class Date
Date(int=1, int=1, int=1990);
class Person
Person(string="", string="", Date=NULL);
class RealEstateAgent:Public Person
RealEstateAgent(string="",string="",Date=NULL,Date=NULL,int=NULL, double=0.0);
}
[code]....
how can I assign default values with Customer object and RealEstateAgent?
I was making a template list class, and using it to make list of objects of my own class.It works fine with integers, but not with other classses.
template <typename T>
class CList {
public:
struct Node {
T data;
Node* next;
[code]....
While in AddElement(), it gives error - Default constructor not available.
template<typename T>
bool CList<T>::AddElement(T t) {
bool result = true;
if (head == NULL) {
[code]....
what is wrong here.
Let's say I have a Car object , and it contains inner Engine object.
Code:
struct Car{
Engine mEngine;
};
In order to initialize the engine object NOT by the default constructor (if it has any) , we use initialization semantics:
Code:
Car::Car:
mEngin(arg1,arg2,...)
{
other stuff here
}
Now it gets tricky: Let's say a Car objects has 10 inner objects, each object has about 5 variables in it . Car is a base class for , e.g. , Toyota class. you don't want the Car class to have a constructor with 50 arguments. Can the inner objects of Car be initialized from the base class , e.g. Toyota?
Code:
class Toyota:
Car(...),
mEngine(...),
mGear(..)
{
...
};
The other options are:
1) like said , create a Car constructor which gets 50 arguments, then initialize Car as whole from Toyota - the code becomes less readable and less intuitive
2) Car constructor which get built-objects as arguments and initialize the inner objects with copy constructor . the code gets more readable but then you create many excess objects .
Basically, I need to set a variable outside of the constructor and make it accessible to the entire class.
It would need to work something like this:
#include <iostream>
#include <string>
template <typename MT> class CallbackFunction
{
[Code].....
class A {
Public:
A (int);
A(int,int);
int get (int,int);
};
can we make a class without any data member ? but it may have member functions ! in c++
View 2 Replies View Relatedis this possible to make a class without any data member in c++ ?
View 1 Replies View RelatedThe question says that:
#include<fstream.h>
#include<conio.h>
#include<stdio.h>
#include<string.h>
[Code].....
But then the 2nd part of the question itself says that "Acno entered by the user". So we need to identify/search for an account with that Account Number. How can we do this without comparing Acno with S.Acno? I know that S.Acno is not accesible as it is a private member but then how to compare Acno without even using a member function(public) that can return the value of Acno?
First I wrote a Binary-tree class to draw a binary tree on the window. The nodes were small circles. Then I become wanted to change the shape of the nodes from circles to triangles by another class, Binary-tree-derived which is derived from Binary-tree class. I wrote the below code to do the job but I get two errors about constructors. First, code:
/* The binary-tree class, one of the topics that has been said in Programming Principles and Practice using C++ book by Biarne Stroustrup.
This code is written by R Abbasi (s.rabbasi@yahoo.com) */
#include <Simple_window.h>
[Code].....
Errors are:
Error12error C2512: 'Binary_tree' : no appropriate default constructor availablec:userscsdocumentsvisual studio 2012projects est_1 est_1 est_1.cpp91
13IntelliSense: no default constructor exists for class "Binary_tree"c:UsersCSDocumentsVisual Studio 2012Projects est_1 est_1 est_1.cpp91
How do you write a default constructor?I need to use a default constructor that will initialize the data members:
- salesPerson to “Unknown”
- noOfWeek to 13
- amount to point to an array of thirteen 0.00s.
This is my weeklysales class
class WeeklySales {
char* salesPerson;
double* amount; // Pointer to an array
int noOfWeek; // Size of the array
};
Here's my attempted code:
//default constructor
WeeklySales (){
salesPerson="Unknown";
noOfWeek = 13;
amount = 0.00;
}
A compiler auto created default constructor is called a synthesized default constructor. It will initialize the built-in members to 0 or not depends on where the class object is defined? if I define a class
class point{
public:
double x, y;
};
if I define point point1; in global scope then point1.x and point1.y will be initialized to 0, if I define point point2; in a local scope, then its x and y won't be initialized? If it is like this, then I believe if there are built-in type members in a class, then the synthesized default constructor is almost useless!
I have a question about the default constructor.
To my best understanding, the compiler will provide me with a deafult constructor only if there are no any user defined constructors, at all. Now consider the following code:
Code: class MyClass
{
private:
int m_data;
public:
MyClass(int init):m_data(init){cout<<"Ctr called"<<endl;}
[Code] ....
How is it that suddenly, there is a default constructor?
trying to practice the object-oriented part of it by converting my java programs into c++. I believe I understand the concepts of a header file and declaring the functions in the .cpp files. I keep getting this "Undefined reference to NamedStorm::NamedStorm()" error.
NamedStorm.h
#ifndef NAMEDSTORM_H
#define NAMEDSTORM_H
#include <string>
#include <iostream>
// NEVER use using namespce in header, use std instead.
using std::string;
[code]....
Im trying to create two box in this program using the default constructor. When i call to try and display the info, it says that x, y, and z are not declared in this scope. i wanted to have the user cin the length, height, and width using the void setBox function.
#include<iostream>
#include<string>
#include<cstdlib>
using namespace std;
class Box{
public:
[code]....
In C++ if no user defined constructor is provided for a class the compiler automatically provides a implicit default constructor.
An implicit default constructor is equivalent to a default constructor with no parameters and no body ?
So what is the use of a implicit default constructor provided by the compiler, if it is not going to do anything ?
i tried running my code and i keep getting the error "call to implicitly-deleted default constructor of 'node'. My code is as follows
//.h file
typedef struct node * point
struct node{
string data;
node *next
}
[code]....
I get the error at the line "ptr1 = new node;" I tried putting a default constructor for my node struct and that fixed the problem but a new problem arises. It states that i have a linker error after i compile it with a default constructor.
For my default constructor I need to set an array of strings to null and the size variable to 0. Here is my code for that
DynamicStringArray::DynamicStringArray() {
*DynamicArray[]=NULL;
size=0;
}
When I try and compile it I get an "expected primary expression before ']' token" error.
Is this example correct? This example from a book
Constructor of the Base Class
Person::Person(char* n="", char* nat="U.S.A", int s=1)
{
name = n;
nationality = nat;
sex = s;
}
Constructor of the Derived Class (inherited from the base class)
Student(char* n, int s=0, char* i=""):
Person(n, s)
Why the initialized list of the base class constructor doesn't match the initialized list of the derived class constructor? I know this book is a little bit old, I'm not sure if this wrong in VC++ 2010?
I notice I keep making the same mistake of not declaring certain objects, variables or lists inside the constructor so they e.g. a list populates when the view loads.
Which makes me think about it this way. Why do I need the constructor and when do I declare objects inside the constructor?
Maybe it just comes down to me not understanding the fundamentals of how to utilize the constructor.
What the best way to initialize a constructor in an array of objects?
Usually I declare an array of objects like so:
Code:
Car toyota[100];
Is this the only way I know to initialize a constructor of an array:
Code:
for (int i = 0; i < 100; i++)
{
toyota[i] = Car(x, y);
}
Is this the proper way?
to initialize this object? Why C++ FAQ says no? Here is my code,
Code:
class A
{
public:
A(int x, char c);
A(int x);
[code] ....
I don't have any trouble to call the constructor A(int x, char c) from another constructor A(int x).
I have little problem which causing memory leaks.
Parent > Multiple Child(Parent parent) > Child destructor deleting parent => next Child destructor crash
Example code: without using:
class Parent {
public:
Parent() {
for(int i = 0; i < x; ++i) {
for(int j = 0; j < y; ++j)
childs[i][j] = new Child(this);
[Code] ....
If you read code, on Parent destructor i = 0 & j = 1 its going crash.
Parent will be deleted aswell, but it give me assert: _block_type_is_valid(phead- nblockuse)
I have a class that defines a window (a popup dialog of sorts), and I want the name of that window to be constant. The only problem is that the name of the popup needs to match the title of the parent window, and I get the name of the parent in the constructor. So how do I go about defining this member variable to be constant and initializing it with a value in the constructor?
I want to do something like this, but I know this isn't allowed:
/* class.h */
class foo {
public:
foo(*parentWindowPtr);
[Code] .....
I should mention that yes the name of the parent window is const char *, and I would like to keep it this way.
I have a small class and a vector to hold the objects.
Code:
class result_holder {
public:
// initialize class members
[Code]....
The purpose is to keep results and be able to sort the results on row_value while keeping the id and name values in registration with the row_value. I am running allot of tests and keeping the top n results. The idea is to sort the vector so that I can just examine the object in the last element to see if it should be replaced by a better result.
I know that this kind of thing is often done with an overloaded operator or a functor, but I am a bit out of my depth with that, especially determining what class variable will be used for the sort. sorting the above objects on the row_value variable?
refer to the code below, the attribute class is created with the value type and default value, but why it doesn't work for std::string?
#include <string>
#include <iostream>
using namespace std;
[Code].....
The reason that class members are private by default is because, in general, an object of a class should be a self-contained entity such that the data that make the object what it is should be encapsulated and only changed under controlled circumstances. Public data members should be very much the exception. As you’ll see a little later in the chapter, though, it’s also possible to place other restrictions on the accessibility of members of a class.
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