I am quite new to C++ and have observed, that the following lines of code act differently
MyClass c1;
c1.do_work() //works
MyClass c2();
c2.do_work() //compiler error c2228: left side is not a class, structure, or union.
MyClass c3{};
c3.do_work() //works
with a header file as
class MyClass {
public:
MyClass();
void do_work();
};
Can you explain me, what the difference between the three ways of creating the object is? And why does the second way produce a compiler error?
The second version
MyClass c2();
is a function declaration - see the most vexing parse and gotw .
The first case is default initialisation.
The last case, new to C++11, will call the default constructor, if there is one, since even though it looks like an initialiser list {}
, it's empty.
Ways one and three call the default constructor.
MyClass c3{};
Is a new initialization syntax called uniform initialization . This is called default brace initialization. However:
MyClass c2();
Declares a function c2
which takes no parameters with the return type of MyClass
.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.