What happens when an object is assigned to a value in c++

Question

Check the following code:

#include<iostream>
using namespace std;

class example
{
    public:
    int number;

    example()
    {
        cout<<"1";
        number = 1;
    }

    example(int value)
    {
        cout<<"2";
        number = value;
    }

    int getNumber()
    {
        cout<<"3";
        return number;
    }
};

int main()
{
    example e;
    e = 10;
    cout<<e.getNumber();
    return 0;
}

What is the output of the above code. Also, I want to know what happens when an object is directly assigned to a value. How will the compiler interpret it?

*"What is the output of the above code"* - Tried running it? — StoryTeller - Unslander Monica, Sep 05 '17 at 09:56
Yes the output is: 12310 But I want to know what happens when "e = 10" is encountered. — Allen Richards, Sep 05 '17 at 09:59
Learning to use C++ is not done via asking for tutoring on SO. [Pick a good book](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) and follow that. — StoryTeller - Unslander Monica, Sep 05 '17 at 10:01
`e = 10;` causes `example(int value)` implicit constructor to be invoked constructing a temporary instance of `example` and assigning it to `e` using compiler-generated assignment operator. A good practice to avoid such behavior is marking all constructors beside default and copy/move as `explicit`. — user7860670, Sep 05 '17 at 10:01
Terminology check: you assign a value to an object, not an object to a value. — molbdnilo, Sep 05 '17 at 10:30

keyvan vafaee · Accepted Answer · 2017-09-05T10:33:28.183

first you typed

example e;

So first constructor called and 1 printed

example()
{
    cout<<"1";
    number = 1;
}

output :

then you typed : e=10 its equal to e = example(10); so another constructor called :

example(int value) /// beacause you used example(10)
{
    cout<<"2";
    number = value;
}

so your output is :

and number is 2 Finally in :

cout<<e.getNumber();


3 is couted but in the other hand value is `10`

because number = value your number is 10
So in Finally your output is :

thanx for @StoryTeller for editting explaintions

What happens when an object is assigned to a value in c++

1 Answers1