CODEWITHSUNDEEP
c++classfunctionvariables
Garrettchap1
Garrettchap1

Reputation: 79

C++ Class isn't returning the correct value of my private variable

Im trying to get this program to take the users input and put that into a public function and assign it to the privateVariable, then I want it to return the value of privateVariable to main() and output it to the screen, but all it displays is the value of an undefined int ( -858993460 ). What logical problem am I having here ?

#include <iostream>
#include <string>

using namespace std;

class MyClass
{

    private:
        int privateVariable;

    public:
        int userVariable;

    void setVariable(int userVariable)
    {  
        privateVariable = userVariable;             
    } 

    int getVariable()
    {
        return privateVariable;                     
    } 

};

int main()
{
    int userVariable;
    cin >> userVariable;

    MyClass object1;
    MyClass object2;

    object1.setVariable(userVariable);        
    object2.getVariable();                   

    cout << object2.getVariable();            

    system("PAUSE");

    return 0;
}

Upvotes: 2

Views: 1646

Answers (3)

Luchian Grigore
Luchian Grigore

Reputation: 258618

You are not setting the variable. You call setVariable on object1 and getVariable on object2, so the member of object1 remains uninitialized.

object1.setVariable(5); // object1.privateVariable = 5
                        // object2.privateVariable -> still uninitialized
object2.getVariable();  // returns uninitialized variable

For this to work, depending on what you want:

class MyClass
{
private:
   static int privateVariable;
//......
}

This way, privateVariable will be a class-scoped member, not instance-scoped. That means it has the same value for all instances of the class (and even if instances were not created). This also means you can make both your functions static:

class MyClass
{
private:
   static int privateVariable;
public:
   static void setVariable(int userVariable)
   {  
      privateVariable = userVariable;             
   } 

   static int getVariable()
   {
      return privateVariable;                     
   } 
};

and you can call the methods without instances:

MyClass::setVariable(5); //MyClass.privateVariable = 5;
MyClass::getVariable(); //returns 5
object1.getVariable(); //returns also 5

Another option is, if you don't want static members, to set the member for both objects:

object1.setVariable(5); // object1.privateVariable = 5
                            // object2.privateVariable -> still uninitialized
object2.setVariable(5); //object2.privateVariable = 5
object2.getVariable();  // returns 5

Or, you could define a constructor and set the variable there:

class MyClass
{
private:
   static int privateVariable;
//......
public:
   MyClass()
   {
      privateVariable = 5;
   }
}

With this, every object you create will have the member initialized to 5.

Upvotes: 1

taskinoor
taskinoor

Reputation: 46037

You are setting in object1 and getting from object2. object1 and object2 are different objects. As variable in object2 is not set, you get a garbage value.

And I see no use of public userVariable in MyClass.

Upvotes: 6

Jonas B
Jonas B

Reputation: 2391

object2 does not have your variable initialized as you set it on object1, the code you posted would only work if privateVariable was static.

Upvotes: 0

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