So starting with the Item.h file :
#ifndef ITEMH
#define ITEMH
using namespace std;
class Item
[Code]...
I think I'm getting the wrong idea about strings. I thought I could add data just by using '+=' but apparently not.
I've got 2 classes, Store and Transaction and I would like to create a priority queue of objects Transaction as a variable of Store class.
My store.h
#ifndef __STORE_H_INCLUDED__
#define __STORE_H_INCLUDED__
#include <queue>
using namespace std;
#include "Transaction.h"
struct TransactionCompare;
[Code] ....
The error im getting with this set up is
error C2664: 'bool TransactionCompare::operator ()(const Transaction &,const Transaction &)
const' : cannot convert parameter 1 from 'Transaction *' to 'const Transaction &'
In this book, item 3 is about never treat arrays polymorphically. In the latter part of this item, the author talks about the result of deleting an array of derived class objects through a base class pointer is undefined. What does it mean? I have an example here,
Code:
class B
{
public:
B():_y(1){}
virtual ~B() {
cout<<"~B()"<<endl;
[Code] ....
This sample code does exactly what I want. So does the author mean the way I did is undefined?
Please consider the following code :
#include <iostream>
using namespace std;
class superclass;
class subclass1;
class subclass2;
[Code] ....
As you can see I want to create a dynamically allocated storage of references to a parent class each of which can then point to a child class, how ever I do not know how to extract the child class out again from that array so i may access its variable b.
class FlashCard {
public:
int a,b;
void PrintCard(void);
int CorrectAnswer(void);
};
void SwapFlashCard(FlashCard &a,FlashCard &b)
[Code]....
Why does Xode warn me that Type'FlashCard'does not provide a subscript operator on line 22,23,29 and 30?
I need an array of class objects but am unsure of how one might accomplish this. I have so far...
//element class driver code
Element Arsenic(lowCeiling, highCeiling);
Element Cadmium(lowCeiling, highCeiling);
Element Chromium(lowCeiling, highCeiling);
Element Copper(lowCeiling, highCeiling);
Element Lead(lowCeiling, highCeiling);
Element Nickel(lowCeiling, highCeiling);
Element Molybdenum(lowCeiling, highCeiling);
Element Mercury(lowCeiling, highCeiling);
Element Selenium(lowCeiling, highCeiling);
Element Zinc(lowCeiling, highCeiling);
Element metal[10] = {Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Molybdenum, Mercury, Selenium, Zinc};
Could the array be created in this manner or is that illegal code?
What I want to do is have an admin class which will hold all the employee objects, can add them, list and calculate salaries. I'm trying to make array of objects, not sure if it's right
here is the code
Code: #include <iostream>
#include <string>
using namespace std;
class Employee {
public:
Employee(string name, short type, int salary)
[Code] .....
class A {
Public:
A (int);
A(int,int);
int get (int,int);
};
I have written a selection sort algorithm to go sort an array of class objects by age in ascending order, the problem is that the output being given does not match what i think the code should do. when the program runs the 3 records are added to the array and when they are sorted should be outputed in ascending order, the problem is that with my code the last 2 are sorted properly but the first element does not seem to move, it remains the same as the original unsorted value.
My code for the selection sort function and the display method are below:
void selectionSort() {
int i, minIndex, minValue;
for (i = 0; i < (arrlength - 1); i++) {
minIndex = i ;
[Code].....
I have a linear search algorithm set up to search through an array of class objects it works but the output does not match, when i search for a particluar name in the array the 1st and third values int the array are found but the second value is not found..
below is my code:
int linsearch(string val) {
for (int j=0; j <= 3; j++) {
if (player[j].getLastName()==val)
return j ;
[Code] .....
So I have an array of my own class, "Restaurant," but I'm having a hard time figuring out how to store the info entered by the user into the array.
In total, I have two classes. I will show you all I have, it's a lot but I know it will be easier to understand.
My problem is in the AddRestaurant(), since that is where I should ask the user for all the information and store it in the array.
Also consider that I have to use the FTime class as well to handle the time. Basically I want to do something like this:
info[count].SetRating();
which will put the rating part of the class Restaurant into the array[count]
Also, my program doesn't compile because of the AddRestaurant and PrintAll functions since what I am showing is what I want to do, not what works.
//main.cpp
#include <iostream>
#include <iomanip>
#include <string>
#include "Restaurant.h"
#include "FTime.h"
int ReadMenuChoice();
[Code] .....
I've started programming my little program called vLibrary (program I want to make for the library in my city) and after I m done with console application I will try to implement wxWidgets.My program will be able to add new users to the system, new books and new librarians.
Now, I m confused what data types to use and how to store objects (newly created users, books etc) to my program so later on they can log in the system etc. Logic of the program is completely clear to me but I m not sure how to make array of objects and store them in memory or in a certain file, how to store password and make some kind of encryption etc.which data structure from STL should I use and how.
I'm using the SDL library and trying to match the C++11 standards... Anyway, I thought about a vector where I store all the addresses of game instances, so I can access them anytime... I tried with this function:
int instance_new(std::vector<uintptr_t> &instance_id, unsigned &instance_size, Instance *pointer) {
instance_id[instance_size] = reinterpret_cast<std::uintptr_t>(pointer);
instance_size++;
instance_id.resize(instance_size);
return 0;
}
Where "Instance" is the 'parent' class of various child classes like the player. So, if I have to search the existing of a thing in my game, I should check if the address references to an instance of class. How can I do this?
I searching for a container/collection, that can access very fast to objects with the associated id.
Arrays are a bad idea, because it can be that I must store objects with a big id for example 9394034, so the array would be to big.
Okay, I'm not entirely certain where my code is messed up, but when I run the console it asks if I want to add Employee information and then it just skips through everything when I say yes.
#include <iostream>
#include <iomanip>
#include <string>
[Code].....
Overview of problem : I am using std::vector to hold objects of Subject. Now this vector contains lots of objects( with lots I mean 10-20 objects at max) . These objects have string member values like category and sub_category. Both category and sub_category can have string which can be same of other objects's sub_category & category.
Issue: Now I want my std::vector to have only those objects whose's sub_category are unique. If category is not unique that's not a problem .
Secondly if we found 2 objects having same sub_category then we have to delete one of them from the vector. we will delete it based on some rules example
Rules for deleting are if
i) instance of Subject ->category = " Land " OR if category = "Jungle" then delete other duplicate object ,
ii) if above condition doesn't match then delete either of them.
I am wondering , how would I compare the sub-items from the vector . For example. I have class say Subject
class Subject {
public :
// some constructors,
// functions to get ., set category and sub category
std::String get_sub_category()
std::string get_category();
private:
std::string category;
std::string sub_category;
}
I have vector which stores object of Subjects. Example : vector<Subject> copy_vector;
Now what I want is to delete the object from vector that has same sub_category I am not looking for source code buT i need a starting point,? Example:
copy_vector[0] = Animal object that has sub_category Tiger
copy_vector [1] = Animal object with Lion as sub category
copy_vector[2] = Forest object with sub_category Tiger
What I want is to based on some conditions(which I can do ) remove either Forest or Animal object containing Tiger. But for that how would I do comparison? I have written the function and have checked it.
std::vector< Subject >copy_vector;
// copy_vector contains all the objects of Subject with redundant sub_category
for( std::vector< Subject >::iterator ii = copy_vector.begin() ; ii != copy_vector.end() ; ++ii ) {
sub_category = ii->get_sub_category();
[code] ....
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 .
I have been working on an assignment where I have to add three objects of a class Matrix. The class should have the flexibility to add more than two oprands without changing any operand on Left hand side of the '=' operator.
Matrix obj1, obj2, obj3, obj4
Obj1=obj2+obj3+obj4
I am using the following code for this
Matrix Matrix::operator + (Matrix &obj) {
if((this->Columns == obj.Columns) && (this->Rows == obj.Rows)) {
for(int i=0;i<obj.Rows;i++)
[Code] .....
the problem is that it is just adding only 2 operands. How can I add more?
So I'm trying to store class objects in a vector:
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
[Code]....
1. Am I storing it correctly?
2. How would I access the stored data, say, if I wanted to compare it to other stored data or COUT it?
For a beginners C++ lab, I have a base class Employee and two derived classes HourlyEmployee and SalaryEmployee. In main, I have a vector defined as vector <Employee *> VEmp; It's then passed to a function to get the input, which works fine. But what I'm struggling with is another function with the header "printList(const vector <Employee *> & Ve)". It's supposed to loop through the vector and call the appropriate printPay function, which is a seperate print function inside each derived class. How do I loop through the vector and print it out? I was trying to do a for loop and something like "Ve[i].printPay();", but that doesn't work. So how would I do it?
Here's some snippets of the relevant code.
class Employee {
....
virtual void printPay() = 0;
};
class HourlyEmployee : public Employee {
[Code] ....
For example when I have:
Class A{
B objectB;
};
Now when I instantiate the object of class A like:
main(){
A objectA;//option 1
A* pObjectA = new A();// option2
}
How is objectB stored in memory (stack heap etc.) for both options??
i ran the following code in the latest version of code::blocks and it tells me that the objects cout and cin are not declared in this scope. what is the problem?
I used to use Turbo C++ 3.0 and i had no problem whatsoever with that compiler. But now i am trying to move to code::blocks but it is proving very very hard as all the standards have been changed.
I am a school student and thus, we had been told to practice on Turbo C++ 3.0 and now i am unable to unlearn it. Also, if i use printf in place of cout there is no error but i want to use cout as it is what i am comfortable working with.
#include<fstream>
#include<conio.h>
int main() {
using namespace std;
char name[20];
[Code] ....
Is there some document to which i can refer so as to get the latest C++ standards which is C++0x i believe?
Is dere is any limit in number of objects of a class?
View 16 Replies View RelatedI am working on a project that requires me to create objects from a abstract class that has 2 child classes (that need to be derived). Any examples on how to do this? I looked online and the examples were pretty vague. the main error that I am getting is when I make a temp object with & in front of it (such as Employee &genericEmp) it throws a must be initialized error.
View 6 Replies View RelatedRunning into a snag in my program. I can't seem to figure out how to have an object of a class be able to look at all the other objects of its own class.
Reasoning being, I'm working on a game with multiple ships flying around in the same space. Each ship is a class.
Each ship has an x and a y, and needs to compare the angle and distance of other ships' x and y coordinates to see if they're visible on the same screen.
How to tell an object to look at objects of its own class.
Here's some code:
common.h
#ifndef COMMON_H_INCLUDED
#define COMMON_H_INCLUDED
int dist(int x1, int y1, int x2, int y2);
int get_info(int which);
[Code] ....
Basically, I just don't know how to properly write a function, call, or how to get the info I need, to the Player::get_closest() function so that it can see the other play objects.
regarding dynamic vector.
Shape2DLink.cpp
void Shape2DLink::InputSensor()
{
string shape,type;
[Code]....
So i'm actually using polyphormism for calculating the area of the cross and other shapes. so how do I actually make use of dynamically create an object this way?
do I create them in my Shape2DLink or in my individual child classes?