如果我将构造函数声明为私有，可以在另一个类中调用此构造函数 [英] if I declare a constructor as private can i call this constructor in another class

问题描述

如果我将构造函数声明为私有，可以在另一个类中调用该构造函数吗?

If I declare a constructor as private can I call this constructor in another class?

class A{

private A(){

...
}


class B {

A  a_obj=new A(){}           //shows an error--not visible 

}

无论如何，我都想声明一个私有构造函数，但是我不能违反它，但是我仍然可以以其他方式使用它吗?

I want to declare a private constructor anyhow, I can''t violate that, but still can I use it in other way around?

推荐答案

使用私有构造函数.

请参阅此 [

You cannot initialize a object using private constructor.

Please see this[^]

不仅您不能实例化具有所有私有构造函数的类(不是从类的外部，而是类可以提供一个创建实例的工厂)，但这也是一种众所周知的编程方法.

特别是，这是创建抽象类功能的唯一方法(与较新的OOP语言相比，C ++中没有抽象"关键字).这样的类非常有用，因为一个类层次结构需要一个具有通用功能的通用基类，而该通用基类只能用作基类.用编译器阻止的意外尝试创建此类的实例.

—SA

Not only you cannot instantiate a class with all constructors private (not from outside of the class, but class can provide a factory creating an instance), but this is also a well known method of programming.

In particular, this is the only way to created functionality of abstract classes (there is no "abstract" keyword in C++, in contrast to newer OOP languages). Such classes are very useful it a class hierarchy needs a common base class with common functionality which can only be used as a base class; an accidental attempt to create an instance of such class with be prevented by compiler.

—SA

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