Conflicting declaration of objects. Need Solution Please

The Light and Fan are two different vendor classes and they are not derived from any base class.
I am trying to implement the Command design pattern but with generic implementation, so it should work in future with any new vendor class like Door, Window etc without much change in client code. I have thought about a Factory method but it will not work because it needs a Base class.

It is not an assignment; I am trying to learn the design patterns.

Light *myobj;
Fan *myobj;
int choice;
cout<<"Select Light (1): ";
cout<<"Select Fan (2): ";
cin>>choice;

if (choice ==1){
Light *myobj = new Light();
}
if (choice ==2){
Fan *myobj = new Fan();
}

FlipUpCommand switchUp(*myobj);




Error:conflicting declaration 'Fan*myobj'

You have four different declarations of myobj. What's wrong with a base class?

I am assuming that I do not have the right to change the vendor class and each vendor is providing its own class of implementation.

Give those "each vendor" class objects different names!

Quote:

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Originally Posted by VictorN

Give those "each vendor" class objects different names!

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Ok. then I have to put FlipUpCommand switchUp(*myobj); statement in each 'IF' which I do not want to do.

Quote:

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Originally Posted by fsixteen

Ok. then I have to put FlipUpCommand switchUp(*myobj); statement in each 'IF' which I do not want to do.

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Then you could do something like

Code:

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void *myobj = NULL;
Light *myLight;
Fan *myFan;

int choice;
cout<<"Select Light (1): ";
cout<<"Select Fan (2): ";
cin>>choice;

if (choice ==1)
{
        Light *myLight = new Light();
        myobj = (void*)myLight;
}
if (choice ==2)
{
      Fan *myFan = new Fan();
      myobj = (void*)myFan;
}
FlipUpCommand switchUp(*myobj);

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Note that in such a case your FlipUpCommand class had to know what type of object (Light or Fan) was actually passed in and cast the void* pointer to corresponding class.

Quote:

---

Originally Posted by VictorN

Then you could do something like

Code:

---

void *myobj = NULL;
Light *myLight;
Fan *myFan;

int choice;
cout<<"Select Light (1): ";
cout<<"Select Fan (2): ";
cin>>choice;

if (choice ==1)
{
        Light *myLight = new Light();
        myobj = (void*)myLight;
}
if (choice ==2)
{
      Fan *myFan = new Fan();
      myobj = (void*)myFan;
}
FlipUpCommand switchUp(*myobj);

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Note that in such a case your FlipUpCommand class had to know what type of object (Light or Fan) was actually passed in and cast the void* pointer to corresponding class.

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Error: `void*' is not a pointer-to-object type

Quote:

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Originally Posted by fsixteen

Error: `void*' is not a pointer-to-object type

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What line produces this error?

Quote:

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Originally Posted by VictorN

What line produces this error?

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FlipUpCommand switchUp(*myobj);

Quote:

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Originally Posted by fsixteen

FlipUpCommand switchUp(*myobj);

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How did you declare it (FlipUpCommand ctor)?
In the suggested design (if your Fan and Light classes do not have a common base class) it should be declared as

Code:

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FlipUpCommand (void*);

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Please, edit your post adding Code tags around your code snippets!
Otherwise your code is absolutely unreadable! :(

Quote:

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Originally Posted by VictorN

Please, edit your post adding Code tags around your code snippets!
Otherwise your code is absolutely unreadable! :(

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trying code edit

Quote:

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Code:

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#include <iostream>
#include <typeinfo>

using namespace std;

/*the Command interface*/
class Command
{
public:
template <typename t>
virtual void execute(t obj)=0;
template <typename T>
friend bool operator ==( T left, T right );
};
template <typename T>
bool operator==( T left, T right ){
return (left == right);
}

/*Receiver class*/
class Light {

public:
Light() { }

void turnOn()
{
cout << "The light is on" << endl;
}

void turnOff()
{
cout << "The light is off" << endl;
}
};

class Fan {

public:
Fan() { }

void turnOn()
{
cout << "The Fan is on" << endl;
}

void turnOff()
{
cout << "The Fan is off" << endl;
}
};

/*the Command for turning on the light*/
class FlipUpCommand: public Command
{
public:
template <typename t>
FlipUpCommand(t myobject)

{
if (myobject == theLight){
theLight=myobject;
execute(theLight)
}
if (myobject = theFan){
theFan = myobject;
execute(theLight)
}

}

template <typename t>
virtual void execute(t obj)
{

obj.turnOn();
}

public:
Light theLight;
Fan theFan;
};

class FlipDownCommand: public Command
{
public:
template <typename t>
FlipUpCommand(t myobject)

{
if (myobject == theLight){
theLight=myobject;
execute(theLight)
}
if (myobject = theFan){
theFan = myobject;
execute(theLight)
}

}

template <typename t>
virtual void execute(t obj)
{

obj.turnOff();
}

public:
Light theLight;
Fan theFan;
};



class Switch {
public:
Switch(Command& flipUpCmd, Command& flipDownCmd)
:flipUpCommand(flipUpCmd),flipDownCommand(flipDownCmd)
{

}

void flipUp()
{
flipUpCommand.execute();
}

void flipDown()
{
flipDownCommand.execute();
}

public:
Command& flipUpCommand;
Command& flipDownCommand;
};


/*The test class or client*/

int main()
{


void *myobj = NULL;
Light *myLight;
Fan *myFan;

int choice;
cout<<"Select Light (1): ";
cout<<"Select Fan (2): ";
cin>>choice;

if (choice ==1)
{
Light *myLight = new Light();
myobj = (void*)myLight;
}
if (choice ==2)
{
Fan *myFan = new Fan();
myobj = (void*)myFan;
}

FlipUpCommand switchUp(*myobj);


FlipUpCommand switchUp(*myobj);
FlipDownCommand switchDown(*myobj);
Switch s(switchUp, switchDown);



cout<<" ON (1), OFF(2) :";
cin>>choice;
if(choice ==1){
s.flipUp();
}
if(choice==2){
s.flipDown();
}


int stop;
cin>>stop;
}

---

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Why the colors are not appearing in my code ?

Quote:

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Originally Posted by fsixteen

Why the colors are not appearing in my code ?

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You'd better have asked: "Why the code indentations are not appearing in my code ?" :mad:
And the answer would be very simple: just because you put unformatted code between the tags! :thumbd:

Note, that I didn't ask you to repost the code, just to edit the previous post adding code tags!

How to solve this problem.

class FlipUpCommand: public Command
{
public:
template <typename t>
FlipUpCommand(t *obj)
{

}
};

FlipUpCommand switchUp(*myobj);

Error: void is not a pointer to object Type.
I believe I am doing something wrong with FlipUpCommand constructor

Well, I have to tell you again (and it is the last time!):
Please, post properly formatted code with indentations and within Code tags!

And not just a couple of lines but your actual code (or code snippet) that we will be able to compile and test.
Note that the code you have posted in the post#12 has nothing to do with the one in your OP!

Code after edit

Quote:

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Code:

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#include <iostream>
#include <typeinfo>

using namespace std;

/*the Command interface*/
class Command
{
public:
          template <typename t>
          virtual void execute(t obj)=0;

          template <typename T>
          friend bool operator ==( T left, T right );
};

template <typename T>
bool operator==( T left, T right ){
          return (left == right);
                                            }

/*Receiver class*/
class Light {

public:
              Light() { }

              void turnOn() {
               
                  cout << "The light is on" << endl;
                                  }


              void turnOff() {
                cout << "The light is off" << endl;
                                }
};

class Fan {

public:
              Fan() { }

              void turnOn() {

                cout << "The Fan is on" << endl;
                                }

            void turnOff() {

                cout << "The Fan is off" << endl;
                                }
};

/*the Command for turning on the light*/

class FlipUpCommand: public Command {

public:
              template <typename t>
              FlipUpCommand(t myobject) {
                      if (myobject == theLight){
                      theLight=myobject;
                      execute(theLight);
                                                      }
                    if (myobject = theFan){
                    theFan = myobject;
                    execute(theLight);
                                                }

}

              template <typename t>
              virtual void execute(t obj){
              obj.turnOn();
                                                  }

public:
          Light theLight;
          Fan  theFan;
};


class FlipDownCommand: public Command {

public:
                  template <typename t>
                  FlipUpCommand(t myobject){
                      if (myobject == theLight){
                      theLight=myobject;
                      execute(theLight);
                                                }
                    if (myobject = theFan){
                      theFan = myobject;
                      execute(theLight);
                                                  }

                                    }

        template <typename t>
        virtual void execute(t obj) {
              obj.turnOff();
                                            }

public:
      Light theLight;
      Fan  theFan;
};



class Switch {
public:
Switch(Command& flipUpCmd, Command& flipDownCmd):flipUpCommand(flipUpCmd),flipDownCommand(flipDownCmd)
{

}

void flipUp()
{
flipUpCommand.execute();
}

void flipDown()
{
flipDownCommand.execute();
}

public:
Command& flipUpCommand;
Command& flipDownCommand;
};


/*The test class or client*/

int main()
{


void *myobj = NULL;
Light *myLight;
Fan *myFan;

int choice;
cout<<"Select Light (1): ";
cout<<"Select Fan (2): ";
cin>>choice;

  if (choice ==1) {

        Light *myLight = new Light();
        myobj = (void*)myLight;
                      }
    if (choice ==2){
      Fan *myFan = new Fan();
      myobj = (void*)myFan;
                        }

FlipUpCommand switchUp(*myobj);
FlipUpCommand switchUp(*myobj);
FlipDownCommand switchDown(*myobj);
Switch s(switchUp, switchDown);

cout<<" ON (1), OFF(2) :";
cin>>choice;
    if(choice ==1){
      s.flipUp();
                      }
    if(choice==2){
      s.flipDown();
                    }


getch();
}

---

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Well, I put your code into file temp.cpp and tried to compile it in VS2010:

Code:

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  temp.cpp
d:\2010 projects\temp\temp\temp.cpp(11): error C2898: 'void Command::execute(t)' : member function templates cannot be virtual
d:\2010 projects\temp\temp\temp.cpp(74): error C2898: 'void FlipUpCommand::execute(t)' : member function templates cannot be virtual
d:\2010 projects\temp\temp\temp.cpp(88): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
d:\2010 projects\temp\temp\temp.cpp(101): error C2898: 'void FlipDownCommand::execute(t)' : member function templates cannot be virtual
d:\2010 projects\temp\temp\temp.cpp(121): error C2780: 'void Command::execute(t)' : expects 1 arguments - 0 provided
          d:\2010 projects\temp\temp\temp.cpp(11) : see declaration of 'Command::execute'
d:\2010 projects\temp\temp\temp.cpp(126): error C2780: 'void Command::execute(t)' : expects 1 arguments - 0 provided
          d:\2010 projects\temp\temp\temp.cpp(11) : see declaration of 'Command::execute'
d:\2010 projects\temp\temp\temp.cpp(160): error C2100: illegal indirection
d:\2010 projects\temp\temp\temp.cpp(161): error C2100: illegal indirection
d:\2010 projects\temp\temp\temp.cpp(161): error C2374: 'switchUp' : redefinition; multiple initialization
          d:\2010 projects\temp\temp\temp.cpp(160) : see declaration of 'switchUp'
d:\2010 projects\temp\temp\temp.cpp(162): error C2100: illegal indirection
d:\2010 projects\temp\temp\temp.cpp(162): error C2664: 'FlipDownCommand::FlipDownCommand(const FlipDownCommand &)' : cannot convert parameter 1 from 'void *' to 'const FlipDownCommand &'
          Reason: cannot convert from 'void *' to 'const FlipDownCommand'
          No constructor could take the source type, or constructor overload resolution was ambiguous
d:\2010 projects\temp\temp\temp.cpp(175): error C3861: 'getch': identifier not found
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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So, please, fix these errors, then we could talk about your further design.