CODEWITHSUNDEEP
c++templatesvisual-c++inheritance
Chris Wilson
Chris Wilson

Reputation: 31

Receiving an error based on template class and it's child class's function calls

1>main.obj : error LNK2019: unresolved external symbol "public: virtual bool __thiscall LinkedSortedList<int>::getfirst(int &)" (?getfirst@?$LinkedSortedList@H@@UAE_NAAH@Z) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol "public: virtual void __thiscall LinkedSortedList<int>::clear(void)" (?clear@?$LinkedSortedList@H@@UAEXXZ) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol "public: virtual void __thiscall LinkedSortedList<int>::print(void)const " (?print@?$LinkedSortedList@H@@UBEXXZ) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol "public: virtual bool __thiscall LinkedSortedList<int>::insert(int)" (?insert@?$LinkedSortedList@H@@UAE_NH@Z) referenced in function _main
1>main.obj : error LNK2001: unresolved external symbol "public: virtual bool __thiscall LinkedSortedList<int>::find(int)const " (?find@?$LinkedSortedList@H@@UBE_NH@Z)
1>main.obj : error LNK2001: unresolved external symbol "public: virtual int __thiscall LinkedSortedList<int>::size(void)const " (?size@?$LinkedSortedList@H@@UBEHXZ)
1>c:\users\chris\documents\visual studio 2010\Projects\lab0\Debug\lab0.exe : fatal error LNK1120: 6 unresolved externals

This is what I recieve when trying to compile my code. I've narrowed it down to (i believe) this section of code here:

#ifndef _LinkedSortedListClass_
#define _LinkedSortedListClass_


    #include "LinkedNode.h"
    #include "SortedList.h"

    template <class Elm>
    class LinkedSortedList: public SortedList<int> {    
    public:

        void clear();

        bool insert(Elm newvalue);

        bool getfirst(Elm &returnvalue);

        void print() const;

        bool find(Elm searchvalue) const;

        int size() const;

    private:
            LinkedNode<Elm>* head;
    };

    #endif

This is the child class of the SortedList, which is this, in case it's needed..

#ifndef _SortedListClass_
#define _SortedListClass_

template <class Elm> class SortedList {
public:

  // -------------------------------------------------------------------
  // Pure virtual functions -- you must implement each of the following
  // functions in your implementation:
  // -------------------------------------------------------------------

  // Clear the list.  Free any dynamic storage.
  virtual void clear() = 0;          

  // Insert a value into the list.  Return true if successful, false
  // if failure.
  virtual bool insert(Elm newvalue) = 0;

  // Get AND DELETE the first element of the list, placing it into the
  // return variable "value".  If the list is empty, return false, otherwise
  // return true.
  virtual bool getfirst(Elm &returnvalue) = 0;

  // Print out the entire list to cout.  Print an appropriate message
  // if the list is empty.  Note:  the "const" keyword indicates that
  // this function cannot change the contents of the list.
  virtual void print() const = 0;

  // Check to see if "value" is in the list.  If it is found in the list,
  // return true, otherwise return false.  Like print(), this function is
  // declared with the "const" keyword, and so cannot change the contents
  // of the list.
  virtual bool find(Elm searchvalue) const = 0;

  // Return the number of items in the list
  virtual int size() const = 0;
};

#endif

Thanks so much for any help; our last class taught us nothing of inheritance, but this is project #1 for this class, without being taught inheritance here either, so this is all touch and go for me, despite what I managed to look up on Google.

Upvotes: 0

Views: 599

Answers (2)

Philipp Neufeld
Philipp Neufeld

Reputation: 1103

Maybe it helps if you placed the definitions of your functions in your header file. This makes it easier for the compiler to resolve these external symbols.

I hope this will help.

Regards, Philinator

Upvotes: 0

John Zwinck
John Zwinck

Reputation: 249133

Your methods aren't defined. So the linker is complaining because it can't link to their definitions.

Upvotes: 1

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