我试图将两个对象相加，即使它们包含相同的变量。我通过重载 operator += 来执行此操作，但我无法设法返回在 unionOfBag 函数内创建的新临时对象。我只得到相同的默认对象，但没有添加。
类文件:
#pragma once
#include "BagInterface.h"
#include <iostream>
#include <vector>
using namespace std;
static const int DEFAULT_CAPACITY = 20;
template <class ItemType>
class ArrayBag : public BagInterface<ItemType> {
private:
//ItemType *aptr;
ItemType items[DEFAULT_CAPACITY];
int itemCount;
int maxItems;
int getIndexOf(const ItemType &target, int searchIndex) const;
int countFrequency(const ItemType &target, int searchIndex) const;
public:
ArrayBag();
//ArrayBag(const ArrayBag<ItemType> &aBag);
int getCurrentSize() const;
bool isEmpty() const;
bool add(const ItemType &newEntry);
bool remove(const ItemType &newEntry);
void clear();
bool contains(const ItemType &anEntry) const;
int getFrequencyOf(const ItemType & anEntry) const;
vector<ItemType>toVector() const;
ArrayBag<ItemType> &unionOfBags(const ArrayBag<ItemType> &aBag) const;
ArrayBag<ItemType> intersectionOfBags(const ArrayBag<ItemType> &aBag) const;
ArrayBag<ItemType> differenceOfBags(const ArrayBag<ItemType> &aBag) const;
ArrayBag<ItemType> &operator += (const ArrayBag<ItemType> &aBag);
ItemType &operator [] (int subs);
};
template <class ItemType>
ArrayBag<ItemType>::ArrayBag() {
itemCount = 0;
maxItems = DEFAULT_CAPACITY;
}
//template <class ItemType>
//ArrayBag<ItemType>::ArrayBag(const ArrayBag<ItemType> &aBag) {
//
// this->items = aBag.items;
// this->itemCount = DEFAULT_CAPACITY;
//
//}
template <class ItemType>
bool ArrayBag<ItemType>::add(const ItemType &newEntry) {
bool hasRoomToAdd = (itemCount < maxItems);
if (hasRoomToAdd) {
items[itemCount] = newEntry;
itemCount++;
}
return hasRoomToAdd;
}
template <class ItemType>
vector<ItemType> ArrayBag<ItemType>::toVector() const {
vector<ItemType> bagContents;
for (int i = 0; i < itemCount; i++) {
bagContents.push_back(items[i]);
}
return bagContents;
}
template<class ItemType>
int ArrayBag<ItemType>::getCurrentSize() const {
return itemCount;
}
template<class ItemType>
bool ArrayBag<ItemType>::isEmpty() const {
return itemCount == 0;
}
template <class ItemType>
bool ArrayBag<ItemType>::contains(const ItemType &anEntry) const {
/*return getFrecuencyOf(target) > 0;*/
bool found = false;
int curIndex = 0;
while (!found && (curIndex < itemCount)) {
if (anEntry == items[curIndex])
found = true;
curIndex++;
}
return found;
}
template<class ItemType>
bool ArrayBag<ItemType>::remove(const ItemType &anEntry) {
int locatedIndex = getIndexOf(anEntry, 0);
bool canRemoveItem = !isEmpty() && (locatedIndex > -1);
if (canRemoveItem) {
itemCount--;
items[locatedIndex] = items[itemCount];
}
return canRemoveItem;
}
template <class ItemType>
void ArrayBag<ItemType>::clear() {
itemCount = 0;
}
template <class ItemType>
int ArrayBag <ItemType>::getIndexOf(const ItemType &target, int searchIndex) const {
int result = -1;
if (searchIndex < itemCount) {
if (items[searchIndex] == target)
result = searchIndex;
else
result = getIndexOf(target, searchIndex + 1);
}
return result;
}
template <class ItemType>
int ArrayBag<ItemType>::getFrequencyOf(const ItemType &anEntry) const {
return countFrequency(anEntry, 0);
}
template <class ItemType>
int ArrayBag<ItemType>::countFrequency(const ItemType &target, int searchIndex) const {
int frequency = 0;
if (searchIndex < itemCount) {
if (items[searchIndex] == target)
frequency = 1 + countFrequency(target, searchIndex + 1);
else
frequency = countFrequency(target, searchIndex + 1);
}
return frequency;
}
//
//template<class ItemType>
//ItemType &ArrayBag<ItemType>::operator [](int subs) {
//
// return aptr[subs];
//
//}
template<class ItemType>
ArrayBag<ItemType> &ArrayBag<ItemType>::operator +=(const ArrayBag<ItemType> &aBag) {
this->itemCount = aBag.itemCount;
for (int i = 0; i < aBag.itemCount; i++) {
this->items[i] += aBag.items[i];
this->itemCount++;
}
return(*this);
}
template<class ItemType>
ArrayBag<ItemType> &ArrayBag<ItemType>::unionOfBags(const ArrayBag<ItemType> &aBag) const{
ArrayBag<ItemType> newBag;
newBag += aBag;
//for (int i = 0; i < aBag.getCurrentSize(); i++) {
// newBag.items[i] += aBag.items[i];
//}
return newBag;
}
template<class ItemType>
ArrayBag<ItemType> ArrayBag<ItemType>::intersectionOfBags(const ArrayBag<ItemType> &aBag) const {
}
template<class ItemType>
ArrayBag<ItemType> ArrayBag<ItemType>::differenceOfBags(const ArrayBag<ItemType> &aBag) const {
}
主要.CPP
#include<iostream>
#include<string>
#include"ArrayBag.h"
using namespace std;
void displayBag(ArrayBag<string> & bag){
cout << "The bag contains " << bag.getCurrentSize()
<< " items:" << endl;
vector<string>bagItems = bag.toVector();
int numberofEntries = (int)bagItems.size();
for (int i = 0; i < numberofEntries; i++)
{
cout << bagItems[i] << " ";
}
cout << endl << endl;
}
void bagTester(ArrayBag<string> & bag)
{
cout << "isEmpty: returns " << bag.isEmpty()
<< "; should be 1 (true)" << endl;
displayBag(bag);
string items[] = { "one", "two", "three", "four", "five", "one" };
cout << "Add 6 items to the bag: " << endl;
for (int i = 0; i < 6; i++)
{
bag.add(items[i]);
}
displayBag(bag);
cout << "isEmpty: returns " << bag.isEmpty()
<< "; should be o (false)" << endl;
cout << "getCurrentSize: returns " << bag.getCurrentSize()
<< "; should be 6" << endl;
cout << "Try to add another entry: add(\"extra\") returns "
<< bag.add("extra") << endl;
}
int main()
{
ArrayBag<string> bag1;
ArrayBag<string> bag2;
ArrayBag<string> newBag;
bag2.add("a");
bag2.add("b");
bag2.add("c");
bag2.add("d");
bagTester(bag1);
bag1.unionOfBags(bag2);
newBag = bag1;
displayBag(newBag);
cout << "All done!" << endl;
return 0;
}
最佳答案
您正在通过引用返回本地创建的对象。这是一个很大的不不。当函数结束时，所有本地对象都将被销毁。由于您从已销毁的对象返回引用，该引用指的是什么？
如果你想返回一个局部变量的对象，你需要按值返回它。
关于c++ - c++ 将两个对象相加，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29309247/