I am facing the following problem. I have the following classes, Room and Reservation . For Reservation class there is a function (void Reservation :: rsrvRoomAssignment(Room* r)) that assigns the Room* rsrvRoom member of Reservation class, to a Room object. I want though to call this class from inside the Room object but i have no clue on how to achieve that properly passing as argument the created object that runs the code.
The code describes the above:
Reservation.h
class Room;
class Reservation {
public:
static int rsrvCode;
string rsrvName;
unsigned int rsrvDate;
unsigned int rsrvNights;
unsigned int rsrvPersons;
Room* rsrvRoom; // Room assigned to reservation.
Reservation();
~Reservation();
void rsrvRoomAssignment(Room*);
};
Reservation.cpp
#include <iostream>
#include "Reservation.h"
using namespace std;
/*
Constructor & Destructor
*/
void Reservation :: rsrvRoomAssignment(Room* r){
rsrvRoom=r;
}
Room.h
#include "Reservation.h"
class Room {
public:
static unsigned int roomNumber;
unsigned int roomCapacity;
Reservation* roomAvailability[30];
double roomPrice;
Room();
~Room();
bool roomReservationAdd(Reservation*);
};
Room.cpp
#include <iostream>
#include <string>
#include "Room.h"
using namespace std;
/*
Constructor & destructor
*/
bool Room::roomReservationAdd(Reservation* r){
/* some statement that returns flase */
r->rsrvRoomAssignment(/* & of created object */); // This is the problem i described.
return 1;
}
I am pretty new to OOP so there might be some more logical errors on the above snipsets, so don't be harsh :) .
Thanks for any kind of help!
When inside a class method, this indicates the instance of the object calling it. In your case, when a room instance X calls X.roomReservationAdd(r),
this points to the room instance X.
Hence, you can simply call r->rsrvRoomAssignment(this);
Related
In a class, I have a member variable which is set when I call a method and am able to print it but it gets overridden when I try to print it a second time.
Below is the approximate code of whats happening.
nodezero.h
#ifndef NODEZERO_H
#define NODEZERO_H
//does nothing but sets three properties let say m_a, m_b and m_c.
#endif
nodefirst.h
#ifndef NODEFIRST_H
#define NODEFIRST_H
#include "nodezero.h"
class nodefirst {
public:
nodezero* root=nullptr;
void insert(int, int, int);
};
#endif
nodefirst.cpp
void nodefirst::insert(int a, int b, int c) {
nodezero realnode = nodezero(a,b,c);
nodezero* node = &realnode;
root = node;
return;
}
test.cpp
#include "nodezero.h"
#include "nodefirst.h"
#include <iostream>
using namespace std;
int main() {
nodefirst nf;
nf.insert(1,2,3);
cout<<nf.root->n_a<<"test"<<nf.root->n_a;
When the cout is called, part before "test" is printed correctly as 1 but after test is some garbage value.
Can someone please help me with this? I am not able to find what I am missing.
I need help with passing a function pointer on C++. I can't linkage one function for a class to other function. I will explain. Anyway I will put a code resume of my program, it is much larger than the code expose here but for more easier I put only the part I need to it works fine.
I have one class (MainSystem) and inside I have an object pointer to the other class (ComCamera). The last class is a SocketServer, and I want when the socket received any data, it sends to the linkage function to MainSystem.
ComCamera is a resource Shared with more class and I need to associate the functions ComCamera::vRecvData to a MainSystem::vRecvData or other function of other class for the call when receive data and send de data to the function class associate.
Can Anyone help to me?
EDDITED - SOLUTION BELOW
main.cpp
#include <iostream>
#include <thread>
#include <string>
#include <vector>
#include <cmath>
#include <string.h>
#include <stdio.h>
#include <exception>
#include <unistd.h>
using std::string;
class ComCamera {
public:
std::function<void(int, std::string)> vRecvData;
void vLinkRecvFunction(std::function<void(int, std::string)> vCallBack) {
this->vRecvData = vCallBack;
}
void vCallFromCamera() {
this->vRecvData(4, "Example");
};
};
class MainSystem {
private:
ComCamera *xComCamera;
public:
MainSystem(ComCamera *xComCamera) {
this->xComCamera = xComCamera;
this->xComCamera->vLinkRecvFunction([this](int iChannelNumber, std::string sData) {vRecvData(iChannelNumber, sData); });
}
void vRecvData(int iNumber, string sData) {
std::cout << "RECV Data From Camera(" + std::to_string(iNumber) + "): " << sData << std::endl;
};
};
int main(void) {
ComCamera xComCamera;
MainSystem xMainSystem(&xComCamera);
xComCamera.vCallFromCamera();
return 0;
}
Output will be:
MainSystem RECV Data From Camera(4): Example
You can have ComCamera::vRecvData be of type std::function<void(int, std::string)> and then have ComCamera::vLinkRecvFunction() be like this:
void ComCamera::vLinkRecvFunction(std::function<void(int, std::string)> callBack)
{
this->vRecvData = callBack;
}
and have MainSystem constructor be like this:
MainSystem::MainSystem(ComCamera *xComCamera)
{
using namespace std::placeholders;
this->xComCamera = xComCamera;
this->xComCamera->vLinkRecvFunction([this](int iNumber, std::string sData){vRecvData(number, sData);});
}
Still though the original question has way too much code to go through friend.
Here what you want :
#include<iostream>
using std::cout;
class A; //forward declare A
class B{
public:
void (A::*ptr)(int x); //Only declare the pointer because A is not yet defined.
};
class A{
public:
void increase_by(int x){
a+=x;
} // this function will be pointed by B's ptr
int a = 0; // assume some data in a;
B b; // creating B inside of A;
void analyze(int y){
(*this.*(b.ptr))(y);
} // Some function that analyzes the data of A or B; Here this just increments A::a through B's ptr
};
int main(){
A a; // creates A
cout<<a.a<<"\n"; // shows initial value of a
a.b.ptr = &A::increase_by; // defines the ptr that lies inside of b which inturns lies inside a
a.analyze(3); // calls the initialize method
(a.*(a.b.ptr))(3); // directly calls b.ptr to change a.a
cout<<a.a; // shows the value after analyzing
return 0;
}
Output will be :
0
6
I still don't get why would you do something like this. But maybe this is what you wanted as per your comments.
To know more read this wonderful PDF.
I don't know if I've missed something, but I can't seem to figure out how to make this work, and couldn't find the answer online.
Lets say I have a two classes, Class A, and Class B. (stored in separate files)
Class A has a function setName() that sets a variable within a Class A object.
Class B has a function setOtherName() that sets the value of a Class A object's name.
So I set setOtherName() up like so:
void setOtherName(ClassA& cla)
{
*cla.setName("foobar");
}
then my main script looks like so:
Class A burger;
Class B fries;
fries.setOtherName(*burger);
this does not work in my orignal script, I get the following error:
error: no matching function for call to 'ClassB::setOtherName(ClassA*&)
Any help is aprreciated! ( sorry for any confusion )
Actual code:
main.cpp:
#include <iostream>
#include "quests.h"
#include "player.h"
#include <string>
#include <cstdlib>
using namespace std;
int main()
{
quests GameQuests;
player Player;
GameQuests.quest1(Player);
Player.main();
return 0;
}
quests.cpp:
#include "quests.h"
#include "player.h"
#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
void quests::quest1(player& charact){
cout << "By the way, what was your name?" << endl;
person1=4;
system("pause");
charact->setName();
}
The implementation of your setOtherName function should have the signature
void ClassB::setOtherName(ClassA& cla)
You need to specify that it is included in ClassB. Within your class definition of ClassB, make sure to include
void setOtherName(ClassA&);
Furthermore, since your variable burger is of type ClassA and not of type ClassA*, there is no need to dereference the variable upon passing it into the function. Call it like
fries.setOtherName(burger);
You have also incorrectly dereferenced the variable cla. That object is passed by reference, not pointer, so there is no need to dereference.
You have to read about pointers and reference mate.
This is how your function should look like
void setOtherName(ClassA& cla)
{
cla.setName("foobar");
}
There is no need to deference something that is not a pointer.
ClassA burger;
ClassB fries;
fries.setOtherName(burger);
again, you don't need to dereference burger since its not a pointer.
If burger was created like this:
ClassA* burger = new ClassA();
and the function
void setOtherName(ClassA& cla)
was taking a reference, you had to dereference burger
fries.setOtherName(*burger);
Why are you derefrencing burger? You told the compiler to expect class A by reference, not by pointer.
Try:
fries.setOtherName(burger);
Also, get rid of the asterisk on setOtherName.
void setOtherName(ClassA & cla)
{
cla.setName("foobar");
}
EDIT:
Wrote a sample program of what I think you are trying to do below.
#include <iostream>
#include <string>
class Burger
{
public:
Burger(){}
void setName(std::string name){ m_name = name; }
std::string getName(){ return m_name; }
private:
std::string m_name;
};
class Fries
{
public:
Fries(){}
void setOtherName(Burger & burger){ burger.setName("FryBurger"); }
private:
};
int main()
{
Burger A;
Fries B;
B.setOtherName(A);
std::cout << A.getName() << std::endl;
return 0;
}
I'm new in C++ and I have something to do with a linked list, and I don't know why it doesn't work, need help from a prof :O)
Here's my .h
#ifndef UnCube_H
#define UnCube_H
using namespace std;
class ACube{
public:
ACube();
struct Thecube;
private:
void PrintList();
};
#endif
My ACube.cpp
#include <iostream>
#include "ACube.h"
ACube::ACube(){
};
struct Thecube{
int base;
int cube;
Thecube * next ;
};
void ACube::PrintList(){
};
and finally my main.cpp
#include <cstdlib>
#include <iostream>
#include "ACube.h"
using namespace std;
int main()
{
ACube * temp;
temp = (ACube*)malloc(sizeof(ACube));
for (int inc=1; inc <=20 ; inc++){
temp->ACube->nombrebase = inc;
temp->cube = inc*inc*inc;
}
system("PAUSE");
return EXIT_SUCCESS;
}
Everything was working fine, but when I add these lines :
temp->ACube->nombrebase = inc;
temp->cube = inc*inc*inc;
I add error saying :
'class ACube' has no member named 'TheCube'
'class ACube' has no member named 'cube'
Can someone help me because I want to create my list and fill the cube with number.
Other thing I want to use THIS. in the print,
Maybe someone can teach me what's wrong and how to do it !
Thanks for any help
You don't need to have a struct inside your class.
#ifndef UnCube_H
#define UnCube_H
using namespace std;
class ACube{
public:
ACube();
int base;
int cube;
ACube * next ;
private:
void PrintList();
};
#endif
ACube.cpp
#include <iostream>
#include "ACube.h"
ACube::ACube(){
};
void ACube::PrintList(){
};
Also, this string is wrong:
temp->ACube->nombrebase = inc;
it should be just:
temp->base = inc;
Last but not least, this code doesn't create a linked list, because you don't do anything with the ACube::next pointer.
There are so many horrible problems in your code, I suggest you should learn more C++ knowledge before writing linked list.
1. What is nombrebase?
I think nobody can answer.
2. You must allocate C++ class by new key word instead of malloc.
new invokes not only allocation but also class constructor, while malloc allocates only.
3. Thecube should been defined inside ACube
Since the code in your main() refers the member cube in class Thecube, main() must know what it is.
4. The member next in class ACube is a pointer which points to what?
What does a pointer point to without initilization? You should initial it in constructor, and destroy it in destructor.
5. temp->ACube
ACube is a class type, you can access member object, but not a type.
6. Never using namespace into a header file
It would make the client of header file has name collision.
The following is the corrected code. Just no compile error and runtime error, but this is NOT linked list:
ACube.h
#ifndef UnCube_H
#define UnCube_H
class ACube{
public:
struct Thecube
{
int base;
int cube;
Thecube * next;
};
ACube();
~ACube();
Thecube *next;
private:
void PrintList();
};
#endif
ACube.cpp
ACube::ACube()
: next(new Thecube)
{
}
ACube::~ACube()
{
delete next;
}
void ACube::PrintList(){
}
main.cpp
#include <cstdlib>
#include <iostream>
#include "ACube.h"
using namespace std;
int main()
{
ACube * temp;
temp = new ACube;
for (int inc = 1; inc <= 20; inc++)
{
temp->next->base = inc; // <-- This is not linked list, you shall modify.
temp->next->cube = inc*inc*inc; // <-- This is not linked list, you shall modify.
}
system("PAUSE");
return EXIT_SUCCESS;
}
I need to call a method from one class in the constructor of another class. I am not sure how to do this without getting a "was not declared in this scope" error. Note I am just learning C++.
See the comments in symboltable.cpp for what I am trying to accomplish here. I am not looking for anyone to do it for me. I could use an example or pointed in the right direction so I can figure this out.
symboltable.h code:
class SymbolTable
{
public:
SymbolTable() {}
void insert(string variable, double value);
void insert(string variable); // added for additional insert method
double lookUp(string variable) const;
void init(); // Added as mentioned in the conference area.
private:
struct Symbol
{
Symbol(string variable, double value)
{
this->variable = variable;
this->value = value;
}
string variable;
double value;
};
vector<Symbol> elements;
};
symboltable.cpp code:
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
#include "symboltable.h"
/* Implementing the "unreferenced variable" warning.
* Modify the symbol table by adding another insert method
* that supplies only the variable name.
* This method should be called when the variable name
* is encountered while building the arithmetic expression tree.
* It would be called in the constructor of the Variable class.
* The existing insert method, which is called when an assignment is encountered,
* would first check to see whether it is already in the symbol table.
* If it is not, then it is unreferenced.
*/
void SymbolTable::insert(string variable, double value)
{
/* This existing insert method, which is called when an assignment is encountered,
* first needs to check to see whether it is already in the symbol table.
* If it is not, then it is unreferenced.
* */
//Need to check if variable is in the expression need to find out how the expression is stored!
if (find(elements.begin(), elements.end(), variable)) {
const Symbol& symbol = Symbol(variable, value);
elements.push_back(symbol);
} else
throw string("Error: Test for output");
}
/* Adding another insert method that supplies only the variable name.
* This method should be called when the variable name is encountered
* while building the arithmetic expression tree.
* It should be called in the constructor of the Variable class.
*/
void SymbolTable::insert(string variable)
{
const Symbol& symbol = Symbol(variable, symbolTable.lookUp(variable));
elements.push_back(symbol);
}
double SymbolTable::lookUp(string variable) const
{
for (int i = 0; i < elements.size(); i++)
if (elements[i].variable == variable)
return elements[i].value;
else
throw "Error: Uninitialized Variable " + variable;
return -1;
}
void SymbolTable::init() {
elements.clear(); // Clears the map, removes all elements.
}
variable.h code:
class Variable: public Operand
{
public:
Variable(string name) //constructor
{
// how do i call symbolTable.insert(name); here
// without getting 'symboleTable' was not declared in this scope error
this->name = name;
}
double evaluate();
private:
string name;
};
variable.cpp code:
#include <string>
#include <strstream>
#include <vector>
using namespace std;
#include "expression.h"
#include "operand.h"
#include "variable.h"
#include "symboltable.h"
extern SymbolTable symbolTable;
double Variable::evaluate() {
return symbolTable.lookUp(name);
}
There are two solutions:
You use a global variable - like your Variable::evaluate() example. You can of course add your Variable::Variable() as a function in "variable.cpp" instead of the header. Or you can just put a extern SymbolTable symbolTable to the file "variable.h".
You pass in a reference to symbolTable into the constructor (and perhaps store that inside the Variable object - that way, symbolTable doesn't need to be a global variable at all.
By the way, it's generally considered bad style to add using namespace std before header files.
extern SymbolTable symbolTable; needs to go into the header file that is included by everyone who needs symbolTable. Then, in variable.cpp, you need to have SymbolTable symbolTable;
You need to instantiate the second class, either within the constructor, which will make it and its members available only within the constructor of the first class, or in the global namespace. For example:
MyFooClass CFoo;
MyBarClass CBar;
MyFooClass::MyFooClass()
{
CBar = new MyBarClass();
CBar.BarClassMemberFunction();
}