CODEWITHSUNDEEP
c++
megamonium
megamonium

Reputation: 483

What does this mean: "class DATA_C data_container"

I'm new to C++ and while I'm reviewing someone else's code, I ran into an expression I don't understand.

In the header file I have a normal class definition:

//in data.hpp
class DATA_C : public QThread
{
   Q_OBJECT
   // the rest of class definition...
}

A snippet of the source file:

//in data.cpp
class DATA_C data_container;

I can understand "DATA_C data", which is a declaration; but what is "class DATA_C data_container"? What does it do?

Thanks in advance.

Upvotes: 2

Views: 62

Answers (1)

M.M
M.M

Reputation: 141554

In this context tt has exactly the same meaning as DATA_C data_container;. In many contexts you can optionally use the term class X , if it would have been valid to just use X.

In general you can use class X when X has not been defined yet and it declares the class (but doesn't define it). But class DATA_C data_container; would not be allowed if DATA_C had not been previously defined, because you cannot instantiate an object of incomplete type.

Upvotes: 1

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