[CLOSED] Do constructors have to be public?

Answer 1

@Tatari it's not necessary
constructors can also be private or default if u want
as @kai an @Jay said singleton is an exemple of constructors private.

Answer 2

The public access modifier is accessible everywhere,
u can use it with : method, classes ,variable ,(constructors),packages...

Answer 3

Example of singleton (factory pattern)

https://code.sololearn.com/cnLC3sFSFO20/?ref=app

Answer 4

But do constructors HAVE TO be public?

Answer 5

No they don't. If you create a singleton for example, the constructor even has to be private.

Answer 6

Constructors don't have to be public, however there are not many cases where you'd want to have a private constructor. The singleton pattern is one of them, but I try to avoid singletons as much as possible.

An example of a private constructor I use rather often is a private copy constructor (together with a private assignment operator). Say you have class Foo, then you'd get:

private:
Foo(const Foo&) { /* do nothing */ };
Foo& operator= (const Foo&) { return *this; };

In this way people outside of your class cannot make a copy of your class. Thus if they want to pass an object of your class to a method they *must* pass a reference or pointer. This is really usefull if your class has lots of data or should be the only one in existence.

Answer 7

Move to modern c++ standards is often easier said than done, especially when your company decides to stay with c++98...

Answer 8

Constuctors can be private and also static.
However, if you have class deriving from another class, the derived class cannot invoke the constructor from the base class since it's private.