[当我尝试遍历列表以搜索特定节点时，出现此错误-线程1：EXC_BAD_ACCESS（代码= 1，地址= 0x0）。我从头开始编写List类。这是我的List类，也是我为支持它而编写的所有其他类。
struct ItemInfo{
double Itemprice = 0;
int Itemamount = 0;
};
class List;
class Iterator;
class Node
{
public:
Node(map<string, ItemInfo> temp, string element);
private:
string name;
map<string, ItemInfo> items;
Node* next;
Node* previous;
friend class List;
friend class Iterator;
};
class List
{
public:
List();
void push_back(map<string, ItemInfo> temp, string element);
void insert(Iterator iter, map<string, ItemInfo> temp, string element);
Iterator erase(Iterator iter);
Iterator begin();
Iterator end();
private:
Node* first;
Node* last;
friend class Iterator;
};
class Iterator
{
public:
Iterator();
string get() const;
map<string, ItemInfo> get_map() const;
void next();
void previous();
bool equals(Iterator other) const;
private:
Node* position;
List* container;
friend class List;
};
Node::Node(map<string, ItemInfo> temp, string element )
{
this->name = element;
this->items = temp;
next = nullptr;
}
List::List()
{
first = nullptr;
last = nullptr;
}
void List::push_back(map<string, ItemInfo> temp, string element)
{
Node* new_node = new Node(temp, element);
if (last == nullptr) // List is empty
{
first = new_node;
last = new_node;
}
else
{
new_node->previous = last;
last->next = new_node;
last = new_node;
}
}
void List::insert(Iterator iter, map<string, ItemInfo> temp, string element)
{
if (iter.position == nullptr)
{
push_back(temp, element);
return;
}
Node* after = iter.position;
Node* before = after->previous;
Node* new_node = new Node(temp, element);
new_node->previous = before;
new_node->next = after;
after->previous = new_node;
if (before == nullptr) // Insert at beginning
{
first = new_node;
}
else
{
before->next = new_node;
}
}
Iterator List::erase(Iterator iter)
{
Node* remove = iter.position;
Node* before = remove->previous;
Node* after = remove->next;
if (remove == first)
{
first = after;
}
else
{
before->next = after;
}
if (remove == last)
{
last = before;
}
else
{
after->previous = before;
}
delete remove;
Iterator r;
r.position = after;
r.container = this;
return r;
}
Iterator List::begin()
{
Iterator iter;
iter.position = first;
iter.container = this;
return iter;
}
Iterator List::end()
{
Iterator iter;
iter.position = nullptr;
iter.container = this;
return iter;
}
Iterator::Iterator()
{
position = nullptr;
container = nullptr;
}
string Iterator::get() const
{
return position->name;
}
map<string, ItemInfo> Iterator::get_map() const{
return position->items;
}
void Iterator::next()
{
position = position->next;
}
void Iterator::previous()
{
if (position == nullptr)
{
position = container->last;
}
else
{
position = position->previous;
}
}
bool Iterator::equals(Iterator other) const
{
return position == other.position;
}
而且我还有另一个班级可以帮助我填写此列表，
class inventory
{
public:
//constructor to read frmo file
inventory();
//function to add items in map
void iter();
//last store item entered
void viewInventory();
//get list
List get_list();
private:
List stores;
};
inventory::inventory(){
//read from file function
ifstream read;
string line;
string::size_type idex = 4;
string temp;
int count = 0;
ItemInfo enter;
map<string, ItemInfo> tempMap;
read.open("/Users/vibhorsagar/Desktop/CovidProject/CovidProject/walmartList.txt");
if(!read.is_open()){
cout<<"Error"<<endl;
}else {
while (!read.eof()){
while(getline(read, line)){
stringstream in(line);
while(getline(in, line, '-') && count < 3){
if(count == 0){
temp = line;
}
else if(count == 1){
try{
enter.Itemprice = stod(line, &idex);
} catch(std::invalid_argument){
continue;
}
}
else if(count == 2){
enter.Itemamount = stoi(line);
}
count++;
}
tempMap[temp] = enter;
count = 0;
}
}
stores.push_back(tempMap, "Walmart");
}
}
void inventory::viewInventory(){
cout<<"1) View all stores"<<endl;
cout<<"2) Specific store"<<endl;
int choice = 0;
cin >> choice;
switch(choice){
case 1:{
Iterator iterList = stores.begin();
while (!iterList.equals(stores.end())){
cout<< "Store: "<< iterList.get()<<endl;
for(auto IterMap = iterList.get_map().begin(); IterMap != iterList.get_map().end(); IterMap++){
cout<<"Item: "<< IterMap->first<<endl;
cout<<"Item Price: "<< IterMap->second.Itemprice<<endl;
cout<<"Item Amount: "<< IterMap->second.Itemamount<<endl;
//getting Thread 1: EXC_BAD_ACCESS (code=1, address=0x0)
}
iterList.next();
}
}
case 2:{
string sName;
cout<<"Enter store name"<<endl;
cin>>sName;
Iterator iter = stores.begin();
while( !iter.equals(stores.end())){
if(iter.get() == sName){
cout<< "Store: "<< iter.get()<<endl;
auto iterMap = iter.get_map().begin(); // Thread 1: EXC_BAD_ACCESS (code=1, address=0x0)
while ( iterMap != iter.get_map().end()){
cout<< "Item: "<< iterMap->first<<endl;
cout<< "Item Price: "<< iterMap->second.Itemprice<<endl;
cout<< "Item Amount: "<< iterMap->second.Itemamount<<endl;
iterMap++;
}
}
iter.next();
}
}
}
}
List inventory::get_list(){
return stores;
}
此类基本上是打开一个文本文件并读取其内容并相应地填充列表。我的文本文件包含以下内容-
Marketside Butter Lettuce Salad - 2.98 - 200
Marketside Classic Iceberg Salad - 2.64 - 400
Green Bell Pepper - 0.58 - 1000
Cauliflower - 2.97 - 30
Whole Carrots - 0.92 - 200
因此，库存类的构造函数读取此文件后，便将这些项目放置在地图中，例如
map<string, ItemInfo> tempMap;
//then after reading the first line the map should fill up like this
tempMap[Cauliflower] = (2.97, 30)
从文件中读取并填充列表很正常，但是当我尝试在搜索功能中访问并遍历列表时，出现此错误线程1：EXC_BAD_ACCESS（代码= 1，地址= 0x0）。
这里是我的搜索功能
void SearchItem(string itemName){
inventory inven;
Iterator iter = inven.get_list().begin();
map<string, ItemInfo>::iterator ItemIter ;
for( iter = inven.get_list().begin(); !iter.equals(inven.get_list().end()); iter.next()){
for( ItemIter = iter.get_map().begin(); ItemIter != iter.get_map().end(); ItemIter++){ //Thread 1: EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
if(ItemIter->first == itemName){
cout<<"Item found"<<endl;
cout<<"Item in store: "<< iter.get().StoreName<<endl;
cout<<"Item name: "<< ItemIter->first<<endl;
cout<<"Item price: "<< ItemIter->second.Itemprice<<endl;
cout<<"Item amount in store: "<< ItemIter->second.Itemamount<<endl;
}
else {
cout<<"Item not found in any store"<<endl;
}
}
}
}
这是我的主要功能
int main(){
int n;
inventory check;
cout<<"1. Employee"<<endl;
cout<<"2. Customer"<<endl;
cin>>n;
switch(n){
case 1:{
cout<<"EMPLOYEE"<<endl;
cout<<"View Inventory?(Y/N)"<<endl;
char choice;
cin>>choice;
if(choice == 'y' || choice == 'Y' ){
check.viewInventory();
}
}
case 2:{
cout<<"CUSTOMER"<<endl;
cout<<"Choose one option"<<endl;
cout<<"1. Search by Item name\n"<<"2. Search by Item Price\n"<<"3. Search by Item amount"<<endl;
int choice =0;
cin>>choice;
switch(choice){
case 1:{
cout<<"Search Item"<<endl;
string iName;
getline(cin.ignore(), iName);
SearchItem(iName); // getting Thread 1: EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
cout<<"Sort from lowest to highest?"<<endl;
}
case 2:{
cout<<"Search Price"<<endl;
double price;
cin>>price;
SearchItem(price);
}
}
}
}
return 0;
}
这是我现在拥有的。如果有人可以帮助我，我将不胜感激。
iter.get_map()按值返回地图的副本；两个调用返回两个不同的对象。而且，这些对象是临时对象，在表达式末尾被销毁。 ItemIter成为一个悬空的迭代器-迭代器已损坏的容器。任何使用它的尝试都表现出不确定的行为。