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friend function: member function of another class giving error if defined before

santoshkb (9)
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#include<iostream>

using namespace std;

class test;

class sampletest
{
        public:
                void getainb(test & x);
               
};

void sampletest::getainb(test & x)
                {
                        cout<<"In sampletest:getainb="<<x.a<<endl;
                }

class test
{
        int a;
        public:
        int geta() {return a;}
        void seta(int x) { a = x;}
        friend void sampletest::getainb(test & x);
};


main()
{
        test t;
        t.seta(23);


                sampletest s;
                s.getainb(t);

}

giving error:
class.cpp: In method `void sampletest::getainb(test &)':
class.cpp:14: invalid use of undefined type `class test'
class.cpp:6: forward declaration of `class test'


But if i move defination of getainb after class test
it works fine.


trying to understand why its giving error.




working code below.
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class test;


class sampletest
{
        public:
                void getainb(test & x);
        
};


class test
{
        int a;
        public:
        int geta() {return a;}
        void seta(int x) { a = x;}
        friend void sampletest::getainb(test & x);
};

void sampletest::getainb(test & x)
{
        cout<<"In sampletest:getainb="<<x.a<<endl;
}

main()
{
        test t;
        t.seta(23);


                sampletest s;
                s.getainb(t);

}



Is it because to acess members compiler needs defination information prior, forward declaration should it not work for this,

Request for your inputs to clear my doubt
Last edited on
kooth (746)
I think it's because the compiler needs to know more about class test than just the forward reference.
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