我是相对新的C ++,虽然我有在Java中的一点经验。试图接近到下面的问题(这是一个更大的任务的一部分,从我的大学)
class myCustomer :public Customer {/.../}
class myFlight:public Flight {/.../}
class myEmployee :public Employee {/.../}
class myPlane :public Plane {/.../}
所以,客户是一个接口,并myCustomer与实现派生类中,这同样适用于其他地区。(我必须使用这种方式)
随后此(排序的),用于飞行公司数据的基础上的API;
class MyImplementation{
//I want to link id's to an object so i can call object pointer using a given id
map <string,myCustomer*> customers_map;
map <string,myEmployee*> employees_map;
map <string,myReservation*> reservations_map;
map <string,myPlane*> planes_map;
map <string,myFlight*> flights_map;
...
//must implement this function
virtual Customer* addCustomer(string full_name, int priority){
if(!customers_loaded){
load_customers();
}
auto curr_customer = new myCustomer(id,full_name,priority);
customers_map.insert(pair<string,myCustomer*>(id,curr_customer));
}
void load_customers(){
vector<string> parameters;
string line;
fstream customers_file;
customers_file.open(CUSTOMER_INFO_PATH,fstream::out);
//check if null is returned
if (!customers_file.is_open()) {
throw "Error:cannot open employees file";
}
//iterate over lines
while(getline(customers_file,line)){
//just a function to split a line from file to a vector
parameters=splitLine(line,SPLITTER);
try{
customer_from_string(parameters);
}catch(...){
//could not load current object
cout << "Could not load customer "<< parameters[0] <<
"(line number:"<< lineNumber << ")" <<endl;
continue;
}
}
customers_file.close();
}
void customer_from_string(vector<string> parameters){
string id = parameters[0];
string name = parameters[1];
int priority = stoi(parameters [2];
auto curr_customer = new myCustomer(id,name,priority);
customers_map.insert(pair<string,myCustomer*>(id,curr_customer));
}
void employee_from_string(vector<string>& parameters,
map<string, string>& toLink) {
//get parameters
string employee_id = parameters[0];
Jobs job = string_to_job(parameters[1]);
int seniority = stoi(parameters[2]);
int year = stoi(parameters[3]);
string employer_id = parameters[4];
//check if employee_id is legal
if (employer_id.empty()) {
throw "Employer ID cannot be an empty argument";
}
auto curr_employee = new myEmployee(employee_id, job, seniority,year);
//add to employee map
employees_map.insert(pair<string, myEmployee *>(employee_id, curr_employee));
}
/** more code**/
所以我试着从一个文本文件中读取参数,并创建使用匹配像customer_from_string功能指定的对象,employee_from_string,我必须这样做对其他类(飞机,预订机票...)每个人都有自己的构造不同参数个数。这些类之间的唯一联系就是它们都实现具有功能的ID接口:
virtual string getID() = 0;
试图避免下面的代码重复(所以我不会创建为每个对象负荷功能):
void load_employees() {
/** same code as load_customers**/
//iterate over lines
while (getline(employees_file, line)) {
//as before
parameters = splitLine(line, SPLITTER);
try {
/*the only change - it has different implementation than customer_from_string*/
employee_from_string(parameters);
} catch (...) {
/** print error **/
}
}
/** as before **/
}
我了解我必须解决这个使用工厂设计模式(因为我需要动态地创建在文本文件中列出的对象,他们每个我打开程序时加载到数据库),所以我想过实现以下:
class Factory {
virtual void create(vector<string>& parameters,
map<string,Factory*>&id_map,/*..more parameters*/)=0;
}
而让负载方法决定哪些对象来创建(也许发送焦炭用作标识符),使用上述方法创建,让每类实现工厂接口和比使用创建函数,如下所示:
//Implementation for customer
void create(vector<string>& parameters,map<Factory *, string>&
toLink,map<string,Factory*>& id_map){
string id = parameters[0];
string name = parameters[1];
int priority = stoi(parameters [parameters.size()-1]);
auto curr_customer = new myCustomer(id,name,priority);
id_map.insert(pair<string,Factory *>(id,curr_customer));
}
所以,我想我需要改变映射到
map <string,Factory *> objectName_map;
现在即时通讯有点卡住因为地图holdes一个指向工厂对象,我想使用的地图ID的做到以下几点:
virtual Customer* getCustomer(string id){ //must implement this function
if(!customers_loaded){
load('Customers');
}
return customers_map.find(id)->second;
}
我不能调用任何内部函数为每个对象后,可以说:
void setEmployer(Employee* employer){//...//}
由于地图是拿着工厂*。我试图保持的地图,因为它们是不可能,但使用它们的创造功能,因为它不能在myCustomer *对象转换为厂*。林有点失去了,试图找到解决方案在线,但没有运气,但我觉得实现这个错误IM。预先感谢任何帮助!
*编辑后使问题更清晰
所以,你真正需要的是一个“工厂”模板:
template<typename T>
pair<string, shared_ptr<T>>
from_string_vector(const vector<string>& parameters);
有明确的专业化喜欢:
template<>
pair<string, shared_ptr<myCustomer>>
from_string_vector(const vector<string>& parameters) {
string id = parameters[0];
string name = parameters[1];
int priority = stoi(parameters [2]);
return make_pair(id, make_shared<myCustomer>(
id, name, priority));
}
和通用功能,如:
template<typename T>
void load_database(map<string, shared_ptr<T>>& objectMap,
const string& filename) {
vector<string> parameters;
string line;
ifstream file(filename);
while (getline(file, line)) {
parameters = splitLine(line, SPLITTER);
objectMap.insert(from_string_vector<T>(parameters));
}
}
然后调用这个函数6次,所有的地图和文件名?