name), value);
}
Notice that you should use std::make_pair to create the actual pair. In addition, a key step to make this work is copying the floating point value from the managed heap into the local stack. The reason is that native functions such as std::make_pair cannot create native references to an object from the managed (garbage collected) heap i.e. a member of a managed class.