CODEWITHSUNDEEP
c++namespaces
Chandrahas
Chandrahas

Reputation: 335

Using same namespace in C++ for two classes declared and defined in separate files

I am trying to declare two classes C1 and C2 in files nstest1.h and nstest2.h which are defined in files nstest1.cpp and nstest2.cpp respectively. Both the classes are defined under same namespace.

Following are the files :

//nstest1.h
namespace Mine{
    class C1{
        public:
        void callme();
    };
}

//nstest2.h
namespace Mine {
    class C2 {
        public:
            void callme();
    };
}

//nstest1.cpp
#include<iostream>
#include "nstest1.h"

using namespace std;
using namespace Mine;

void Mine::C1::callme(){
    std::cout << "Please call me " << std::endl;
}

//nstest2.cpp
#include<iostream>
#include "nstest2.h"

using namespace std;
using namespace Mine;

void Mine::C2::callme(){
    std::cout << "Please call me too" << std::endl ;
}

Following file tries to use this classes using namespace Mine.

//nstest.cpp
#include<iostream>
#include "nstest1.h"
#include "nstest2.h"

using namespace std;
using namespace Mine;

int main(){
    Mine::C1 c1;
    Mine::C2 c2;
    c1.callme();
    c2.callme();
    return 0;
}

When I compile using command "g++ nstest.cpp", I get following error :

/tmp/cc2y4zc6.o: In function `main':
nstest.cpp:(.text+0x10): undefined reference to `Mine::C1::callme()'
nstest.cpp:(.text+0x1c): undefined reference to `Mine::C2::callme()'
collect2: error: ld returned 1 exit status

If the definitions are moved to the declaration files (nstest1.h and nstest2.h), it works fine. Not sure whats happening here. Am I missing something ? Thanks in advance :) .

Upvotes: 0

Views: 3513

Answers (2)

m8mble
m8mble

Reputation: 1545

Your problem happens at link time. Your headers are fine. But you should compile the other cpp files aswell.

Upvotes: 1

R Sahu
R Sahu

Reputation: 206567

You need to include the other .cpp files when building the program.

Option 1: Compile all the files and build the executable in one command

g++ nstest.cpp nstest1.cpp nstest2.cpp -o nstest

Option 2: Compile each file separately and then build the executable after that

g++ -c nstext1.cpp
g++ -c nstest2.cpp
g++ -c nstest.cpp
g++ nstest.o nstest1.o nstext2.o -o nstest

Upvotes: 3

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