CODEWITHSUNDEEP
c++oopconstructor
Santosh Sahu
Santosh Sahu

Reputation: 2244

No error for not initializing reference variable of class

I am a newbie and have a basic doubt about relationship between object creation and constructors.

Program- 1

 #include<iostream>
 using namespace std;
 class xxx{
     private: int x;
     public: xxx(){cout<<"constructer is called"<<endl;}
 };
 int main(int argc, char *argv[])
 {
     xxx x1;        //Constructor is called
     return 0;
 }

Output- constructor is called

Program- 2

 #include<iostream>
 using namespace std;
 class xxx{
     private: int x;
     public: xxx(){cout<<"constructer is called"<<endl;}
 };
 int main(int argc, char *argv[])
 {
     xxx x1();        //Constructor xxx() is not called.
     return 0;
 }

Output- blank Any information is very helpfule

Upvotes: 1

Views: 76

Answers (2)

taocp
taocp

Reputation: 23634

 xxx x1;

creates an object of class xxx, therefore, calls default constructor of class xxx.

xxx x1();

declares a function that returns an object of class xxx and function name is x1, takes no parameter. It is not an instantiation of class xxx, therefore, there is no constructor being called.

Upvotes: 2

hmjd
hmjd

Reputation: 121971

This:

xxx x1();

is a function declaration (function called x1 taking no arguments and returning an xxx), not a variable declaration so no instance of xxx is created (hence no constructor call).

Upvotes: 4

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