I have two clases Pet and Person
Here is the Person.h:
#ifndef PERSON_H
#define PERSON_H
#include <list>
class Pet;
class Person
{
public:
Person();
Person(const char* name);
Person(const Person& orig);
virtual ~Person();
bool adopt(Pet& newPet);
void feedPets();
private:
char* name_;
std::list<Pet> pets_;
};
#endif
And here is the Pet.h
#ifndef PET_H
#define PET_H
#include <list>
#include "Animal.h"
class Person;
class Pet : public Animal
{
public:
Pet();
Pet(const Pet& orig);
virtual ~Pet();
std::list<Pet> multiply(Pet& pet);
private:
std::string name_;
Person* owner_;
};
#endif
The problem that i have is this:
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/list.tcc:129: error: invalid use of undefined type `struct Pet'
Person.h:13: error: forward declaration of `struct Pet'
I fixed trying to put this std::list<Pet>* pets_; but when i tried to call list functions always have a link problem. My question is how a have to include a list inside a class that contains objects from another class.
The standard requires that, except where explicitly stated, you use complete types with the library templates. This basically inhibits your design (where each object maintains by value a list of the other type).
You can work around this by using [smart] pointers (either a pointer to the container or container of pointers).
Related
Pretty new to C++, I was given an assignment that is basically about utilizing two different classes, however when creating my header files and c++ files and attempting to compile I get an error that reads no matching function for call to 'Owner::Owner()'. Since I am not super familiar with C++ yet I am assuming that this issue has something to do with my constructors and the way I am trying to call them, my assignment details what I think my issue is about but I am having trouble understanding exactly what needs to be done. I will provide the assignment details on the issue, as well as the code and compilation error below. Sorry for all the information I've just been stuck with this issue for a while and I can't seem to figure out a solution.
Transcribed Error
In constructor 'Dog::Dog(std::__cxx11::string, int)':
Dog.cpp:23:46: error: no matching function for call to 'Owner::Owner()' Dog::Dog(std::string unsetBreed, int unsetAge){
Assignment Details
Now you will write a program that consists of two classes, a Dog class and an Owner class. Their specification is shown in the UML diagram below. Notice that in our design, every Dog has an Owner class member. Class Owner is immutable, as mentioned above. An immutable class is just a class whose members cannot be changed(mutated) after an object was instantiated. Therefore, the Owner class does not have any setter methods. The Owner’s class attributes must be set at the time of creation(in the Owner’s constructor). You will call Owner’s constructor from inside Dog’s constructor. Do not forget to do it inside each constructor in class Dog.
Dog.h File
#ifndef DOG_H_INCLUDED
#define DOG_H_INCLUDED
#include <iostream>
#include "Owner.h"
class Dog {
//-----------------------//
private:
std::string breed;
int age;
Owner owner;
static int dogCount;
//-----------------------//
public:
Dog();
Dog(std::string, int);
std::string getBreed();
int getAge();
void setBreed(std::string);
void setAge(int);
void printDogInfo();
int getDogCount();
};
#endif // DOG_H_INCLUDED
Owner.h File
#ifndef OWNER_H_INCLUDED
#define OWNER_H_INCLUDED
#include <iostream>
class Owner {
//-----------------------//
private:
std::string name;
int age;
//-----------------------//
public:
Owner(std::string, int);
std::string getName();
int getAge();
//-----------------------//
};
#endif // OWNER_H_INCLUDED
Dog.cpp File
#include <iostream>
#include "Owner.cpp"
#include "Owner.h"
#include "Dog.h"
//---------------SETTERS------------------//
void Dog::setBreed(std::string dogBreed){dogBreed = breed;}
void Dog::setAge(int dogAge){dogAge = age;}
//--------------GETTERS------------------//
std::string Dog::getBreed(){return breed;}
int Dog::getAge(){return age;}
int Dog::getDogCount(){return dogCount;}
//--------------OTHERS-------------------//
Dog::Dog(std::string unsetBreed, int unsetAge){
Owner::Owner(std::string unsetName, int unsetOwnerAge);
Dog::setBreed(unsetBreed);
Dog::setAge(unsetAge);
}
void Dog::printDogInfo(){
Dog::getBreed();
Dog::getAge();
}
Owner.cpp File
#include <iostream>
#include "Owner.h"
#include "Dog.h"
//--------------GETTERS------------------//
int Owner::getAge(){return age;}
std::string Owner::getName(){return name;}
//--------------OTHERS-------------------//
Owner::Owner(std::string unsetName, int unsetOwnerAge){
Owner::getName();
Owner::getAge();
}
The problem here is that you don't have a constructor that receives 0 parameters.
You have 2 options:
1 - Define other constructor:
//header file
class Owner {
...
public:
Owner(std::string, int);
Owner();
...
};
//cpp file
...
Owner::Owner(){
name = "Jhon Doe";
age = 18;
}
...
2 - Define default params:
//header file
class Owner {
...
public:
Owner(std::string unsetName = "John Doe", int unsetAge = 18);
...
};
//cpp file
...
Owner::Owner(std::string unsetName = "John Doe", int unsetAge = 18);
Owner::getName();
Owner::getAge();
}
...
Note: I don't know why you are calling getter in the constructors.
Looks like your Owner class dosen't have a default constructor try including Owner::Owner() constructor.
I have two classes: SessionCardsMode and SetOfCards. SessionCardsMode takes in its constructor pointer to object of SetOfCards. When I try to create dynamically new SessionCardsMode object in SetOfCards method initializing it with this pointer I get information: "Cannot initialize type 'SessionCardsMode' with rvalue of type 'SetOfCards*'". It looks like I haven't proper constructor, but I have provided it. I don't know why it doesn't work. The problem is in SetOfCards::getSessionCards method in the first line of it. I've found that if I try to create the same object in body of class SessionCardsMode using identical statement everything works fine, but if I try to make it out of class I get the error.
//////////////////////////////SesionCardsMode.h
#pragma once
#include "Card.h"
#include "SetOfCards.h"
class SessionCardsMode
{
protected:
SetOfCards* m_setData;
std::forward_list<Card*> m_sessionSet;
public:
explicit SessionCardsMode(SetOfCards* set) : m_setData(set) {};
virtual Card* getCard();
//allows making combination of set setup by mixing classes that derives
//from ModeOfSet
void addAndShuffle(const SessionCardsMode* mode);
};
///////////////////////////////SetOfCards.h
#pragma once
#include "Card.h"
#include "SessionCardsMode.h"
class SetOfCards
{
private:
std::vector<Card> m_cardSet;
std::string m_setName;
public:
SetOfCards()=default;
explicit SetOfCards(std::string setName);
template<typename Iter>
SetOfCards(Iter begin, Iter end, std::string setName);
SessionCardsMode* getSessionCards(std::vector<CreatorAndInitVal> creators);
};
////////////////////////////////////////SetOfCards.cpp
#include "SetOfCards.h"
SessionCardsMode* SetOfCards::getSessionCards(
std::vector<CreatorAndInitVal> m_sessionCardsCreators)
{
SessionCardsMode* sessionCards=new SessionCardsMode(this); // error here
return sessionCards;
}
I don't understand why you don't get an error when you declare the constructor of SessionCardsMode (when you are compiling SetOfCards.cpp) - as far as I can see, at that point, SetOfCards is not defined.
Anyway, the solution to your problem is not to #include any of the headers in other headers, but to declare (not define) the other classes. So:
//////////////////////////////SesionCardsMode.h
#pragma once
class Card;
class SetOfCards;
class SessionCardsMode
{
protected:
SetOfCards* m_setData;
std::forward_list<Card*> m_sessionSet;
public:
explicit SessionCardsMode(SetOfCards* set) : m_setData(set) {};
...
};
///////////////////////////////SetOfCards.h
#pragma once
class Card;
class SessionCardsMode;
#include <vector> // You need this
#include <string>
class SetOfCards
{
private:
std::vector<Card> m_cardSet;
std::string m_setName;
public:
SetOfCards()=default;
explicit SetOfCards(std::string setName);
...
};
////////////////////////////////////////SetOfCards.cpp
#include "SetOfCards.h" // This should always be first
#include "..." // You'll probably need some more here.
SessionCardsMode* SetOfCards::getSessionCards(
std::vector<CreatorAndInitVal> m_sessionCardsCreators)
{
SessionCardsMode* sessionCards=new SessionCardsMode(this); // Error should be fixed
return sessionCards;
}
I'm a first-year college student that doesn't know everything about CS yet, so please bear with my newness to it, and this is my first question on here.
For an assignment, we are making faux version of Pokemon Go to practice using polymorphism in c++, and I'm running into some compiler errors. Here are the three files with just a sample of the code in them:
#ifndef EVENT_H
#define EVENT_H
#include <string>
#include "Trainer.h"
class Event{
protected:
std::string title;
public:
Event();
~Event();
virtual void action(Trainer) = 0;
};
#endif
Trainer.h:
#ifndef TRAINER_H
#define TRAINER_H
#include "Pokemon.h"
class Trainer{
private:
Pokemon* pokemon;
int num_pokemon;
public:
Trainer();
~Trainer();
//include accessors and mutators for private variables
};
#endif
Pokemon.h:
#ifndef POKEMON_H
#define POKEMON_H
#include "Event.h"
#include <string>
class Pokemon : public Event{
protected:
std::string type;
std::string name;
public:
Pokemon();
~Pokemon();
virtual bool catch_pokemon() = 0;
};
#endif
The trainer.h file is a parent class for each pokemon type (eg Rock) which just defines a few virtual functions. The error I'm getting is when I'm compiling all of this and I get something that says:
Pokemon.h : 5:30: error: expected class-name befoer '{' token:
class Pokemon : Event {
Pokemon need to be a derived class to an event, so that an event pointer can point in another Location class can point to either a pokemon, pokestop, or cave for the assignment, and I have been looking online for hours and can't figure out what to do. I would appreciate the help! Let me know if you need more info or something because again, this is my first time posting a question.
You need some forward declarations.
In Event.h, you can put class Trainer; instead of #include "Trainer.h". In Trainer.h, you can put class Pokemon; instead of #include "Pokemon.h".
You will probably need to include the appropriate headers in the corresponding source files in order to actually use the other classes. But by avoiding the includes in the header files, you get out of the circular dependency trouble.
Pokemon.h must continue to #include "Event.h", since you're inheriting Event, which requires a complete definition.
Use forward declaration, to tell classes the type they need to use will be defined later. You can use forward declaration in situations where the size is know, pointers and references are always the same size regardless of the type they point to so use them.
#ifndef EVENT_H
#define EVENT_H
#include <string>
class Trainer;
class Event
{
protected:
std::string title;
public:
Event();
virtual ~Event();
virtual void action(Trainer* const trainer) = 0;
};
#endif
then
#ifndef TRAINER_H
#define TRAINER_H
class Pokemon;
class Trainer
{
private:
Pokemon* const pokemon;
int numPokemon;
public:
Trainer();
~Trainer();
};
#endif
then
#ifndef POKEMON_H
#define POKEMON_H
#include "Event.h"
#include <string>
class Pokemon : public Event
{
protected:
std::string type;
std::string name;
public:
Pokemon();
virtual ~Pokemon();
virtual bool catchPokemon() = 0;
};
#endif
when using polymorphism (virtual functions) you must always make the base class destructor virtual too. It is also nice to make the derived classes destructor virtual as well, but it is not required.
This question already has answers here:
Resolve build errors due to circular dependency amongst classes
(12 answers)
Closed 8 years ago.
I have these two classes that need each other and inherited from the same class. Wehn I compile Seller.h, it compiles fine but when I compile Buyer.h I get errors from Seller.h.
So when i compile Buyer.h I get errors such as :
Seller.h:14:16: error: âBuyerâ has not been declared
void addBuyer(Buyer*);
^
Seller.h:15:14: error: âBuyerâ was not declared in this scope
std::vector<Buyer*> getBuyers() const;
Seller.h:20:17: error: âOrderâ has not been declared
void fillOrder(Order*);
^
They are #included but it still says out of scope.
#ifndef SELLER_H
#define SELLER_H
#include "Entity.h"
#include <string>
#include <vector>
#include "Inventory.h"
#include "Buyer.h"
#include "Order.h"
class Seller : public virtual Entity
{
public:
Seller(const std::string &, const std::string &, double=0.0);
virtual~Seller(){}
void addBuyer(Buyer*);
std::vector<Buyer*> getBuyers() const;
void setInventory(Inventory*);
Inventory* getInventory() const;
virtual void list() const override;
virtual void step() override;
void fillOrder(Order*);
private:
Inventory* inv;
std::vector <Buyer*> buyers;
};
#endif
Buyer.h
#ifndef BUYER_H
#define BUYER_H
#include <string>
#include "Entity.h"
#include <queue>
#include "Order.h"
#include "Seller.h"
class Buyer : public virtual Entity
{
public:
Buyer(const std::string &, const std::string &, double =0.0 );
virtual ~Buyer(){}
void addSeller(Seller *);
std::queue <Seller *> getSellers() const;
void addOrder(Order *);
std::queue <Order*> getOrders() const;
virtual void list() const override;
virtual void step() override;
private:
std::queue <Order*> orders;
std::queue <Seller*> sellers;
};
#endif
You have a cyclic dependency between Seller and Buyer. This will never work because the compiler requires the declaration of Seller in order to compile Buyer... yet it also requires the declaration of Buyer to compile Seller.
You can instead forward declare your classes because all you actually use are pointers to these types. For example:
#ifndef SELLER_H
#define SELLER_H
#include "Entity.h"
#include <string>
#include <vector>
#include "Inventory.h"
#include "Order.h"
// forward declaration of Buyer
class Buyer;
class Seller : public virtual Entity
{
public:
Seller(const std::string &, const std::string &, double=0.0);
virtual ~Seller(){}
void addBuyer(Buyer*);
std::vector<Buyer*> getBuyers() const;
void setInventory(Inventory*);
Inventory* getInventory() const;
virtual void list() const override;
virtual void step() override;
void fillOrder(Order*);
private:
Inventory* inv;
std::vector <Buyer*> buyers;
};
#endif
If you had an instance of Buyer as a member of Seller (i.e., Buyer _buyer;), or if any method took/returned an instance of Buyer, you would be forced to change your structure. Since you don't have that problem, a forward declaration will suffice.
As an aside, and admitting that I am not privy to the structure of your program, it is usually a bad sign when one sees so many naked pointers being used in a C++ program. You can store instances. You can use safe pointers (shared_ptr and unique_ptr) depending on your ownership semantics.
For example, addBuyer can easily take a Buyer& instead of a pointer. Now you don't have to worry about invalid pointers. I'm assuming that you add these to your buyers vector... but how are you guaranteeing that these pointers remain valid for the lifetime of a Seller instance? You can't; you're at the mercy of whomever called addBuyer.
Why not just store a std::vector<Buyer> and take a reference in your add method? Is the cost of a copy so prohibitive as to warrant this design? If so, could you not use shared_ptr?
Could anyone, please, explain what can cause this error?
Error: Invalid base class
I've got two classes where one of them is derived from second:
#if !defined(_CGROUND_H)
#define _CGROUND_H
#include "stdafx.h"
#include "CGameObject.h"
class CGround : public CGameObject // CGameObject is said to be "invalid base class"
{
private:
bool m_bBlocked;
bool m_bFluid;
bool m_bWalkable;
public:
bool draw();
CGround();
CGround(int id, std::string name, std::string description, std::string graphics[], bool bBlocked, bool bFluid, bool bWalkable);
~CGround(void);
};
#endif //_CGROUND_H
And CGameObject looks like this:
#if !defined(_CGAMEOBJECT_H)
#define _CGAMEOBJECT_H
#include "stdafx.h"
class CGameObject
{
protected:
int m_id;
std::string m_name;
std::string m_description;
std::string m_graphics[];
public:
virtual bool draw();
CGameObject() {}
CGameObject(int id, std::string name, std::string description, std::string graphics) {}
virtual ~CGameObject(void);
};
#endif //_CGAMEOBJECT_H
I tried cleaning my project but in vain.
It is not valid to define an array (std::string m_graphics[]) without specifying its size as member of a class. C++ needs to know the size of a class instance in advance, and this is why you cannot inherit from it as C++ won't know at runtime where in the memory the members of the inheriting class will be available.
You can either fix the size of the array in the class definition or use a pointer and allocate it on the heap or use a vector<string> instead of the array.