Pass template parameter to function which calls member functions

Question

I want to pass a vector of type that is only known during compile time to a function which will pass it to other functions (to push elements depending on the type of vector).

How should i do it to ensure that the compiler does not throw the error:

test.cpp: In instantiation of 'void funcPushInt(std::vector) [with C = classB]': test.cpp:28:20: required from 'void checkType(std::vector) [with A = classB]' test.cpp:53:16: required from here test.cpp:38:3: error: no matching function for call to 'std::vector::push_back(int&)' vec.push_back(i); ^

#include <typeinfo>
#include <vector>
using namespace std;

class classB
{
    private:
        int i;
    public:
        B()
        {
            i = 0;
        }
}

template <class A>
void checkType(vector<A>);
template <class C>
void funcPushInt(vector<C>);
template <class B>
void funcPushClassB(vector<B>);

template <class A>
void checkType(vector<A> vec)
{
  // check type of vec
  if(typeid(vec) == typeid(vector<int>)) 
    funcPushInt(vec);
  else if(typeid(vec) == typeid(vector<classB>))
    funcPushClassB(vec);
}

template <class C>
void funcPushInt(vector<C> vec)
{
  // push int
  int i = 1;
  vec.push_back(i);
}

template <class B>
void funcPushClassB(vector<B> vec)
{
  // error as it can't push float to vector<int>
  classB objB;
  vec.push_back(objB);
}

int main()
{
    // empty vec of classB type
  vector<classB> vec;
  checkType(vec);
}

I'm more concerned about all the template functions with no declared return types and by-value parameters upon which local changes mean nothing to the caller upon return — WhozCraig
– WhozCraig, Commented Feb 10, 2015 at 5:51
Basically: 1) check type of vector 2) depending on type, create object of that type and push it in — LockheedL1011
– LockheedL1011, Commented Feb 10, 2015 at 6:07
Create object how? Are you assuming it is default constructible? — Pradhan
– Pradhan, Commented Feb 10, 2015 at 13:14

R Sahu · Accepted Answer · 2015-02-10 05:56:02Z

2

Your functions don't have a return type. Assuming that is an error of omission, you might as well have two functions.

template <class A>
void checkType(vector<A> vec)
{
    funcPushFloat(vec);
}

void checkType(vector<int> vec)
{
    funcPushInt(vec);
}

answered Feb 10, 2015 at 5:56

R Sahu

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3 Comments

LockheedL1011 Over a year ago

Thanks or the reply, but I want a single checkType function instead of using multiple functions. And yes, i left out the return types

R Sahu Over a year ago

Is there a technical reason why you want a single function?

LockheedL1011 Over a year ago

Not really.. Just for convenience's sake and not having to repeat a bunch of code. I guess i'll have to do it that way then. Thanks R Sahu!

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