Partial template specialization only for a single function

I've a template where I want to use a pointer type or an instance type as the template parameter. An Example:

class FOO {};

class ItemGetter {
    virtual FOO * GetItem(int index) = 0;
};

template<class T>
class ArrayContainer : public ItemGetter {
    T *array;
    ArrayContainer(T * array) {
        this->array = array;
    }

    /*
     * A lot of other functions.
     * I want to write them only once
     * ....
     */

    /* If the T Parameter is an instance Type */
    FOO * GetItem(int index) {
        return &this->array[index];
    }
    /* If the T Parameter is an pointer Type */
    FOO * GetItem(int index) {
        return this->array[index];
    }
};

void usage() {
  FOO fooArray[100];
  FOO * fooPointerArray[100];

  auto bar1 = ArrayContainer<FOO>(fooArray);
  auto bar2 = ArrayContainer<FOO*>(fooPointerArray);
}

How can I specialize the GetItem() function for the pointer and the instance variant (without writing all the other functions twice)?