From parent class, I mean the class whose obj has been made in the class after that.
#include <iostream>
using namespace std;
class a{
int x,y;
public:
a(int u = 0, int v = 0);
void setXY(int,int);
[code].....
I am currently having an issue with a piece of code that I am writing in which I need to use a vector of a child class as a parameter in a function in the parent class. Below is an example of my code:
#include "child.h"
#include <vector>
class parent {
parent();
function(std::vector<child> children);
// rest of class here
}
When I do this my program doesn't compile. However if I try to forward declare, as shown in the following example, it once again refuses to compile:
#include <vector>
class child;
class parent{
parent();
function(std::vector<child> children);
// rest of class here
}
This time, it refuses to compile because it needs to know the full size of the class child in order to create the vector. How to being able to access the child is essential for my program, so what should I do?
In this assignment the student should develop a month calendar by designing a class called calendarType . This class uses two other classes (dateType and dayType) as described below:
1. dayType Class: This class has been designed by students in Lab1 exercises. Referee to it.
2. dateType Class: This class is designed and implemented to keep track of data. This class has been provided it to you. Study it first then add definitions and implementations of the following operations to this class:
- Test whether the year is a leap year. Leap year is identified by 3 criteria :
- The year is evenly divisible by 4;
- If the year can be evenly divided by 100, it is NOT a leap year, unless;
- The year is also evenly divisible by 400. Then it is a leap year.
- Return the number of days in the month. For example, if the date is 12/3/2014, the number of days to be returned is 31 because there are 31 days in March.
- Return the number of days passed in the year. For example, if the date is 18/3/2014 the number of days passed is 77. Note that the number of days returned also includes the current day.
- Return the number of days remaining in the year. For example, if the date is
18/3/2014 , the number of days remaining in the year is 288.
- Calculate the new date by adding a fixed number of days to the date. For example, if the date is 18/3/2014 and the days to be added are 25, the new date is 12/4/2014.
To print monthly calendar using calendarType class, you must know the first day of the month and the number of the days in that month. Thus, you must store the first day of the month, which is in the form of dayType and the month and the year of the calendar. Clearly, the month and the year can be stored as an object of the form dateType by setting the day component of the date to 1, and the month and year as specified by user.
Design the class calendarType so that the program print a calendar for any month starting 1/1/ 1500 which is Monday. To calculate the first day of a month, you can add the 2 appropriate days to Monday of January 1, 1500. For this class identify and implement the following operations:
- Determine the first day of the month for which the calendar will be printed. Call this operation firstDayOfMonth.
- set/get month.
- set/get year.
- Print calendar for particular month.
- Add the appropriate constructors to initialize the member variables.
- Write a test program to print the calendar for either a particular year or a particular month.
In the project I'm currently working on I define a class that only inherits from a parent class and takes one argument.
Does this class need to be defined in the header or source file? I read different answers around the internet.
Or is it better to always split definition and logica, even for something like an operator?
Firstly I don't really know if this is possible.
This is my Class Diagram: [URL]...
github: [URL]...
I want to redefine the price object of the Book Class. However price is defined at Products Class.
I want the price value change according to the marker value, which is a Book attribute.
If the marker is blue, price gets a value of 10 (e.g.), if it has another value, price is equal to 20.
Below is simplified code consists of two classes, namely Parent and Child.
Child is inherited from Parent.
All member functions of class Parent are declared virtual, and they have been overridden in the class Child.
Code 1:
#include <cstdlib>
#include <iostream>
using namespace std;
#define QUANTITY 5
class Parent {
[Code] ....
The output of the code:
Child::showID() -- ID is 1804289383
Child::showID() -- ID is 846930886
Child::showID() -- ID is 1681692777
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1957747793
Parent::operator=() invoked.
Child::showID() -- ID is 1804289383
Child::showID() -- ID is 846930886
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1714636915
Child::showID() -- ID is 1957747793
Question:
Why is Parent::operator= invoked instead of Child::operator= ..?
Isn't it already declared virtual and hence would be overridden..?
I need to invoke Child::operator= instead. How to achieve this?
I am doing C++ data structures exercises, and I am still learning some of the more basic concepts. I have a parent class:
template<class T>
class linkedListType {
public:
protected:
int count;
nodeType<T> *first;
nodeType<T> *last;
private:
};
Derived class:
#include "linkedListType.h"
template<class T>
class orderedLinkedList: public linkedListType<T> {
public:
void mergeList(orderedLinkedList<T> &list1, orderedLinkedList<t> &list2) {
first = list1.first;
...
} private:
};
There is more code in my mergeList() function, but I included the line that is giving me problems. The error that my CodeBlocks compiler is giving me is that 'first' was not declared in this scope.
Strangely enough, if I change it to this->first, the error disappears.
1. Why does it not recognise 'first'?
2. Why would this->first work at all? Is the 'this' object a smart pointer?
In my program, I create controls by deriving base objects of them I've made. These controls are then are attached within the OnCreate() function via a method I've created. For example:
Code:
class tChat: public TextBox {
public:
void OnKeyDown(UINT &KeyCode) {
if (KeyCode == VK_RETURN) {
MessageBox(NULL, "Pressed enter!", NULL, 0);
[Code] ....
The use of AddControl() feels quite redundant and is only their to parse a pointer to txtChat's Parent. I'm trying to see if it's possible to remove this line and automatically associate txtChat to fMain.
Currently my hierarchy looks like:
[User's derived Form] -> [MDIForm or Form] -> [FormBase] -> [Object]
[User's derived Control] -> [TextBox, etc..] -> [Control] -> [Object]
The user can then derive the Form and Controls and use their virtual OnEVENT functions to handle all the messages they expose.
So far my first concept is using the order-of-creation based on base-class constructor's being fired to determine which object is associated with what.
If I create a copy of a class (i.e. a Form-derived object), first the Form's constructor is fired, and then the constructor's of any class-based member-variables are fired. Is this a safe assumption? I imagine the only time this could be affected is by another thread creating the object of a Form or Control derivative?
If this assumption is true, I could save the 'this' pointer from the FormBase constructor, and then associate it with each Control via the base Control class' constructor? Then to ensure thread-safety, I could map the current FormBase pointer to the local thread id to ensure no conflict if multiply threads are creating forms at the same time?
I've created some mock-up code before trying to implement this into my main code. The following keeps track of the current Form being created by using a ThreadId-based map. When a control is created it gets the FormBase pointer based of it's ThreadId calling. The control then calls an Attach() function of it's parent Form using the pointer it just got, and parses a pointer to the control. The Form then adds the control's pointer to a list. When the Form eventually parses WM_CREATE, it automatically pulls the controls from the list and fires their virtual Create() functions to build them.
Mock-up:
Code:
#include <Windows.h>
#include <string>
#include <map>
#include <list>
class FormBase;// Forward declaration
class FormMap;// Forward declaration
class Object {};// Base Object
[Code] ....
Is this plausible to use? I imagine C++ does not have many "guarantees" about how it creates objects and when. But I thought it would be safe that it would never create member-variables before the class of them is first created?
This keeps giving me the error
ecg.h:18:11: error: field "next" has incomplete type
How do I do what I need? It does the same thing whether I use a class or a struct. This is C++ code
struct ECG_node {
double voltage;
clock_t time;
ECG_node next;
[Code] .....
I am making a very basic parent/child class based program that shows polymorphism. It does not compile due to a few syntax errors reading "function call missing argument list. Lines 76 and 77, 81 and 82, and 86 and 87.
#include<iostream>
using namespace std;
class people {
public:
virtual void height(double h) = 0;
virtual void weight(double w) = 0;
[Code] ....
I got a code of a BST and i need to create a function that will return the value of the parent that it's son/sons sum to the biggest sum - BST and not AVL.
I assume that the shortest code will be recursive but i didn't manage to get it right - i'll send the code without my function because it's wrong - l
#include <vector>
#include <iostream>
using namespace std;
//-----------------------------------------------------------------
// class Node
// a single Node from a binary tree
//-----------------------------------------------------------------
template <class T> class Node
[Code] ....
Let's say I have a variadic type A and a non-variadic type B:
Code:
template <typename ... Args>
class A
{};
template <typename T>
class B
{};
Now, I'd like to do the following (pseudocode since I don't know how to do this yet):
Code:
template <typename ... Args>
class C: public A<B<Args1>,B<Args2>,B<Args3>....>
{};
Essentially, I'd like to take the parameter pack used for C and compose B around each element individually, then pass the result to A.
how I can do this?
So lately I've been writing multiple header and cpp files and I would always the same error when I finally #include headers in my main.cpp. This error
Code:
undefined reference to `...`
On Youtube videos I see people doing this and their work magically compiles correctly. I found out that when I #include the headers' cpp files instead, my programs would compile. I use Code::Blocks with GNU GCC compiler.
I have a question regarding composition and accessing members "deep" inside the composed structure. For example;
class A {
private:
int m_myInt;
public:
int myInt() const {return this->m_myInt;};
void myInt(int newInt) {this->m_myInt = newInt;};
[Code] ....
Now, from somwhere I have access to an object of type B where I want to update the A::m_myInt. How would you do this without "breaking" the whole purpose of private/public members?
B myB;
myB.m_a.myInt(3); // Not allowed, and not desireable
I thought about implementing access through functons kind of like;
A & B::a() {return this->m_a;};
myB.a().myInt(3);
but I'm worried that this exposes my B::m_a-object too much. This would allow
myB.a() = A();
, right?
The following is a more desireable way of acces, but doesn't work for updating;
A const & B::a() {return this->m_a;};
myB.a().myInt(3); //Disallowed? myInt(int) is non-const.
What about this? Is this a good way of doing it?
class A {
private:
int m_myInt;
public:
int myInt() const {return this->m_myInt;};
[Code] ....
I guess it works? It would lead to a lot of data shuffling in case of larger sub-components.I would really like to do the following without exposing my components so much:
B myB;
myB.a().myInt(3);
Can it be done?
The code is compiled.
If I do loops for push and pop fucntions in main.cpp the same size as Stoke everything is working properly
If loops are larger than the Stack size that goes here is a picture in the console (see screen print)
Code:
//
//(---.Array_hpp---)
//
#ifndef Array_HPP// Preprocessor gates
#define Array_HPP
#include <sstream>
#include <iostream>
#include <exception>
template <class Type>//Remove the "=double" default parameter.
[code]....
How can a member function in my derived class call the same function from its base class?
View 1 Replies View RelatedSay I have 3 classes:
class Player {
public:
virtual func1();
[code]....
Say in my main class, I have a function fight(Player p1, Player p2) and I would like to do something like this in the fight function, given that p1 is the human and p2 is the computer:
//function fight()
fight(Player p1, Player p2) {
p1.func2();
}
//using function fight()
fight(human, computer);
When I compile the program, I got this: error: ‘class Player’ has no member named 'func2()' What can I do to allow p1 to call func2 inside fight()? I'm not allowed to use pointers as the parameter for fight() and have to use the signature fight(Player p1, Player p2).
So I have a base class, lets call it base. In base I have a virtual function called update(), update just couts "base" then I have a class derived from base called derived;
it has a function called update(), update just couts "derived" then I create a vector called Vec it's initialised like this:
std::vector<base> Vec;
then I add an element into it like this
Derived DerElement;
Vec.push_back(DerElement);
then when I type:
for (int i=0; i<Vec.size(); i++) {
Vec.at(i).Update();
}
It outputs:
Derived DerElement2;
DerElement2.Update();
and it outputs this:
#include <iostream>
#include <vector>
class Base {
public:
virtual void Update() {
[Code] .....
and this is it's output:
Base
Derived
Press any key to continue . . .
I am writing a program which is using SDL library. I have two different classes which one of them is Timer Class and the other is EventHandling Class.
I need to use some member functions and variables of Timer in some Eventhandling Class member functions, Although I want to define an object of Timer in int main {} and relate it to its member function that has been used in Eventhandling member function in order that it becomes easier to handle it, I mean that I want to have for example two objects of timer and two objects of Eventhandling class for two different users.
I do not know how to relate an object of a class from int main{} to its member function which is being used in another class member function.
Lets have it as a sample code:
class Timer {
private:
int x;
public:
Timer();
get_X();
start_X();
[Code] ....
I just wondering if a base class can call the overridden function from a Derived class?
Here's an example:
//Base Class H
class BaseClass {
public:
BaseClass();
virtual ~BaseClass();
virtual void functionA();
[Code] ....
So basically, when I am creating a new object of Derived class, it will initialize BaseClass and the BaseClass will call functionA but I want it to call the function overridden by Derived class.
I know that if I call newObj->functionA it will call the overridden function. Right now I want the base class to call the overridden function "this->functionA(); in BaseClass" during its initialization. Is it possible to do that?
I'm trying to write a simple Delegate class with a Bind() and Invoke() function. For now it only needs to support a void class function with no parameters. I've searched around and found quite a few exmaples, though, those class are heavily templated and I lose track trying to simplify it.
So far my code is following:
Code:
#include <windows.h>
class Test {
public:
void DoSomething() {
MessageBox(NULL, L"Test::DoSomething!", NULL, 0);
[Code] ....
The part I am having difficulty with is assigning &Test::DoSomething to the m_Callback variable.
&tObject::DoSomething works, yet _Callback which I pass &Test::DoSomething to does not work.
Also, why does the following line work:
Code:
m_Callback = &Wrapper<tObject, &tObject::DoSomething>;
When wrapper is like:
Code:
template<class tObject, void (tObject::*Func)()>
void Wrapper(void* Object)
Should it not be Wrapper<class-typename, parameter-1>(parameter-2) // This currently creates an error
I'm writing a sorted vector implementation and trying to do it as simply as possible.
Right now, I'm declaring the sorted vector with a protected subclass of vector, then using the "using" keyword to explicitly inherit all methods that aren't related to adding new elements to the vector (so I can control the order).
Eg:
Code: template<typename T, class Cmp = std::less<T>>
class sorted_vector : protected std::vector<T>{
public:
typedef typename std::vector<T>::iterator;
using std::vector<T>::operator=;
using std::vector<T>::assign;
using std::vector<T>::get_allocator;
using std::vector<T>::at;
using std::vector<T>::operator[];
//...
};
Obviously, this is annoyingly redundant. So what I'd like to do is something using the new "delete" keyword from C++11. Is there any quick, expressive way of deleting specific methods?
Also, it's pretty annoying to have to typedef base_class::type type to inherit a type from a base class. Is there a shorter way to do that?
I've created a modeless dialog from my main dialog as follows:
Code:
m_pContainerDlg = new CDlgContainer(NULL, this);
m_pContainerDlg->Create(CDlgContainer::IDD, GetDesktopWindow());
m_pContainerDlg ->ShowWindow(SW_SHOW);
This container dialog creates a child dialog which I show inside the container
Code:
BOOL CDlgContainer::OnInitDialog(){
// Create the child dialog and show it
m_pChildDlg = new CChildDlg(this);
m_pChildDlg->Create(IDD_DIRECTORY_DIALOG, this);
return FALSE;
}
From my child dialog I then create a modal dialog when a user clicks on a button
Code:
CChildDlg:: CChildDlg (CWnd* pParent /*=NULL*/) :
m_pParent((CDlgContainer*)pParent), {
} void CChildDlg::OnBnClickedBtn() {
CMyDlg MyDlg;
INT_PTR iResult = MyDlg.DoModal(pParent);
}
My problem is that the CMyDlg is modal but to the main dialog and not to the container or the child dialog.
I am facing a real-life problem, it can be simplified as below:
#include <iostream>
using namespace std;
class B;
class A {
public:
void f1(A a) {}
void f2(B b) {}
[Code]...
There is no problem at all with the f1(), it compiles and executes without any problem. But f2() gives compilation error. How to solve this?
The error message is: error: 'b' has incomplete type This is just to define the function f2() in a class, that uses an instance of its child class as one of its arguments.
Basically, I have a base class called MainShop and it has 3 derived classes which are SwordShop, SpellBookShop and BowShop. I want the base class to be able to call a function from one of the derived classes but no matter what i do, it doesn't seem to work!
Here is my code:
#include "MainShop.h"
//BaseClass cpp
void MainShop::EnterShop(Hero& hero)
[Code]....
I have two other derived classes, but its basically the same concept. I have a function in one of the derived classes and i would like to call it from the base class. This is one my derived classes:
//SwordShop derived cpp
#include "SwordShop.h"
void SwordShop::soldierShop(Hero& hero)
{
/* some code here*/
}
I have a picture box, inside a table layout panel. The default size for the picture box is 456, 457. However, what I want to do is have the picture box be the size of the available area, even if the form is full screen.
I have the picture box dock set to fill etc. but not matter what I do, it refuses to change the dimensions from the ones above.
The only work around I could find that worked was this:
this.pbMainMap.Size = new Size(Screen.GetWorkingArea(this).Width, Screen.GetWorkingArea(this).Height);
Which is pretty useless if you are using a table layout panel. Can I grab the dimensions from the cell I am in or something?