How to declare a Vector object in c++? - c++

Question

im new to learning c++ and iam now in the stage of creating a class that contains a vector of a class object, with methods to add new objects and print them all out.
Here is my code so far:
BankAccount.h:
#ifndef BANKACCOUNT_H
#define BANKACCOUNT_H
#include <string>
using namespace std;
class BankAccount
{
public:
BankAccount(string C_Name,int C_Balance);
/*
void SetCustomerName(string C_Name);
String GetCustomerName();
void SetCustomerBalance(int C_Balance);
int GetCustomerBalance();
*/
int deposit(int deposit_);
int withdraw(int withdraw_);
private:
string customer_name;
int customer_balance = 0;
int Deposit = 0;
int Withdraw = 0;
};
#endif // BANKACCOUNT_H
BankAccount.cpp:
BankAccount::BankAccount(string C_Name,int C_Balance)
{
customer_name = C_Name;
customer_balance = C_Balance;
}
int BankAccount :: deposit(int deposit_){
Deposit = deposit_;
Deposit = Deposit + customer_balance;
cout << "\nDeposit Balance = " << Deposit;
customer_balance = Deposit;
return customer_balance;
}
int BankAccount :: withdraw(int withdraw_){
Withdraw = withdraw_;
Withdraw = customer_balance - Withdraw;
customer_balance = Withdraw;
cout<<"After Withdraw Balance is "<<customer_balance;
return customer_balance;
}
Bank.h
#ifndef BANK_H
#define BANK_H
#include <vector>
#include "BankAccount.h"
using namespace std;
class Bank
{
public:
//variables , lists
vector<BankAccount> newAccount;
BankAccount bk;
// constructor
Bank();
};
#endif // BANK_H
Bank.cpp:
#include "Bank.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
Bank :: Bank()
{
string Customer_name = " ";
int Customer_balance = 0;
cout << "Add name please ";
cin >> Customer_name ;
cout << "How much balance?";
cin >> Customer_balance;
newAccount.push_back(bk(Customer_name,Customer_balance));
}
The BankAccount class is fine, the main problem is in the Bank class.
I have created the bank class to create a vectors of BankAccount , with methods that adds all the BankAccount and print them all out.
However this error keeps appearing under the constructor of Bank.cpp:
error: no matching function for call to 'BankAccount::BankAccount()'
It seems that whenever im trying to declare the class object inside the BankAccount vector , the error keeps on occuring.Can someone please explain what am i doing wrong and how to fix this?

Answer 1

The problem is not having a std::vector of BankAccounts. The problem is that your Bank class has a data member defined: BankAccount bk; Since you don't have any explicit constructor arguments, it tries to use the default constructor BankAccount(). There is no constructor declared, so you get a compilation error.
I suspect that you don't actually need that bk data member and should probably just remove it.
The next issue is when you try to push_back you are calling the bk object instead of constructing an object. What you want is to just have
newAccount.push_back(BankAccount(Customer_name,Customer_balance));
If you're using C++11 or greater (which it looks like you are) you can use emplace_back instead
newAccount.emplace_back(Customer_name,Customer_balance);
This would leave your Bank Account class as follows:
class Bank {
public:
std::vector<BankAccount> newAccount;
Bank();
};
Bank::Bank() {
std::string Customer_name = " ";
int Customer_balance = 0;
std::cout << "Add name please ";
std::cin >> Customer_name ;
std::cout << "How much balance?";
std::cin >> Customer_balance;
newAccount.emplace_back(Customer_name,Customer_balance);
}

Answer 2

You simply forgot to implement the constructor of your BankAccount class.
BankAccount::BankAccount(string C_Name,int C_Balance)
: customer_name(C_name)
, customer_balance(C_Balance)
{
// TODO;
}
As a side note, you probably want you input parameter C_name to be a const std::string& cName (using camelCase to be coherent, so a variable should never start with a capital letter, it's only used for Classes and Structs).
Usually, we use variable_ for private members (you did the opposite).
Another tip, variables should be initialized out of the body of the constructor.
EDIT:
// This is wrong
newAccount.push_back(bk(Customer_name,Customer_balance));
It should be:
// Construct a valid BankAccount object using it's constructor to fill the vector
newAccount.push_back(BankAccount(Customer_name, Customer_balance));
The variable bk is useless and needs a default constructor BankAccount::BankAccount() hence the error.

Answer 3

You have not defined a default constructor. When you use push_back it will try to default construct the object then copy the one you are passing in. You also default construct the member bk in Bank. You have 2 options to fix this problem.
Define a default constructor, ie. BankAccount() {
If you are in c++11 you can use vectors emplace_back routine. You will need to redesign to remove the bk member from Bank.

Answer 4

All objects contained by a class are constructed before the body of the constructor. In this case, your Bank object directly contains a BankAccount object, bk, which is constructed before the opening { in your Bank constructor:
Bank :: Bank()
// ... bk is initialized here....
{
You attempt to give bk some arguments later, in the call to newAccount.push_back, but it's too late; the bk object has been initialized.
To control how objects are initialized in a constructor, you must put calls to their constructors in the initialization list:
Bank :: Bank()
: bk(Customer_name,Customer_balance)
{
... but of course you haven't yet defined Customer_name or Customer_balance.
So let's back up a bit: why are you pushing an account into your Bank when you initialize the Bank? Why would an account even exist at this point? Why does Bank have bk as a member? (Why is that one account treated specially, when there's a whole vector of accounts that are also contained by the Bank?) And how are you going to add more accounts later?
So, try this: first, default-initialize the Bank:
Bank :: Bank() {}
...or, in the header (if you're using C++11 or C++14, which you should be):
Bank(void) =default;
Then, add a method for adding accounts:
Bank::addAcount(void)
{
// ... use stdin/stdout to get `customer_name` and `customer_balance`...
newAccount.emplace_back(customer_name,customer_balance);
}
(Note that you'll need to add push_back instead of emplace_back if you're not using C++11 or C++14.)

Answer 5

It seems that there is no standard constructor BankAccount::BankAccount() defined in your BankAccount.h.
But when you declare the standard constructor then you run in the following error
Error 1 error LNK2019: unresolved external symbol "public: __thiscall BankAccount::BankAccount(void)" (??0BankAccount##QAE#XZ) referenced in function "public: __thiscall Bank::Bank(void)" (??0Bank##QAE#XZ) [...]
Means that the member variable Bank::bk is declared but never defined.
So to compile your code successfuly I recommend to remove the declaration of the member variable bk in the class Bank. It makes no sense. Then do the following in your Bank class.
Bank::Bank()
{
string Customer_name = " ";
int Customer_balance = 0;
cout << "Add name please ";
cin >> Customer_name;
cout << "How much balance?";
cin >> Customer_balance;
BankAccount bankAccount(Customer_name, Customer_balance);
newAccount.push_back(bankAccount);
}
You will verify successfuly that the vector newAccount get filled with a new BankAccount object.