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Jan 17th, 2009

Inheritance errors

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I have made a base class and a derived class and I am having a couple compile errors.

Quote ...

SavingsAccount.hpp(9) : error C2512: 'Account' : no appropiate default constructor available

What i want to do is be able to give the savings account an inital balance and it changes the currentBalance variable in the account class.

Base class

C++ Syntax (Toggle Plain Text)
#include <iostream>
using namespace std;
 
class Account {
 
	friend class SavingsAccount;
	//friend class CheckingAccount;
 
	double deposit;
	//double withdrawal;
 
	public:
		Account(double newBalance) {//, double deposit, double withdrawal) {
			currentBalance = newBalance;
			//newBalance >= 0 ? currentBalance += newBalance : cout << "Initial balance invalid";
		};
 
		~Account() { };
 
		int getBalance() { return currentBalance; }	
 
		void credit() { currentBalance += deposit; }
 
		//void debit() { currentBalance >= withdrawal ? currentBalance -= withdrawal : cout << "Debit amount exceeded account balance"; }
 
	private:
		double currentBalance;
 
};
#include <iostream>
using namespace std;

class Account {

	friend class SavingsAccount;
	//friend class CheckingAccount;
	
	double deposit;
	//double withdrawal;

	public:
		Account(double newBalance) {//, double deposit, double withdrawal) {
			currentBalance = newBalance;
			//newBalance >= 0 ? currentBalance += newBalance : cout << "Initial balance invalid";
		};

		~Account() { };

		int getBalance() { return currentBalance; }	

		void credit() { currentBalance += deposit; }
	
		//void debit() { currentBalance >= withdrawal ? currentBalance -= withdrawal : cout << "Debit amount exceeded account balance"; }
	
	private:
		double currentBalance;

};

derived class

C++ Syntax (Toggle Plain Text)
#include "Account.hpp"
#include <string>
 
class SavingsAccount : public Account {
 
	double Balance;
 
	public:
		SavingsAccount(double initBalance, double initInterestRate) {
			InterestRate = initInterestRate;
			Balance = initBalance;	
		};
 
		~SavingsAccount() { };
 
		void CalculateInterest(Account& ac, double InterestRate) {
			ac.getBalance *= InterestRate;
		};
 
	private:
		double InterestRate;
 
};
#include "Account.hpp"
#include <string>

class SavingsAccount : public Account {

	double Balance;
	
	public:
		SavingsAccount(double initBalance, double initInterestRate) {
			InterestRate = initInterestRate;
			Balance = initBalance;	
		};

		~SavingsAccount() { };

		void CalculateInterest(Account& ac, double InterestRate) {
			ac.getBalance *= InterestRate;
		};

	private:
		double InterestRate;

};

main program
#include "SavingsAccount.hpp"

C++ Syntax (Toggle Plain Text)
int main() {
 
	Account account(75.00);
	SavingsAccount savings(100.00, 2.5);
 
	cout << "Current Balance:" << account.getBalance();
 
	return 0;
}
int main() {
	
	Account account(75.00);
	SavingsAccount savings(100.00, 2.5);
	
	cout << "Current Balance:" << account.getBalance();

	return 0;
}

Last edited by AdRock; Jan 17th, 2009 at 9:14 am.

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AdRock

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Jan 17th, 2009

Re: Inheritance errors

>>SavingsAccount.hpp(9) : error C2512: 'Account' : no appropiate default constructor available

That means Account needs a constructor that takes no parameters.

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Jan 17th, 2009

Re: Inheritance errors

I did what you said and changed the constructor so it takes no values but i still get errors

Quote ...

TestAccount.cpp
TestAccount.cpp(5) : error C2664: 'Account::Account(const Account &)' : cannot convert parameter 1 from 'double' to 'const Account &'
Reason: cannot convert from 'double' to 'const Account'
No constructor could take the source type, or constructooverload resolution was ambiguous

Also i need the constructor to take an initial value

AdRock

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Jan 17th, 2009

Re: Inheritance errors

well when you create the object of the child class the base class ctor gets called and since you have declared your own ctor the compiler doesn't give you a default ctor. In the definition of the child class ctor you should pass the required value to the base class ctor.

something like

c++ Syntax (Toggle Plain Text)
SavingsAccount(double initBalance, double initInterestRate):Account(initBalance) {
			InterestRate = initInterestRate;
			Balance = initBalance;	
		};
SavingsAccount(double initBalance, double initInterestRate):Account(initBalance) {
			InterestRate = initInterestRate;
			Balance = initBalance;	
		};

Agni

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Jan 17th, 2009

Re: Inheritance errors

Click to Expand / Collapse Quote originally posted by AdRock ...

I did what you said and changed the constructor so it takes no values but i still get errors

Also i need the constructor to take an initial value

you can have as many constructors as you like.

Ancient Dragon

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Jan 17th, 2009

Re: Inheritance errors

I was going to give you Agni's answer (lucky I saw it when I switched to Advanced).

Also, there is no requirement that a class have only one constructor.

You could actually declare both (not that you want to in this instance):

c++ Syntax (Toggle Plain Text)
Account(double newBalance) {
	currentBalance = newBalance;
};
Account() {
	currentBalance = 0;
};
Account(double newBalance) {
	currentBalance = newBalance;
};
Account() {
	currentBalance = 0;
};

(Arg! I must type slow, Dragon said this already)

Design Comment:

I'm not overly fond of adding friends to a class (I do it when I need to, but try to avoid it when possible). You should not need to make derived classes a friend of the parent. If you have things that you want derived classes to be able to see / modify, make them protected instead of private, or provide protected accessors if that works better for you.

Last edited by Murtan; Jan 17th, 2009 at 1:56 pm.

Murtan

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Jan 17th, 2009

Re: Inheritance errors

Click to Expand / Collapse Quote originally posted by Agni ...

well when you create the object of the child class the base class ctor gets called and since you have declared your own ctor the compiler doesn't give you a default ctor. In the definition of the child class ctor you should pass the required value to the base class ctor.

something like
c++ Syntax (Toggle Plain Text)
SavingsAccount(double initBalance, double initInterestRate):Account(initBalance) {
			InterestRate = initInterestRate;
			Balance = initBalance;	
		};
SavingsAccount(double initBalance, double initInterestRate):Account(initBalance) { InterestRate = initInterestRate; Balance = initBalance; };

I did this but still get errors

Quote ...

TestAccount.cpp
SavingsAccount.hpp(9) : error C2664: 'Account::Account(const Account &)' : cannot convert parameter 1 from 'double' to 'const Account &'
Reason: cannot convert from 'double' to 'const Account'
No constructor could take the source type, or constructor overload resolution was ambiguous

TestAccount.cpp(5) : error C2664: 'Account::Account(const Account &)' : cannot convert parameter 1 from 'double' to 'const Account &'
Reason: cannot convert from 'double' to 'const Account'
No constructor could take the source type, or constructor overload resolution was ambiguous

AdRock

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Jan 17th, 2009

Re: Inheritance errors

where's the code for TestAccount.cpp?

Agni

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Jan 17th, 2009

Re: Inheritance errors

C++ Syntax (Toggle Plain Text)
#include "SavingsAccount.hpp"
 
int main() {
 
	Account account(75.00);
	SavingsAccount savings(100.00, 2.5);
 
	cout << "Current Balance:" << account.getBalance();
 
	return 0;
}
#include "SavingsAccount.hpp"

int main() {
	
	Account account(75.00);
	SavingsAccount savings(100.00, 2.5);
	
	cout << "Current Balance:" << account.getBalance();

	return 0;
}

AdRock

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Jan 17th, 2009

Re: Inheritance errors

To use Agni's code, Account needs the Account(double newBalance) constructor.

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