I've got a base class Container with a derived class Player_Inventory. There can only be one Player_Inventory so my code throws an exception if for some reason a second one is created.
The problem I'm having is that my code is failing my test as it throws the exception even on what is supposed to be the very first construction of the Player_Inventory class. I've debugged the code and two things are happening which I don't quite understand - the number attribute is not tracked by the debugger (at least not in the GUI on VSC), and it seems that right after hitting the first REQUIRE statement, the constructor is called again, thus triggering the exception.
Can anyone help?
After rewriting my constructor method, I'm still getting a similar error.
My revised code is as follows:
containers.h
#include<iostream>
#include<string>
#include<vector>
class Item { // Placeholder class for items
public:
std::string name;
Item(std::string n) : name{n} {};
};
class Container {
protected:
std::string name;
std::string description;
std::vector<Item> contents;
public:
Container(std::string, std::string);
std::string get_name() {return name;}
std::string get_description() {return description;}
std::vector<Item> get_contents() {return contents;}
};
containers.cpp (there are more methods defined in this file which aren't used here)
#include<iostream>
#include<string>
#include "containers.h"
Container::Container(std::string n, std::string desc) : name{n}, description{desc} {};
player_inventory.h
#include "containers.h"
class Player_Inventory : public Container {
public:
static int number;
Player_Inventory(std::string, std::string);
};
player_inventory.cpp
#include<iostream>
#include<stdexcept>
#include "player_inventory.h"
Player_Inventory::Player_Inventory(std::string n, std::string desc): Container(n, desc) {
number += 1;
if (number > 1){
throw std::invalid_argument("You can only have one inventory!");
}
};
int Player_Inventory::number = 0;
test_file.cpp
#include "../lib/Catch2/catch.hpp"
#include "player_inventory.h"
#include<iostream>
#include<string>
#include<vector>
SCENARIO("A player can have an inventory.") {
WHEN("A player inventory is created.") {
Player_Inventory myInventory("My Inventory", "Inventory for the player");
THEN("The created inventory has the correct attribute values.") {
REQUIRE(myInventory.get_name() == "My Inventory");
REQUIRE(myInventory.get_description() == "Inventory for the player");
REQUIRE(myInventory.get_contents().empty());
} // The code works fine when only up to here is included
AND_THEN("Only one player inventory can exist.") { // as soon as this line is included it tries to create another player_inventory object, causing the fail
REQUIRE_THROWS((Player_Inventory myOtherInventory("Second Inventory", "Testing for another one"))); // These two lines were not included but I've included them here as this is the test I wanted to run
REQUIRE(myInventory.get_number() == 1);
}
}
}
Not sure if related, but that's how you should call the Base constructor:
Player_Inventory(std::string n, std::string desc) : Container(n, desc) {
}
Related
#include <iostream>
#include <vector>
using namespace std;
class Test
{
private:
int ID;
string name;
public:
Test(int ID, string name);
};
Test::Test(int ID, string name)
{
this->ID = ID;
this->name = name;
}
int main()
{
vector<Test *> test_vect;
Test *ptr = new Test(100, "John");
test_vect.push_back(ptr);
cout << ptr->ID << endl;
return 0;
}
This is a simple code I'm trying.
I want to access to the data that I stored in vector.
I thought it would be accessible by using -> just like vector of struct but I can't. So I want to know how to load the data in class.
In addition, I thought sending data to heap section using new would make it accessible at any time I want regardless of whether it is private or public, but it seems like it is not possible.
Can you explain how it works?
(I don't even fully understand how class work, so detailed explanation would be very appreciated. Thx!)
A private variable cannot be accessed by code outside the class definition. (There are exceptions with friend)
ptr->ID does not work because main is outside the class definition.
This can be fixed by using a getter method.
#include <iostream>
#include <vector>
using namespace std;
class Test
{
private:
int _ID;
string _name;
public:
int ID() {return _ID;}
string name() {return _name;}
Test(int param_ID, string param_name);
};
Test::Test(int param_ID, string param_name)
{
_ID = param_ID;
_name = param_name;
}
int main()
{
vector<Test *> test_vect;
Test *ptr = new Test(100, "John");
test_vect.push_back(ptr);
cout << ptr->ID() << endl;
return 0;
}
The above example shows the getter methods ID() and name() which return the data members _ID and _name respectively.
ID() is allowed to access _ID because ID() is part of the class definition. name() is allowed to access _name because name() is part of the class definition.
Note: I would still consider this code to be flawed because it creates a new object on the heap, but does not delete it. You should also look up the keywords new and delete to see how they operate together.
I have 2 classes. Since Doctor will be considered as Employee, I should be using Employee class functions in Doctor class. Only extra thing that Doctor class has is TITLE. Basically, What I tried is I wanted to send value to Doctor's constructor,set title then send remained value to Employee's class ;however, I could not. This is what I have done so far,
employee.h
#ifndef EMPLOYEE_H
#define EMPLOYEE_H
class Employee {
private:
int ID;
char *firstname;
char *lastname;
int telno;
char *adress;
char *mail;
int salary;
public:
Employee();
Employee(int,char *,char*,int,char*,char*,int);
char* getfmame();
char* getlname();
char* getadress();
char* getmail();
int getID();
int gettel();
int getsalary();
void printall();
};
#endif
Employee.cpp
#include <iostream>
#include "employee.h"
using namespace std;
Employee::Employee() {
firstname = "Empty";
ID=0;
firstname="Empty";
lastname="Empty";
telno=0;
adress="Empty";
mail="Empty";
salary=0;
}
Employee::Employee(int id,char * first,char* last,int tell,char* adres,char* email,int salar){
ID=id;
firstname=first;
lastname=last;
telno=tell;
adress=adres;
mail=email;
salary=salar;
}
char* Employee::getfmame(){ return firstname; }
char* Employee::getlname(){ return lastname; }
char* Employee::getadress(){ return adress; }
char* Employee::getmail(){ return mail; }
int Employee::getID(){ return ID; }
int Employee::gettel(){ return telno; }
int Employee::getsalary(){ return salary; }
void Employee::printall(){
cout<<endl<<"EMLOYEE INFORMATION"<<endl<<"------------------"<<endl;
cout<<endl<<"ID :"<<ID<<endl<<"FIRST NAME: "<< firstname <<endl<<"LAST NAME: "<< lastname << endl << "TELEPHONE NUMBER: "<<telno<<endl<<"ADRESS: "<<adress<<endl<<"MAIL: "<<mail<<endl<<"SALARY: "<<salary<<endl;
}
Doctor.h
#ifndef DOCTOR_H
#define DOCTOR_H
#include "Employee.h"
using namespace std;
class Doctor :Employee {
public:
enum title {Intern=0,Practitioner=1,Assistant=2,Specialist=3,Docent=4,Professor=5,None=6};
Doctor();
Doctor(title a,int id,char * first,char* last,int tell,char* adres,char* email,int salar);
};
#endif
Doctor.cpp
#include <iostream>
#include "Doctor.h"
#include "Employee.h"
using namespace std;
Doctor::Doctor() {
title tit = None ;
}
Doctor::Doctor(title a,int id,char * first,char* last,int tell,char* adres,char* email,int salar) {
title tit=a;
Employee(id,first,last, tell,adres,email,salar);
printall();
cout<<"typed";
}
Main.cpp
#include <iostream>
#include "employee.h"
#include "doctor.h"
using namespace std;
int main(){
Doctor a=Doctor(Doctor::None,12,"a","b",0550550505,"8424 str nu:5","#hotmail",5000);
return 0;
}
Subclass construction in C++ works so that the base class object must be constructed when the subclass' constructor body is executed:
class A {
/* etc. etc. */
public:
void do_stuff();
};
class B : public A {
B() {
// at this point, an A has already been constructed!
A::do_stuff();
}
};
Note that in this example, since we haven't chosen an explicit constructor for the A instance, the default constructor, A::A(), will be used; and if that constructor is unavailable - we get a compilation error. The fact that a constructor for A has been called is what allows us to then use methods of class A - like A::do_stuff() in the example above.
But - how can we specify a different constructor before the body of the B constructor? Or in your case, how can we use the appropriate constructor for Employee before the body of the Doctor constructor?
The answer was suggested by #user4581301: You need to use an member initializer list. Initializations/constructions on this list are performed before the body, and may include the underlying class. I'll demonstrate with a simplified example. Let's suppose an Employee only has an id and a Doctor only has an additional title.
class Employee {
protected:
int id_;
public:
Employee(int id) : id_(id) { };
int id() const { return id_; }
};
class Doctor : public Employee {
protected:
std::string title_;
public:
Doctor(int id, std::string title) : Employee(id), title_(title) { };
const std::string& title() const { return title_; }
};
So, when a Doctor is being constructed, it constructs its underlying Employee instance using the id it got. The constructor body is used for more complex code beyond simple member initializations.
PS:
You might want to initialize the title_ member with std::move(title) rather than just title, see this question for details.
It's confusing when a constructor has more than two or three parameters with compatible types - users are likely to confuse them with each other. You might consider default values for most fields and setting them after construction, or alternatively, using a builder pattern.
address, with two d's, not adress.
Unless you plan on editing char* fields in-place, use const char *.
They way you've written your classes, Doctor methods would not have write acesss to Employee methods; make sure that's what you intended.
I have some other nitpicks but I'll stop now...
This question already has answers here:
Why does the C++ map type argument require an empty constructor when using []?
(6 answers)
Closed 5 years ago.
I've done a lot of Googling and can't seem to figure out what's going on. I'm teaching myself C++ (I'm more familiar with Java).
I have Item Class objects that are being stored in an Inventory Class map, not as pointers. I want to retrieve one of the items from the Inventory in a function, assign it to a temp variable while I delete it from the Inventory map, and then return the object itself so something else can use it. When I originally tried using the code within my function it was returning the error (followed by the stack trace of c++ library stuff):
no matching constructor for initialization of 'Item'
::new ((void*)__p) _Tp();
I tried creating a copy constructor, but to no avail. Eventually, it worked by including an empty constructor ( Item(); ) in my header file and defining it in my cpp file ( Item::Item() {} ).
I would just like to understand why this was necessary so I can recognize it in the future to know what I'm doing.
EDIT: Upon further inspection of the error stack trace, it turned out the actual problem with with the Inventory::addItem function. When assigning an object to a map using operator[], the map first instantiates the value type to the key using the default constructor before making the assignment. No default constructor was available, so the error was returned.
It was fixed by changing the line to map.insert({key, value})
Here are the important parts of the two class files:
//item.h
#include <string>
using namespace std;
class Item {
private:
string name;
int type;
int levelReq;
public:
Item(string name, int type, int levelReq);
Item();
string getName() {return name;}
int getType() {return type;}
friend ostream &operator<<(ostream &out, const Item &item);
};
---------------------------------------------------------------
//item.cpp
#include <string>
#include "item.h"
using namespace std;
Item::Item(string n, int t, int l) : name(n), type(t), levelReq(l) {}
Item::Item() {}
ostream &operator<<(ostream &out, const Item &item) {
return out << item.name;
}
---------------------------------------------------------------
//inventory.h
#include <map>
#include "item.h"
class Inventory {
private:
map <int, Item> inventory;
int size;
bool full;
int nextFree;
void findNextFree();
public:
Inventory();
bool isFull() {return full;}
void addItem(Item item);
Item getItem(int slot);
void showInv();
};
---------------------------------------------------------------
//inventory.cpp
#include <iostream>
#include <string>
#include "inventory.h"
#include "item.h"
using namespace std;
Inventory::Inventory() {
full = false;
nextFree = 1;
size = 28;
}
void Inventory::addItem(Item item) {
if (!full) {
inventory[nextFree] = item;
findNextFree();
}
else {
cout << "Your inventory is full (Inv::addItem)";
}
}
Item Inventory::getItem(int slot) {
Item item = inventory.at(slot);
inventory.erase(slot);
full = false;
if (nextFree > slot) {
nextFree = slot;
}
return item;
}
void Inventory::findNextFree() {
nextFree++;
if (nextFree == size + 1) {
full = true;
}
else if (inventory.count(nextFree)) {
findNextFree();
}
}
I think the issue rose because you declared a constructor for your item class.
C++ will automatically generate the necessary constructors if you don't provide any custom constructors.
The necessary constructors are the default, copy and move constructors.
The moment you provide one, the default constructors won't be generated and you have this issue. This principle will also apply to structs.
Check the reference to see for yourself:
http://en.cppreference.com/w/cpp/language/default_constructor
http://en.cppreference.com/w/cpp/language/copy_constructor
http://en.cppreference.com/w/cpp/language/move_constructor
Hope this answers your question.
I got two classes, one named Person that I checked is working (I can create objects of that class so the problem should not be here).
I then have another class called Family with composition from Person:
Family.h
#include "Person.h"
class Family
{
public:
Family();
void printFamily();
private:
Person dad_();
Person mum_();
Person son_();
Person daughter_();
};
Family.cpp
#include "Family.h"
Family::Family()
{
}
void printFamily()
{
dad_.printAll();
mum_.printAll();
son_.printAll();
daughter_.printAll();
//printAll() is a function in the Person class that worked when
//I tested it earlier with only the person class
}
But when i try to compile this I get an error:
left of '.printAll' must have class/struct/union
'son_' : undeclared identifier
This error goes for all the .printAll() calls in family.cpp.
I can't see why this wouldn't work, so I hope you can.
Edit1:
Ok i changed
void printFamily()
to
void Family::printFamily()
That removes one error, but i still get
left of '.printAll' must have class/struct/union
Edit2
Ah my bad with the Person calls i changed them to
Person dad_;
and the same with the rest.
Seems like their might be an error with my Person class so i will post that also
Person.h
#include <string>
using namespace std;
class Person
{
public:
Person( const string & = "000000-0000", const string & = "N", const string & = "",const string & = "N");
~Person();
void setFirstName(const string &);
void setMiddleName(const string &);
void setLastName(const string &);
void getData(string &,string &,string &,string &);
static int getNumberOfPersons();
void printPartially() const;
void printAll() const;
bool checkForSameName(const Person &);
private:
string firstName_;
string middleName_;
string lastName_;
string socialSecNumber_;
static int numberOfPersons_;
};
Person.cpp
#include "Person.h"
#include <iostream>
int Person::numberOfPersons_ = 0;
Person::Person( const string &sNumber, const string &firstName, const string &middleName,const string &lastName )
:firstName_(firstName),middleName_(middleName),lastName_(lastName),socialSecNumber_(sNumber)
{
numberOfPersons_ ++;
}
Person::~Person()
{
numberOfPersons_--;
}
void Person::setFirstName(const string &firstName)
{ firstName_ = firstName; }
void Person::setMiddleName(const string &middleName)
{ middleName_ = middleName; }
void Person::setLastName(const string &lastName)
{lastName_ = lastName;}
void Person::getData(string &fName,string &mName,string &lName,string &sNumber)
{
fName = firstName_;
mName = middleName_;
lName = lastName_;
sNumber = socialSecNumber_;
}
int Person::getNumberOfPersons()
{
return numberOfPersons_;
}
void Person::printPartially() const
{
cout <<"Navn: "<<firstName_<<" "<<middleName_<<" "<<lastName_<<endl;
cout <<"Født: ";
for (int i = 0;i<6;i++)
{
cout <<socialSecNumber_.at(i);
}
}
void Person::printAll() const
{
cout <<"Navn: "<<firstName_<<" "<<middleName_<<" "<<lastName_<<endl;
cout <<"Personnr: "<<socialSecNumber_<<endl;
}
bool Person::checkForSameName(const Person &p)
{
if (p.firstName_ == firstName_ && p.middleName_ ==middleName_ && p.lastName_ == lastName_)
return true;
else
return false;
}
Now i am getting some new errors:
error C2011: 'Person' : 'class' type redefinition
see declaration of 'Person'
'Family::dad_' uses undefined class 'Person'
The "dad" error applies to the whole family
You have a few syntax issues.
First, you're declaring each of what are supposed to be member variables as functions which return Person. They should look like (note, no parens):
Person dad_;
Person mum_;
Person son_;
Person daughter_;
You're also missing the scoping on your definition of printFamily:
void Family::printFamily() {
...
}
Without the preceding Family::, C++ thinks you're defining a free function, and doesn't know to look inside the Family class for the declarations of dad_, mum_, etc.
Additionally, at least with the code you've shown, there's no way to initialize the people in your class. The Family constructor should take arguments to define the people, or you should have setters which allow defining them later. Right now, you'll get 4 identical people, set up however the default person constructor builds them.
I would normally prefer the constructor method, but I have other design reservations about your code to begin with (e.g. Does a family always contain mum, dad, brother, sister?) and that's not really what this question is about.
The line:
Person dad_();
says that dad_ is a function that returns a Person, not an object. Did you mean that? Similarly for others.
Try
Person dad_;
Family.h
#include "Person.h"
class Family
{
public:
Family();
void printFamily();
private:
Person dad_;
Person mum_;
Person son_;
Person daughter_;
};
Family.cpp
#include "Family.h"
Family::Family()
{
}
void Family::printFamily()
{
dad_.printAll();
mum_.printAll();
son_.printAll();
daughter_.printAll();
//printAll() is a function in the Person class that worked when
//I tested it earlier with only the person class
}
The out of line definition of a member function needs to include the class name:
void Family::printFamily()
{
//...
Surprisingly, you already got this right for the constructor but then immediately forgot...
Second, your private class members are functions, not data members (which is odd), but if that's deliberate, you need to call them:
dad_().printAll();
// ^^^
We are making a list that hold info on boardgames (name, year, score). We scan the info out of a .csv file, make a struct based on that info and then add the struct to a list. We keep doing this untill the document is done reading. Problem is that the push_back method of the list doesn't work. Here's the header of the list class:
NOTE BoardGame is the custom struct. BoardGame(wstring name, int year, float score).
#pragma once
#include "GameEngine.h"
#include "BoardGame.h"
#include <list>
class BoardGameList
{
public:
BoardGameList() {}
virtual ~BoardGameList() {}
// Methods
void Load(const tstring& fileName);
// Members
private:
std::list<BoardGame> m_Games;
};
The cpp file. Maybe I made the list the wrong way?
#include "BoardGameList.h"
#include <fstream>
void BoardGameList::Load(const tstring& fileName)
{
tifstream file(fileName);
tstring line;
if(!file)
{
GAME_ENGINE->MessageBox(_T("Error: The file could not be found!"));
}
else
{
tstring name;
tstring year;
tstring score;
while(!(file.eof()))
{
getline(file,line);
year = line.substr(0,4);
score = line.substr(5,5);
name = line.substr(11,line.find(_T("\n")));
float numberScore = std::stof(score);
int numberYear = std::stoi(year);
m_Games.push_back(BoardGame(name,numberYear,numberScore));
}
}
}
Running the program triggers an error (unhandled exception) that leads me to the following code in the "list" class itself I think.
_Unchecked_iterator _Unchecked_end()
{ // return unchecked iterator for end of mutable sequence
return (_Unchecked_iterator(this->_Myhead, this));
}
Any ideas why I can't add stuff to my list? I tried adding something in the constructor to check if it maybe needed an element before I could add more but even then, using a breakpoint showed me that the memory could not be read.
Many thanks in advance.
EDIT: Header of BoardGame
#pragma once
#include "GameEngine.h"
struct BoardGame
{
BoardGame(tstring name, int year, float score);
//Methods
tstring operator<<(BoardGame rhs);
//Members
tstring m_Name;
int m_Year;
float m_Score;
};
What exception is being thrown? This is vital to debugging your problem.
Without that information my best guess is this line:
name = line.substr(11,line.find(_T("\n")));
Will throw an exception on any line without a trailing newline, or any line less than 11 characters long.