how do you pass an array to a template function? [duplicate] - c++

Question

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Why can templates only be implemented in the header file?
(17 answers)
Closed 8 years ago.
In my main I create an object from a template class, then I call my sort method (template method)
However it get a error in my main.obj file.
error:
LNK2019: unresolved external symbol "public: void __thiscall SelectionSort<int [0]>::IterativeSort(int * const,unsigned int)" ............
Call in main:
SelectionSort<int[]> smallArraySort;
smallArraySort.IterativeSort(smallArray, smallSize);
Header file: SelectionSort.h
template <class T>
class SelectionSort
{
public:
void IterativeSort(T data, unsigned int size);
void RecursiveSort(T data, unsigned int size);
};
sort code: SelectionSort.cpp
#include "SelectionSort.h"
template<class T>
void SelectionSort<T> ::IterativeSort(T data, unsigned int size)
{
int temp = data[0];
int greaterNum = 0
for (unsigned int index = 0; index < size; index++)
{
for (unsigned int inner = index; inner < size; inner++)
{
if (temp>data[inner])
{
greaterNum = temp;
temp = data[inner];
data[inner] = greaterNum;
}
}
}
}

Answer 1

This happens because you implement the methods of the template in a .cpp file where they cannot be seen when they need to be instantiated. In general, templates must be defined in a header file.
To solve the problem, eliminate your SelectionSort.cpp file by moving its definitions into SelectionSort.h.