CODEWITHSUNDEEP
c++qt
bustedware
bustedware

Reputation: 324

Undefined reference to template member function

I'm using Qt 5.5.1 and am trying to use a template class for some properties in my application but on build I'm getting undefined references to each type of that template class.

This build used to work in MSVC++ 2015 but after switching to Qt I believe I might not be following some syntactical convention?

Here is my header file:

#include <array>
#include <string>
using namespace std;

template <const int SIZE>
class Property
{
public:
    Property(const array<pair<int, string>, SIZE>* properties);
    ~Property();
    string getPropertyValue(int code);
private:
    const array<pair<int, string>, SIZE>* mProperties;
};

Here is my source file:

#include "Property.h"

template <const int SIZE>
Property<SIZE>::Property(const array<pair<int, string>, SIZE>* properties)
{
    mProperties = properties;
}

template <const int SIZE>
Property<SIZE>::~Property() {}

template <const int SIZE>
string Property<SIZE>::getPropertyValue(int code)
{
    for (int i = 0; i < SIZE; i++) 
    {
        if( code == mProperties[0][i].first )
        {
             return mProperties[0][i].second;
        }
    }

    string("no value found");
}

Here is my implementation:

#include <iostream>
#include "Property.h"
using namespace std;

const int arrSize = 1;
const array<pair<int, string>, arrSize> arrValues{
    make_pair(0x02, string("String Value"))
};

int main()
{
    Property<arrSize>* properties = new Property<arrSize>(&arrValues);
    cout << properties->getPropertyValue(2) << endl;
    return 0;
}

Here is my build output:

undefined reference to `Property<1>::Property(std::array<std::pair<int, std::string>, 1u> const*)'
undefined reference to `Property<1>::getPropertyValue(int)'

I want to have multiple properties and the compiler complains about each different size Property<2>:: ... Property<44>:: ... etc... Any help would be greatly appreciated. Also, what is a better way to do code/value lookup like this?

Thanks!

Upvotes: 1

Views: 1147

Answers (1)

Josh
Josh

Reputation: 73

Templates need to only be defined within header files, this is why you are getting an undefined reference. I was able to run this successfully once I moved the source template code file into the header file.

Upvotes: 2

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