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forward reference header error Red House, West Virginia

Does an index have a currency? It's possible, but I've visually compared a few times and can't see any... –underscore_d Aug 12 at 20:11 @underscore_d, thanks for the prod. –R Sahu Aug 12 at 21:05 more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed Your second actually includes the class B.

Contents 1 Examples 2 Classes 3 Forward reference 4 References Examples[edit] A basic example in C is: void printThisInteger(int); In C and C++, the line above represents a forward declaration of Also, if you have variables of type B *, you can't dereference the pointer (because for that, too, the definition of B must be known). If you have a focus for your spell casting do you need to pay materials? c++ forward-declaration c++-faq share|improve this question edited Oct 31 '15 at 4:43 R Sahu 108k951106 asked Feb 16 '09 at 15:31 Igor Oks 13.1k1761101 4 I desperately want this to

The important distinction being some template techniques where you are explicitly NOT expected to instantiate them, mentioned just so someone doesn't get snarky with me. Instead replace with: A* a; Pointer or reference to A without A's class definition will work fine. I wasn't sure that was the case. What is the difference between a crosscut sled and a table saw boat?

Or have I missed a tiny detail that's different? Let's say you decide that it would be better to use std::list instead of std::vector. Within the header file or source file?What is the difference between declaring a header file as '#include" header.h" 'and "#include"?In C, C++(.h files) header files can we write definitions of functions XD May 3, 2009 at 8:31pm UTC Oromis (80) I thought I tested it, but it compiles fine now...

May 3, 2009 at 8:25pm UTC Disch (13766) Well basically what I'm saying is this: - If he shortcuts and puts the function bodies in the class definition, he's implicitly inlining First, each source file is compiled on its own. In a case where there is only one relation you can certainly use your second choice. Define function templates or methods using this type template void f1(X x) {} // OK if X is defined before calling f1 template X f2(){return X(); }

Add Google Website Translator to your Octopress Blog » Comments Please enable JavaScript to view the comments powered by Disqus. If that doesn't compile go for the #include. I read this in here. Your cache administrator is webmaster.

Use it by value. Here's the perfect example of why you should only #include what is necessary: 1
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// a.h -- assume it's guarded #include "b.h" class A { B* b; }; 1
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// b.h You can, however, have class A contain a pointer to class B that contains an object of class A. Then ok as example you think there are three header files vehicle.h, bus.h, toybus.h.

Hide this message.QuoraSign In C++ (programming language)What (if any) are the benefits of forward declaration over including header files?UpdateCancelAnswer Wiki1 Answer Gregory Popovitch, I've been coding in C++ for a long A well-documented template should indicate in its documentation all the requirements of its parameters, including whether they need to be complete types or not. Class B Source #include "B.h" void B::SomeFunction() { } Class B Header #include "A.h" struct A; class B { public: A a; void SomeFunction(); }; struct A Header #include "B.h" class share|improve this answer edited Oct 12 '15 at 19:06 answered May 14 '10 at 8:24 Charles Beattie 3,28711526 4 you also need to include it to use it by value.

hahahaah. So even if he tries to add the inline keyword, if he moves the functions to a .cpp file, they won't be inlined (no) I think I'll start a thread and Sum of neighbours How to prevent Beamer from repeatedly expanding macros in \frametitle when frame-breaking How to add part in eagle board that doesn't have corresponded in the schematic "jumpers"? Forward-declaration is used to avoid unnecessary coupling which help reducing compilation time by reducing the number of header inclusion.

I figured I should focus more on the instantiating method since everybody knows how to do the inlining method. You never call any function of B from the definition of A. (i.e. What does dot forward slash forward slash mean (.//)? I know that isn't a particularly technical answer but you could avoid the whole thing together by doing that if it is feasible. –ihtkwot Dec 11 '09 at 2:34

Ideally, the dependencies for the class should be layed out in the header. You: "But putting function bodies at the end of my header is ugly. This might open circular reference holes or other scenarios that might complicate the "right way" outline. 1
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class B { public: void Func(const A& a) // parameter, so forward declare is I'll edit the posts once I get it straightened out on my local copy.

May 5, 2009 at 6:28am UTC translore (31) I had a teacher "so and so" tell me not to include inside header files and I think I even read this in Can I forward declare them? –Igor Oks Feb 16 '09 at 16:15 Yes, but in that case you can only use a reference or a pointer to the forward-declared This limits what you can do with B inside a.h. right?

Don't use an #include when a forward declaration would suffice. Therefore, you cannot use the incomplete type at places where the compiler would need to know the layout of the type. does the compiler open and parse the vehicle.h again? Second, understand that in C++, the only difference between classes and structs is the default visibility level - classes use private visibility by default while structs use public visibility by default.

Not the answer you're looking for? Not the answer you're looking for? This way, if B changes, only the contents of a.cpp get recompiled, but a.h (and other files that include a.h) need not change. These intermediate files are often called object files -- but they are not to be confused with objects in your code.

A better way to evaluate a certain determinant Logical fallacy: X is bad, Y is worse, thus X is not bad Broke brake bleeder valve What sense of "hack" is involved asked 7 years ago viewed 136093 times active 2 months ago Linked 6 Use of undefined type 2 Why other class names are specified above a class? 0 How to do Like if the template class is exceedingly large and you want to ease compile time (though it would have to be pretty freaking big to make a difference) Anyway overall I okay...." 1
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#include "parent.h" #include "myclass.h" // ERROR 'std::vector' undefined 1
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#include "parent.h" #include #include "myclass.h" // ERROR 'Support' undefined so-and-so: "WTF?

int i = m->someField; // compiler error! } }; Create explicit instantiations of the class template template struct X; share|improve this answer edited Aug 12 at 21:05 answered Oct 31 '15 When it sees an include, to be able to use any information contained within, it must open the file and parse it (regardless of whether or not it actually needs to Thanks. When can I use the forward class declaration?

I'll have to read it several times to fully understand it... c++ coding-style share|improve this question asked Apr 23 '13 at 7:41 Nayana Adassuriya 199128 add a comment| 4 Answers 4 active oldest votes up vote 7 down vote accepted The compiler How to reliably reload package after change?