C++ Programming - Constructors and Destructors - Discussion

Using singleton the constructor could be private.

e.g:
class TestSingleton{

private:
static TestSingleton * mInstance;
int mValue;
TestSingleton() {
mValue = 0;
}
public:

static TestSingleton *get_instance(){
if (TestSingleton::mInstance == nullptr){
TestSingleton::mInstance = new TestSingleton();
}
return TestSingleton::mInstance;
}

void set(int value){
this->mValue = value;
}

int get(){
return this->mValue;
}
};
TestSingleton *TestSingleton::mInstance = nullptr;


int main()
{
TestSingleton * sin = TestSingleton::get_instance();
TestSingleton * sin2 = TestSingleton::get_instance();
sin->set(10);
printf("value = %d\n", sin->get());
printf("value = %d\n", sin2->get());
}

Answer C is wrong (It is necessary that a constructor in a class should always be public.)

B is wrong because if we have defined one or more argument constructor then the compiler will never provide zero argument constructor we have to provide it explicitly.

#include <iostream>
#include <string>
using namespace std;

class name
{ public:
name(string s)
{cout<<s<<endl;
}
};

int main()
{ name s1("abc");
name s2; // complier will show an error -> we must add constructor name(){ ...} too.
return 0;
}

Constructor is a member function!

@Amit Kumar Giri.

Your Explanation is very accurate. Thanks.