Including .h classfiles
Author
I have a problem when trying to include .h files that contain both class declarations and classbody definitions. When I do just one #include "someclass.h" everything works fine. But when I want to use the class in some other module in the project, I get compiler errors like "multiple definitions of blablabla first defined here blabla etc..." The usual:
#ifndef SOMECLASS_H
#define SOMECLASS_H
//class prototypes
//class definitions
//class body definitions
#endif
doesn´t seem to work. How can I keep both class declarations and class body definitions in a .h file and avoid getting those errors when I try to include it more than once?
the functions either need to be defined in the class:
edit:
or you could have them out of the body but only if you make them inline (as noted below).
[edited by - petewood on June 19, 2003 7:50:02 AM]
//.h#ifndef DOG_H#define DOG_H#include <string>#include <iostream>class Dog {public: Dog(const std::string name) : name_(name) { } Speak() { std::cout << "Woof Woof Woof " << name_ << std::endl; }private: std::string name_;// edit: thanks kooktroop};#endifedit:
or you could have them out of the body but only if you make them inline (as noted below).
[edited by - petewood on June 19, 2003 7:50:02 AM]
make sure you define
in the class too...
Also just as a matter of preference i use .hpp for C++ header files (those containing classes and/or namespaces etc...) you may want to as well.
std::string name_; in the class too...
Also just as a matter of preference i use .hpp for C++ header files (those containing classes and/or namespaces etc...) you may want to as well.
quote:Original post by petewood
the functions need to be defined in the class
They don''t have to be. You can have them outside of the class declaration too.
//.h#ifndef DOG_H#define DOG_H#include <string>#include <iostream>class Dog{public: inline Dog(const std::string name); inline Speak();private: std::string name_;};inline Dog::Dog(const std::string name) : name_(name){}inline Dog::Speak(){ std::cout << "Woof Woof Woof " << name_ << std::endl;}#endif
Author
quote:Original post by Poontardis
They don't have to be. You can have them outside of the class declaration too.
That´s what I´m trying to do, but I get "multiple definisions of blabla..." errors when I try to include the .h file more than once in the project. My .h files look like this:
#ifndef SOMECLASS_H#define SOMECLASS_Hclass SomeClass;class SomeClass{public://...private://...};SomeClass::SomeClass(){ }SomeClass::~SomeClass(){ }// etc...#endif // SOMECLASS_HYou´re saying this should work? Maybe it´s the compiler then? I´m using Dev-Cpp IDE and Mingw compiler.
[edited by - eckbw on June 19, 2003 7:20:48 AM]
[edited by - eckbw on June 19, 2003 7:21:19 AM]
If you allow yourself to have function bodies in the header file they shoud have a inline before the type specifier.So we will have this:
"You losers better learn...NOONE CONTROLS OUR GOD DAMN LIFE!!!" - MANOWAR
inline SomeClass::SomeClass(){}inline SomeClass::~SomeClass(){}"You losers better learn...NOONE CONTROLS OUR GOD DAMN LIFE!!!" - MANOWAR
Author
Arrgh, ok next problem. 
I have two classes in two different .h files. One of them is an abstract baseclass, and I want the other class to be a subclass of this abstract baseclass. Like this:
Now, problem is I get a "parse error before ''{'' token", like it wont recognize the ": public SomeOtherClass" part, even though I have included the other class. Am I doing something wrong here? Or is the problem in the "someotherclass.h" file? Or do I have to put the base and subclasses in the same .h file?
I have two classes in two different .h files. One of them is an abstract baseclass, and I want the other class to be a subclass of this abstract baseclass. Like this:
#ifndef SOMECLASS_H#define SOMECLASS_H#include "someotherclass.h"class SomeClass;class SomeClass : public SomeOtherClass{ // here I get a syntax errorpublic://...private://...};// class bodies#endifNow, problem is I get a "parse error before ''{'' token", like it wont recognize the ": public SomeOtherClass" part, even though I have included the other class. Am I doing something wrong here? Or is the problem in the "someotherclass.h" file? Or do I have to put the base and subclasses in the same .h file?
Author
I tried putting a
class SomeOtherClass;
in there too, but then I get "class SomeOtherClass has incomplete type" error. I want to keep the classes in separate .h files but still be able to inherit from a baseclass, is that possible? Or do I have to put them all in a single .h file?
class SomeOtherClass;
in there too, but then I get "class SomeOtherClass has incomplete type" error. I want to keep the classes in separate .h files but still be able to inherit from a baseclass, is that possible? Or do I have to put them all in a single .h file?
a) there''s no need to forward declare a class in its own header file (at least for what you''re coding just now anyway).
b) This will work fine:
which is basically what you said you had. From the compiler error it looks like your error is actually in your someotherclass.h... do you have a semi-colon at the end of the someotherclass class declaration?
b) This will work fine:
//baseclass.h#ifndef BASECLASS_H#define BASECLASS_Hclass BaseClass{public: // protected: //private: //};//inline class methods go here#endif //#ifndef BASECLASS_H////////////////////ChildClass.h#ifndef CHILDCLASS_H#define CHILDCLASS_H#include "BaseClass.h"class ChildClass : public BaseClass{public: // protected: //private: //};//inline class methods go here#endif //#ifndef CHILDCLASS_H//////////////////which is basically what you said you had. From the compiler error it looks like your error is actually in your someotherclass.h... do you have a semi-colon at the end of the someotherclass class declaration?
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