call one constructor from another constructors in one class

Question

I've encountered the following question online.

If we call one constructor from another in a class, what will happen?

Can anyone give me some hints?

Well, in C++, there are copy constructors that use some other constructors, to clone an object's data from other object. So that basically does what you're questioning here. You can look into that. — bad_keypoints, Jul 01 '15 at 05:09
Assuming C++11: You can read about delegating Constructors [here](http://en.cppreference.com/w/cpp/language/initializer_list#Delegating_constructor). — namezero, Jul 01 '15 at 05:09

score 4 · Answer 1 · edited May 23 '17 at 11:58

4

in java also its possible with the power of the this keyword. check out the example given below.

public class A {

    public A() {
        //this("a");
        System.out.println("inside default Constructor");
    }

    public A(String a){
        this();
        System.out.println("inside Constructor A");
    }

}

This concept is called constructor chaining. If it's c# i found this saying it's possible Is nesting constructors (or factory methods) good, or should each do all init work

edited May 23 '17 at 11:58

Community

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answered Jul 01 '15 at 05:20

Mightian

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no @leppie it says **assume**, thats y i just gave my 0.02$ on the various oop language – Mightian Jul 01 '15 at 05:33
that was me. The question is too broad to cover all languages. – leppie Jul 01 '15 at 05:34

score 1 · Answer 2 · edited May 23 '17 at 12:21

1

This example from MSDN clarifies it

To add delegating constructors, constructor (. . .) : constructor (. . .) syntax is used.

class class_a {
public:
    class_a() {}
    // member initialization here, no delegate
    class_a(string str) : m_string{ str } {}

    // can’t do member initialization here
    // error C3511: a call to a delegating constructor shall be the only member-initializer
    class_a(string str, double dbl) : class_a(str) , m_double{ dbl } {}

    // only member assignment
    class_a(string str, double dbl) : class_a(str) { m_double = dbl; }
    double m_double{ 1.0 };
    string m_string;
};

Read answers from Can I call a constructor from another constructor (do constructor chaining) in C++? too.

edited May 23 '17 at 12:21

Community

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answered Jul 01 '15 at 05:37

Shreevardhan

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Just another reason why I steer clear of C++. Syntax is way too complex. – leppie Jul 01 '15 at 05:44
@leppie Yes, it is, if you compare with counterparts like Java – Shreevardhan Jul 01 '15 at 05:45
i have to agree with @leppie syntax in java is pretty decent – Mightian Jul 01 '15 at 06:17

call one constructor from another constructors in one class

2 Answers2