我有两个问题。 1.我是否使用最有效的容器来容纳[double，object *]？ 2.如果Map是我应该使用的选择，那么一旦它在地图中，我是如何访问被指向的对象的？我试图在函数printMap（）中打印地图，没有任何运气。试过多种变化。
void printMap() { //How do i verify what's in my map??!!!!!!!!!!!!!!!!!!!!!!!!
for (it = cDatabase.begin(); it != cDatabase.end(); it++)
{
double temp = 0;
temp = it->first;
cout << "Key: " << it->first << endl;
cout << cDatabase[it->first]->getFirstName();
}
}
提前致谢
埃里克
PS：我包含了整个.cpp文件。
//Erik Plachta
//Purpose: Creating a Customer Relations Management system. Should be able to create employees and customers that can we stored within a database.
#include<fstream> //for customer database
#include<map> //for customer database
#include<sstream> //for customer database
#include<stdlib.h> //for customer database
#include <iostream>
using namespace std;
///////////////////////////////////////////////////////////////////////////////
/////EMPLOYEE///////////EMPLOYEE////////////EMPLOYEE/////////EMPLOYEE//////////
///////////////////////////////////////////////////////////////////////////////
class Employee {
string firstName, lastName, password, username; //used to create unique sessions for each user. Login info
bool manager; //If manager, will have spec privlages within the app.
int sessionTime; //used to record login/logoff time.
public:
Employee(string FN, string LN, string pass, string userN) { //first name, last name and pass
setName(FN, LN);
setPassword(pass);
setUsername(userN);
}
string getName() {
string fullName = firstName + " " + lastName;
return fullName;
}
bool confirmPassword(string pass) { //used to test if true or false without giving program the password back.
bool status = false;
if (pass == password) {
status = true;
}
return status;
}
bool confirmUsername(string userN) {
bool status = false;
if (userN == username) {
status = true;
}
return status;
}
private:
void setName(string FN, string LN) {
firstName = FN;
lastName = LN;}
void setPassword (string pass) {
password = pass;
}
void setUsername(string userN) {
username = userN;
}
};
void printEmployee(Employee employee) { //this is confirming the password entered was the same in the database. there will be a private database holding user login info
bool status;
cout <<"Name: " << employee.getName() << endl;
status = employee.confirmPassword("123456");
cout << "Password test: " << status << endl;
status = employee.confirmUsername("EPlachta");
cout << "Username test: " << status << endl;
}
///////////////////////////////////////////////////////////////////////////////
///CUSTOMER////////////CUSTOMER/////////CUSTOMER/////CUSTOMER//////CUSTOMER////
///////////////////////////////////////////////////////////////////////////////
class Customer {
string firstName, lastName, phoneNumber, eMail;
double customerNumber;
public:
Customer (string FN, string LN, string phoneN, string EM, double customerNum) {
setName(FN, LN);
setPhoneNumber(phoneN);
setEmail(EM);
setCustomerNumber(customerNum);
}
string getFirstName() {
return firstName;
}
string getLastName() {
return lastName;
}
string getPhoneNumber() {
return phoneNumber;
}
string getEmailAddress(){
return eMail;
}
double getCustomerNumber() {
return customerNumber;
}
void printCustomer() {
cout << "First Name: " << getFirstName() << endl;
cout << "lastName: " << getLastName() << endl;
cout << "Email: " << getEmailAddress() << endl;
cout << "PhoneNumber: " << getPhoneNumber() << endl;
cout <<"CustomerNumber: "<< getCustomerNumber() << endl;
}
private:
void setName(string FN, string LN) {
firstName = FN;
lastName = LN;
}
void setPhoneNumber(string phoneN) {
phoneNumber = phoneN;
}
void setEmail(string EM) {
eMail = EM;
}
void setCustomerNumber(double customerNum) {
customerNumber = customerNum;
}
} ;
//print customer is uptop here for now. Will be put into it's own class
///////////////////////////////////////////////////////////////////////////////
///CUSTOMER DATABASE///////////////CUSTOMER DATABASE///////CUSTOMER DATABASE///
///////////////////////////////////////////////////////////////////////////////
class CustomerDatabase {
double customerNumbers; // used to increment from 100000 - 99999. An easy way to give out new numbers and to prevent duplicates.
map <double, Customer*> cDatabase;
map <double, Customer*>:: iterator it;
public:
CustomerDatabase() {
customerNumbers = 100000;
loadCustomers();
}
void printMap() { //How do i verify what's in my map??!!!!!!!!!!!!!!!!!!!!!!!!
for (it = cDatabase.begin(); it != cDatabase.end(); it++)
{
double temp = 0;
temp = it->first;
cout << "Key: " << it->first << endl;
cout << cDatabase[it->first]->getFirstName();
}
}
double newCustomerNumber() { // Used to generate unique customer IDs easily.
double customerNumberHolder = customerNumbers;
customerNumbers++;
return customerNumberHolder;
}
bool saveCustomer(double customerN, Customer *c) { //saves customer to database once created **NOT WORKING YET
addCustomer(customerN, c);
ofstream databaseFile; //filestream local for output
bool saveCustomer = false;
if (checkForCustomerNumber(customerN) != false) { // if the customer isn't in the database
ostringstream stream; // USED TO MAKE AN INT INTO A STRING. Local stream to keep clear
stream << c->getCustomerNumber();
databaseFile.open ("database/databaseFile.csv", ios::app);
string customerHolder = c->getFirstName() + "," + c->getLastName() + "," + c->getPhoneNumber() + "," + c->getEmailAddress() + "," + stream.str() + "\n" ;
databaseFile << customerHolder;
databaseFile.close();
saveCustomer = true;
}
cout << "Customer saved Status: " << saveCustomer << endl;
return saveCustomer;
}
bool addCustomer(double customerN, Customer *c) {
bool addCustomer = false;
cDatabase[customerN] = c;
return addCustomer;
}
private:
bool loadCustomers() {
string firstN, lastN, phoneN, emailA;
double customerN;
const int FIRSTNAME = 0;
const int LASTNAME = 1;
const int PHONENUMBER = 2;
const int EMAIL = 3;
const int CUSTOMERNUMBER = 4;
//skipped 5 because every new line also runs through the while loop.
const int ADDTODATABASE = 5;
ifstream databaseFile; //file-stream local for input
databaseFile.open ("database/databaseFile.csv", ios::in);
string line = "";
int i = 0;
double loadedCustomers = 0; //used to keep track of customer loaded.
while( getline(databaseFile, line, ',')) {
if (i == FIRSTNAME) {
firstN = line;
i++;
} else if (i == LASTNAME) {
lastN = line;
i++;
} else if (i == PHONENUMBER) {
phoneN = line;
i++;
} else if (i == EMAIL) {
emailA = line;
i++;
} else if (i == CUSTOMERNUMBER) {
double customerNumb = atoi(line.c_str());
customerN = customerNumb;
Customer c(firstN, lastN, phoneN, emailA, customerN);
Customer *holder;
holder = &c;
addCustomer(c.getCustomerNumber(), holder);
i = 0; //resetting for next line.
}
//this is how i was saving a customer to the database. I dont' need to save when loading customers. saving code incase needed// saveCustomer(c.getCustomerNumber(), c);
}
databaseFile.close();
}
bool checkForCustomerNumber(double customerN) { //If ID # is within the database, it will return a true that the ID exists
bool customerNumberMatch = false;
if((cDatabase.find(customerN)) != (cDatabase.end())) { //if the customer number is the key for the map, it will not reach the end. therein the customer is already in the database
customerNumberMatch = true;
customerNumbers++;
}
cout << "C. Number Match Satus: " << customerNumberMatch << endl;
return customerNumberMatch;
}
};
///////////////////////////////////////////////////////////////////////////////
//MAIN////////////////MAIN/////////////MAIN////////////////MAIN/////////MAIN///
///////////////////////////////////////////////////////////////////////////////
int main() {
//CUSTOMER DATABASE CREATION
CustomerDatabase customerDatabase; //creating database
////CUSTOMER
Customer JT("Johnny", "Tester", "989-123-4567", "johnnyTester@gmail.com", customerDatabase.newCustomerNumber()); // used to create a test customer
Customer Test ("This", "is", "a", "test", 100000);
Customer TT("Timmy", "Tester", "989-989-9898", "Erik@itsaTest.com", customerDatabase.newCustomerNumber());
//CUSTOMER DATABASE USED
Customer *holder;
holder = &JT;
customerDatabase.saveCustomer(holder->getCustomerNumber(), holder);
holder = &TT;
customerDatabase.saveCustomer(holder->getCustomerNumber(), holder);
holder = &Test;
customerDatabase.saveCustomer(holder->getCustomerNumber(), holder);
customerDatabase.printMap();
//EMPLOYEE
Employee EP ("Erik", "Plachta", "123456", "EPlachta"); //creating test employee
// printEmployee(EP); //making sure employee can login / was created correctly.
cin.get();
return 0;
}
//Customer class looks at database for an ID it wants to use,
答案 0 :(得分：0)
在开始选择容器之前，我想谈谈ID号的数据类型选择。您使用的是double，它是一个浮点数，但您只需要整数值，因此使用整数类型会更加明智。
容器的选择取决于您计划如何访问和修改容器中的数据。需要考虑的一些关键特征是：
您是否需要能够以随机顺序访问容器中的元素？ IE浏览器。通过ID查找元素？对此有利的容器是map，unordered_map，vector。列表对此不利，因为您必须遍历列表才能找到所需的元素。
您是否需要能够以某种预定顺序（例如密钥顺序）迭代值？对此有利的容器是地图，矢量，各种列表类型。
您是否需要能够在任何给定位置插入元素？或者仅在最后插入是否足够？如果前者那么map，unordered_map，list都不错。如果是后者那么矢量就好了。
将使用哪种类型的密钥来查找值？您可以按整数查找向量中的条目，但如果您有一个字符串，则需要使用map或unordered_map。
如果键是数字 - 列表稀疏吗？ IE浏览器。序列中会有很大的空白吗？如果是，则向量不太有吸引力，因为可能存在大量浪费的内存。
您的特征似乎是：
如果不是最后一点，矢量实际上可能是比地图更好的选择。向量很便宜，并且对于您将使用的大多数操作都具有高性能。
无论如何，如果您确定地图是最好的，根据您对应用程序的了解，那么当您遍历地图时，迭代器指向容器的value_type，在地图的情况下，输入std :: pair，其中K是键类型，V是值类型。此值类型存储您使用＆＃39; first＆＃39;访问的密钥和值。和第二个＆＃39;成员。
for (it = cDatabase.begin(); it != cDatabase.end(); it++) {
cout << "Key: " << it->first << endl;
cout << it->second->getFirstName() << endl;
}