在设计Singleton模式时是否需要使赋值运算符私有

Question

I have just Learned about the first Design Pattern in my career :) and Implemented it both using early and Lazy method. While it is Logical to make the Copy Constructor Private but i was told that also make assignment operator private. Since only one instance can be created I think it does not make sense to declare Assignment operator private.

Answer 1

Since only one instance can be created I think it does not make sense to declare Assignment operator private.

It does not make sense to declare Assignment operator at all. Anyway you're right. public or private it does make any difference because it will never be used.

For those reasons the most practical choice is to avoid to define it at all, and make sure it cannot be called: C++11 has introduced that functionality.

So, you can just delete it.

Singleton& operator=(const Singleton&) = delete;

Answer 2

They may have been referring to an assignment operator which performs copying:

Singleton& operator=(const Singleton& other);

This implies multiple instances of Singleton, since you would need another instance (the 'other') to copy into the Singleton instance, which doesn't make sense. Therefore, you can make it private or mark it as deleted.