Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
608 views
in Technique[技术] by (71.8m points)

c++ - Why can't I access a protected member from an instance of a derived class?

I haven't done C++ in a while and can't figure out why following doesn't work:

class A {
protected:
  int num;
};

class B : public A {
};

main () {
  B * bclass = new B ();
  bclass->num = 1;
}

Compiling this produces:

error C2248: 'A::num' : cannot access protected member declared in class 'A'

Shouldn't protected members be accessible by derived classes?

What am I missing?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

yes protected members are accessible by derived classes but you are accessing it in the main() function, which is outside the hierarchy. If you declare a method in the class B and access num it will be fine.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...