Als ik mijn code compileer voor een gelinkte lijst, krijg ik een heleboel ongedefinieerde referentiefouten. De code staat hieronder. Ik heb deze beide verklaringen samengesteld:
g++ test.cpp
evenals
g++ LinearNode.h LinearNode.cpp LinkedList.h LinkedList.cpp test.cpp
Ik begrijp echt niet waarom ik deze fouten krijg, omdat ik echt roestig ben met klassen in C++. Ik kan echt wat hulp gebruiken.
LinearNode.h:
#ifndef LINEARNODE_H
#define LINEARNODE_H
#include<iostream>
using namespace std;
class LinearNode
{
public:
//Constructor for the LinearNode class that takes no arguments
LinearNode();
//Constructor for the LinearNode class that takes the element as an argument
LinearNode(int el);
//returns the next node in the set.
LinearNode* getNext();
//returns the previous node in the set
LinearNode* getPrevious();
//sets the next element in the set
void setNext(LinearNode* node);
//sets the previous element in the set
void setPrevious(LinearNode* node);
//sets the element of the node
void setElement(int el);
//gets the element of the node
int getElement();
private:
LinearNode* next;
LinearNode* previous;
int element;
};//ends the LinearNode class
#endif
LinearNode.cpp:
#ifndef LINEARNODE_cpp
#define LINEARNODE_cpp
#include<iostream>
#include"LinearNode.h"
using namespace std;
//Constructor for LinearNode, sets next and element to initialized states
LinearNode::LinearNode()
{
next = NULL;
element = 0;
}//ends LinearNode default constructor
//Constructor for LinearNode takes an element as argument.
LinearNode::LinearNode(int el)
{
next = NULL;
previous = NULL;
element = 0;
}//ends LinearNode constructor
//returns the next element in the structure
LinearNode* LinearNode::getNext()
{
return next;
}//ends getNext function
//returns previous element in structure
LinearNode* LinearNode::getPrevious()
{
return previous;
}//ends getPrevious function
//sets the next variable for the node
void LinearNode::setNext(LinearNode* node)
{
next = node;
}//ends the setNext function
//sets previous for the node
void LinearNode::setPrevious(LinearNode* node)
{
previous = node;
}//ends the setPrevious function
//returns element of the node
int LinearNode::getElement()
{
return element;
}//ends the getelement function
//sets the element of the node
void LinearNode::setElement(int el)
{
element = el;
}//ends the setElement function
#endif
LinkedList.h:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
#include<iostream>
#include"LinearNode.h"
using namespace std;
class LinkedList
{
public:
LinkedList();
void add(int element);
int removie (int element);
private:
int count;
LinearNode *contents;
};//ends the class linked list
#endif
LinkedList.cpp:
#ifndef LINKEDLIST_CPP
#define LINKEDLIST_CPP
#include<iostream>
#include"LinearNode.h"
#include"LinkedList.h"
using namespace std;
//linkedlist constructor for an empty linked list
LinkedList::LinkedList()
{
count = 0;
contents = NULL;
}//ends the constructor
//adds an element to the front of the linked list
void LinkedList::add(int element)
{
int found = 0, current = 0;
while( (found == 0) && (current !=count) )
{
if (contents.getElement() == element)
found = 1;
else
{
contents = contents.getNext();
current++;
}//ends the else statement
}//ends the while loop
if (found == 0)
{
LinearNode node = new LinearNode(element);
node.setNext(contents);
contents.setPrevious(node);
count++;
}//ends the found == 0 if statment
}//ends the add function
//this function removes one element from the linked list.
int LinearNode::remove(int element)
{
int found = 0;
if (count == 0)
cout << "The list is empty" << endl;
else
{
if (contents.getElement() == element)
{
result = contents.getElement();
contents = contents.getNext();
}//ends the contents.getElement() == element
else
{
previous = contents;
current = contents.getNext();
for (int index = 0; ( (index < count) && (found == 0) )index++)
if (current.getElement() = element)
found = 1;
else
{
previous = current;
current = current.getNext();
}//ends the else statement
if (found == 0)
cout << "The element is not in the list" << endl;
else
{
result = current.getElement();
previous.setNext(current.getNext());
}//ends else statement
}//ends the else stamtement
count--;
}//ends the else statement of count == 0
return result;
}//ends the remove function
#endif
test.cpp:
#include<iostream>
#include"LinearNode.h"
#include"LinkedList.h"
using namespace std;
int main()
{
LinearNode node1, node2, node3, move;
LinkedList list;
node1.setElement(1);
node2.setElement(2);
node3.setElement(3);
}
Antwoord 1, autoriteit 100%
- Meestal zijn header guards voor header-bestanden (d.w.z.
.h
) niet voor bronbestanden (d.w.z..cpp
). - Neem de benodigde standaard headers en naamruimten op in bronbestanden.
LinearNode.h:
#ifndef LINEARNODE_H
#define LINEARNODE_H
class LinearNode
{
// .....
};
#endif
LinearNode.cpp:
#include "LinearNode.h"
#include <iostream>
using namespace std;
// And now the definitions
LinkedList.h:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
class LinearNode; // Forward Declaration
class LinkedList
{
// ...
};
#endif
LinkedList.cpp
#include "LinearNode.h"
#include "LinkedList.h"
#include <iostream>
using namespace std;
// Definitions
test.cppis het bronbestand is in orde. Merk op dat header-bestanden nooit worden gecompileerd. Ervan uitgaande dat alle bestanden zich in een enkele map bevinden –
g++ LinearNode.cpp LinkedList.cpp test.cpp -o exe.out
Antwoord 2, autoriteit 21%
g++ test.cpp LinearNode.cpp LinkedList.cpp -o test
Antwoord 3, autoriteit 12%
Ik kreeg deze foutmelding omdat mijn cpp-bestanden niet zijn toegevoegd aan het bestand CMakeLists.txt
Antwoord 4, autoriteit 8%
Een andere manier om deze fout te krijgen is door per ongeluk de definitie van iets in een anonieme naamruimte te schrijven:
foo.h:
namespace foo {
void bar();
}
foo.cc:
namespace foo {
namespace { // wrong
void bar() { cout << "hello"; };
}
}
other.cc-bestand:
#include "foo.h"
void baz() {
foo::bar();
}
Antwoord 5, autoriteit 4%
Ik had dit probleem toen ik vergat het nieuwe .h/.c-bestand dat ik had gemaakt toe te voegen aan het mesonrecept, dus dit is slechts een vriendelijke herinnering.
Antwoord 6
Probeer de constructor en destructors te verwijderen, het werkt voor mij….