Why is my destructor being called and how can I fix it

Question

I have issues with my destructor in my c++ program.When I run the program and take the users input, it suddenly calls the destructor before the cout can even print inside the statement. Assume that the user input will be one because I designed this part of the code to only take in the input 1. I thought the destructor gets called when you leave the scope so I was thinking that the destructor should be called atleast after the cout in the if statement which I will comment below to make it easier for you guys to read. If someone can explain my mistake and correct it that would be great! In my headerfile I have

#include <iostream>
#include <string>
#include <stdlib.h>
#include <time.h>

using namespace std;

class creature{
public:
    creature();//default constructor
    creature(int a);
    ~creature();//desconstructor 
    string getName();//accessor for the name
    static int getNumObjects();
private:
    string name;
    int happy_level;
    static int count;
};

In my implementation file I have

#include "creature.h"

int creature::count=0;//initialize static member variable

creature::creature(){//default constructor
    name="bob";
    ++numberobject;
    
    cout<<"The default constructor is being called"<<endl;
}

creature::creature(int a)
{
    if(a==1)
    {
        name="billybob";
       
    }
    
    
    else if(a==2)
    {
        name="bobbilly";
       
    }
    
    else if(a==3)
    {
        name="bobbertyo";
        happy_level=1;
    }
}

creature::~creature()
{
    cout<<"The destructor is now being called"<<endl;
    cout<<creature::getName()<<" is destroyed."<<endl;
     --count;
    cout<<"Now you have a total number of "<<creature::getNumObjects()<<" creature"<<endl;
}

and in my main class I have

#include "creature.h"

int main()
{

   creature foo;//this is where the default constructor gets called which is good
   int choice;
   
   cout<<"enter 1 2 or 3 to choose ur monster"<<endl;
   cin>>choice;

   foo=creature(choice);

   if(choice==1)
    {
        cout<<"hi"<<endl;//the destructor gets called before hi is printed out and I don't know why thats happening
    }

}

Answer 1

When you do this

foo=creature(choice);

a temporary creature object is created on the RHS of the assignment. Its destructor is called once the statement is done, i.e. at end of the line.

There isn't really anything to fix, but you can initialize foo after reading in choice, rather than default initializing and then assigning:

int choice;

cout<<"enter 1 2 or 3 to choose ur monster"<<endl;
cin>>choice;

creature foo(choice);

Answer 2

As juanchopanza pointed out in his answer, the line

foo = creature(choice);

creates a temporary creature object before assigning it to foo. If you don't want this to happen, create it with

creature foo(choice);

Answer 3

To add to the other answers, your question referred to "fixing the destructor". There is nothing to fix, however there may be a bug in what you're trying to accomplish due to the destructor being invoked.

What will happen with your current code is that temporary copies may be created without you tracking them. When their destructor is called, you will decrement the count variable inadvertently, possibly giving you a negative value for count.

If you want the object static count member variable to correctly reflect the number of objects created and destroyed, your class is missing a user defined copy constructor to track the number of instances.

You need to add this function.

class creature{
public:
    creature(const creature& c) : 
         name(c.name), happy_level(c.happy_level) { ++count; }
};

This function will be called when you make copies or assign.

Live Examples:

(original code): http://coliru.stacked-crooked.com/a/ea9821e622aa4cdc

(changed code): http://coliru.stacked-crooked.com/a/b774a896377bdf97

The only difference is that the original code has the copy constructor commented out, while the changed code has the copy constructor intact.

Note that in the original code, I wanted to know how many objects are created and destroyed, but I got back a result of -1 when the final object was destroyed. This is not correct as obviously the result should yield 0, meaning all creatures are destroyed.

The changed code shows the correct number, and that is because the object creation of the temporary creature was taken into account.