CODEWITHSUNDEEP
c++pointersreference
Au Ris
Au Ris

Reputation: 4659

calling a method wont change the value unless from within the method itself

I am trying to figure out my mistake.

I am working on Account class in C++, where there are a few methods like credit(), debit(), etc.
I wrote a transfer() method and the problem I get is that it takes "money" out of account a1 but does not credit the a2. However if I print it within the method itself in account.cpp it does show the correct result, while in main the balance stays the same.

Can you see my mistake? Something to do with reference, pointers, etc?
Here is the main:

a1.println(); 
a2.println();
cout<< "Valid parameter " << endl;
cout<< a1.transfer(a2, 13) << endl;
a1.println();
a2.println();

Here is what it prints:

(Account(65,140))
(Account(130,100))
Valid parameter 
1
(Account(65,127))
(Account(130,100))

Here is the definition of methods:

    // withdraw money from account
    bool Account::debit(int amount){
    if (amount>=0 && balance>=amount) {
        balance=balance-amount; // new balance
        return true;
    } else {
        return false;
    }
}


// deposit money
bool Account::credit(int amount){
    if (amount>=0) {
        balance=balance+amount; // new balance
        return true;
    } else {
        return false;
    }
}

bool Account::transfer(Account other, int amount){
    if (amount>=0 && balance>=amount) {
        debit(amount);
        other.credit(amount);
        //other.println();// prints corect amount
        return true;
    } else {
        return false;
    }
}

Upvotes: 1

Views: 103

Answers (2)

alexm
alexm

Reputation: 6882

You did not pass "other" by reference 

 bool Account::transfer(Account& other, int amount){

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726599

This is because you are passing the other Account by value. The balance gets changed OK, but on a different instance of the account, meaning that the copy gets modified, while the original stays intact.

Change your code to passing Account by reference to make it work.

bool Account::transfer(Account& other, int amount)
//                            ^
//                           HERE

Upvotes: 7

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