C++ - static vector of pointers causes undefined reference

[marystew]

I'm trying to create a function below in my CreateReport class called load() that copies all the records (data) from my graduate.dat file into my static vector of Record pointers called primaryCollection. I created a Record class with variables that make up each Record, and in my `load()` function in `createReport.cc` I attempted to read each line in the file, create a Record object with each line, add it to my vector, and then print everything in primaryCollection.

The problem is every time I attempt to use primaryCollection, I keep getting the error:

	CreateReport.o: In function `CreateReport::load()':
	CreateReport.cc:(.text+0x2ac): undefined reference to `CreateReport::primaryCollection'
	CreateReport.cc:(.text+0x31d): undefined reference to `CreateReport::primaryCollection'
	CreateReport.cc:(.text+0x32f): undefined reference to `CreateReport::primaryCollection'

I get 3 undefined references for the 3 times I mention primaryCollection in createReport.cc. I'm not sure what's causing these undefined references. I don't know if this is relevant to my problem, but CreateReport is also an abstract class and has a few subclasses called ReportOne, ReportTwo, etc.

primaryCollection is supposed to be a static vector of Record pointers and I'm also not allowed to use std::map for this task.

I would appreciate any help with this issue.

My graduate.dat file is formatted like below in the format < year province degree >

2000 AB Bachelor's
2005 AB Bachelor's
2005 MB College

Each line basically represents a Record. So the first record here is 2000 AB Bachelor's

Record.h

	#ifndef RECORD_H
	#define RECORD_H

		#include <iostream>
		#include <string>

		class Record{
		  public:
				Record(int = 0, string = "", string = "");
				~Record();
			
			private:
				int year;
				string province;
				string degree;
		};
		#endif 

Record.cc

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

	Record::Record(int i1, string s1, string s2) : year(i1), province(s1), degree(s2){}

	Record::~Record(){}

CreateReport.h

	#ifndef CREATEREPORT_H
	#define CREATEREPORT_H

	#include <iostream>
	#include <fstream>
	#include <string>
	#include <vector>
	#include <iterator>
	#include <algorithm>
	#include <cstdlib>

	#include "Record.h"

	class CreateReport{
	  public:
		CreateReport();
		static void load();
	  
	  protected:
		static vector<Record*> primaryCollection; //STL vector of record pointers
	  
	};
	#endif 

CreateReport.cc

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

	#include "CreateReport.h"

	CreateReport::CreateReport(){ 
	}

	void CreateReport::load(){
		int year;
		string province, degree;

		ostream_iterator<Record*> outItr(cout);

		ifstream infile("graduate.dat", ios::in); 

		if (!infile) {
			cout << "Error: could not open file" << endl;
			exit(1);
		}

		while (infile >> year >> province >> degree) { //as long as were not at end of file
			Record* record = new Record(year, province, degree); //create Record object with this data
			primaryCollection->push_back(record); //undefined reference
		}
	  
		cout<<endl<<"List of Records:"<<endl;
		copy(primaryCollection->begin(), primaryCollection->end(), outItr); //2 undefined references
	}[

[marystew]

I tried adding the line vector<Record*> CreateReport::primaryCollection; above my constructor, outside of the functions in CreateReport.cc but that changed the errors to:

	CreateReport.cc:13:34: error: conflicting declaration ‘std::vector<Record*> CreateReport::primaryCollection’
	 vector<Record*> CreateReport::primaryCollection;
									  ^~~~~~~~~~~~~~~~~
	In file included from CreateReport.cc:5:0:
	CreateReport.h:23:33: note: previous declaration as ‘std::vector<Record*>* CreateReport::primaryCollection’
		static std::vector<Record*>* primaryCollection; //STL vector of record pointers
									 ^~~~~~~~~~~~~~~~~
	CreateReport.cc:13:34: error: declaration of ‘std::vector<Record*>* CreateReport::primaryCollection’ outside of class is not definition [-fpermissive]
	 vector<Record*> CreateReport::primaryCollection;

Again, I would really appreciate any help with this problem. It's really frustrating as I need to test my code but can't due to this one issue with using primaryCollection.

[coder777]

Why do you want primaryCollection? It seems there is no good reason.

However you need to define (not declare) a static variable outside the class:

	#include "CreateReport.h"

	vector<Record*> CreateReport::primaryCollection; //STL vector of record pointers

	CreateReport::CreateReport(){ 
	}