For example,
class A {}; // This is blank
class B {int i}; // This is not.
How to know if a class or a class's object is blank or not?
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user1899020
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1What is your definition of blank ? what about inner class, typedef, friend declaration ? – Jarod42 Jun 20 '14 at 14:33
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How would you tell if an integer is blank? The value of zero may be valid? – Thomas Matthews Jun 20 '14 at 16:57
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You need what is called "reflection". reflection is the ability to inspect a type for its methods, member etc. The "usual" kind of reflection is not possible in C++, however there are ways to do it.
I suggest you read this answer here:
How can I add reflection to a C++ application?
or this one:
Is there an easy way to tell if a class/struct has no data members?
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Yonatan Nir
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I don't think reflection is the right word. It is called meta-programming. Reflection is more about query type information at runtime. – Bryan Chen Jun 20 '14 at 14:41
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@BryanChen http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3814.html -- the feature of being able to examine the contents of C++ types at compile time is being called "compile time reflection". This is appropriate, because as a feature it lets you also implement run-time reflection (by using compile-time reflection, then metaprogram a run-time reflection system). – Yakk - Adam Nevraumont Jun 20 '14 at 14:45