C++ Semantic issue: "'use of undeclared identifier 'balance'" - c++

Question

I am new to C++ and using Xcode and I am having an issue,
in my main .cpp file Account.cpp the code is-
#include <iostream>
using namespace std;
#include "Account.h"
Account::Account()
{
double balance=0;
balance=0;
}
Account getbalance()
{
return balance;
}
void deposit(double amount)
{
balance+=amount;
}
void withdraw(double amount)
{
balance-=amount;
}
void addInterest(double interestRate)
{
balance=balance*(1+interestRate);
}
I think I missed something but I'm not sure where, any help would be appreciated thank you.
**The header file Account.h is-
#include <iostream>
using namespace std;
class Account
{
private:
double balance;
public:
Account();
Account(double);
double getBalance();
void deposit(double amount);
void withdraw(double amount);
void addInterest(double interestRate);
};

Answer 1

Write the constructor the following way
Account::Account()
{
balance = 0.0;
}
I suppose that balance is a data member of type double of class Account.
Or you can write
Account::Account() : balance( 0.0 ) {}
And all these function definitions if the functions are class member functions must look at least like
double Account::getBalance()
{
return balance;
}
void Account::deposit(double amount)
{
balance+=amount;
}
void Account::withdraw(double amount)
{
balance-=amount;
}
void Account::addInterest(double interestRate)
{
balance=balance*(1+interestRate);
}
Also it seems that you forgot to define the constructor with a parameter.
Account::Account( double initial_balance ) : balance( initial_balance ) {}