C++ Builder Pattern with Forward Declaration [closed] - c++

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I recently got stuck in a situation. In the first version, everything is implemented in header file and it works fine. In the second version when i tried to separate implementation from header declarations, I got many errors. In the below lines, i m going to demonstrate problem. Thanks in advance..
First Version (it works fine!)
cameravalue.h
#ifndef CAMERAVALUE_H
#define CAMERAVALUE_H
#include <string>
class CameraValue
{
private:
class CameraProperties
{
private:
CameraProperties()
: mId(-1),
mName(),
mAddress(),
mExposure(),
mFocus()
{}
int mId;
std::string mName;
std::string mAddress;
std::string mExposure;
long long mFocus;
friend class CameraValue;
friend class CameraBuilder;
};
public:
class CameraBuilder
{
public:
CameraBuilder(int id)
{
mProperties.mId = id;
}
CameraBuilder& setName(std::string& name)
{
mProperties.mName = name;
return *this;
}
CameraBuilder& setAddress(std::string& adress)
{
mProperties.mAddress = adress;
return *this;
}
CameraBuilder& setExposure(std::string& exposure)
{
mProperties.mExposure = exposure;
return *this;
}
CameraBuilder& setFocus(int focus)
{
mProperties.mFocus = focus;
return *this;
}
CameraValue build()
{
return CameraValue(mProperties);
}
private:
CameraProperties mProperties;
};
private:
CameraValue(const CameraProperties& properties)
:mProperties(properties)
{}
CameraProperties mProperties;
};
#endif // CAMERAVALUE_H
main.cpp
#include "cameravalue.h"
#include <iostream>
int main(int argc, char *argv[])
{
CameraValue cm = CameraValue::CameraBuilder(1).setName(std::string("Huseyin")).build();
return 0;
}
Second Version (Don't work)
cameravalue.h
#ifndef CAMERAVALUE_H
#define CAMERAVALUE_H
#include <string>
class CameraValue
{
private:
class CameraProperties;
public:
class CameraBuilder;
private:
CameraValue(const CameraProperties& properties);
CameraProperties mProperties;
};
#endif // CAMERAVALUE_H
cameravalue.cpp
#include "cameravalue.h"
#include <string>
class CameraValue::CameraProperties
{
private:
CameraProperties()
: mId(-1),
mName(),
mAddress(),
mExposure(),
mFocus()
{}
int mId;
std::string mName;
std::string mAddress;
std::string mExposure;
long long mFocus;
friend class CameraValue;
friend class CameraBuilder;
};
class CameraValue::CameraBuilder
{
public:
CameraBuilder(int id)
{
mProperties.mId = id;
}
CameraBuilder& setName(std::string& name)
{
mProperties.mName = name;
return *this;
}
CameraBuilder& setAddress(std::string& adress)
{
mProperties.mAddress = adress;
return *this;
}
CameraBuilder& setExposure(std::string& exposure)
{
mProperties.mExposure = exposure;
return *this;
}
CameraBuilder& setFocus(int focus)
{
mProperties.mFocus = focus;
return *this;
}
CameraValue build()
{
return CameraValue(mProperties);
}
private:
CameraProperties mProperties;
};
CameraValue::CameraValue(const CameraProperties& properties)
: mProperties(properties)
{}
main.cpp
#include "cameravalue.h"
#include <iostream>
int main(int argc, char *argv[])
{
CameraValue cm = CameraValue::CameraBuilder(1).setName(std::string("Huseyin")).build();
return 0;
}
Compile Errors
cameravalue.cpp
c:\users\huseyin\documents\builderpattern\cameravalue.h(20) : error
C2079: 'CameraValue::mProperties' uses undefined class
'CameraValue::CameraProperties' ..\BuilderPattern\cameravalue.cpp(74)
: error C2440: 'initializing' : cannot convert from 'const
CameraValue::CameraProperties' to 'int'
No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
..\BuilderPattern\cameravalue.cpp(74) : error C2439:
'CameraValue::mProperties' : member could not be initialized
c:\users\huseyin\documents\builderpattern\cameravalue.h(20) : see declaration of 'CameraValue::mProperties'
c:\users\huseyin\documents\builderpattern\cameravalue.h(20) : error
C2079: 'CameraValue::mProperties' uses undefined class
'CameraValue::CameraProperties' ..\BuilderPattern\main.cpp(9) : error
C2440: '<function-style-cast>' : cannot convert from 'int' to
'CameraValue::CameraBuilder'
Source or target has incomplete type ..\BuilderPattern\main.cpp(9) : error C2228: left of '.setName' must
have class/struct/union ..\BuilderPattern\main.cpp(9) : error C2228:
left of '.build' must have class/struct/union
..\BuilderPattern\main.cpp(9) : error C2512: 'CameraValue' : no
appropriate default constructor available
..\BuilderPattern\main.cpp(10) : error C2039: 'getName' : is not a
member of 'CameraValue'
c:\users\huseyin\documents\builderpattern\cameravalue.h(8) : see declaration of 'CameraValue'

Answer 1

Definition of class CameraBuilder should be visible in main.cpp, so you can't just forward-declare it in cameravalue.h. But you can make the definitions of its member functions out-of-line:
// cameravalue.h
class CameraValue {
class CameraBuilder {
public:
CameraBuilder(int id);
...
};
};
// cameravalue.cpp
CameraValue::CameraBuilder::CameraBuilder(int id) {
...
}