I've created an Array of pointers to objects using:
Person ** A = new person * [arraysize];
When I intend to access a specific person do I have to do this? :
something = A->[i];
and when I want a specific object within my struct do I have to do this? :
something_else = A->[i]->random_int;
my code:
int OKCount=0;
int WaitingCount=0;
int ReservationCount=0;
Flight::Flight(int capacity, int waitingMax) {
seats=capacity;
[code].....
reservations is a data member in the class flight as:
Reservation **reservations;
OKReservation is a derived class and its abstract base class is Reservation.
My problem is that the reservations array loses its value in other function
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.
I am using OpenCV to read and manipulate a set of images, which I need to store in an array to work with them. Here is a snippet of the code:
#define MAX_IMAGES 8
typedef Mat* MatPtr;
int main(int argc, char** argv) {
char imageName[] = "./res/imageX.tiff";
MatPtr datacube[MAX_IMAGES];
[code].....
I have an array of pointers to Mat objects (an OpenCV class used to hold info and data about an image), which I will use to store the images. The function imread reads an image and returns a Mat object loaded with the relevant data about the image.However, this gives me a nice segfault when the assignment takes place. Of course, I can swap it with the following code, but since I'm working with big images (2048x2048 and upwards), it's really inefficient:
for(unsigned int i = 0; i < MAX_IMAGES; i++) {
imageName[11] = 49 + i;
datacube[i] = new Mat(imread(imageName, -1));
}
Is there any way to do this elegantly and without much hassle?Again, excuse my rustiness and anything completely stupid I might have said. It's been a long time since I worked with C++. Managed to circumvent the problem by using a STD vector instead of an array. I'd still like to know the answer to this riddle...
I have a data structure defined up here called this:
typedef list <classSpec*> ClassSpecList;
I'm trying to add stuff into the list here based on functions that return certain values of that match the same data type. In one function, I have a list pointer object defined here and I have another statement that calls a function.
ClassSpecList *answer = 0;
classSpec *thisanswer = parseClass(br);
Basically I'm trying to add the results of what thisanswer returns into my main ClassSpecList. Problem is, when I try
answer->push_back(new classSpec (*thisanswer));
It compiles but I get a seg fault
When I try somethign else like:
answer->insert(ClassSpecList.begin(), *thisanswer);
I keep getting primary expression errors and I do not know why. I even tried it with other list made without typedef and I still get those.
Im creating a program for a race. The Race class has a vector of results and each element of that vector is a pointer to a result. The Result class has a Time and a pointer to a Participant. So in each race there are various results and it is a result for each participant.The Time is a class that has hours, minutes and seconds. How can I sort the vector of results from the result of the participant with the fastest time to the result of the participant with the slowest time?My code is like this:
//.h file:
class Time {
unsigned int hours;
unsigned int minutes;
unsigned int seconds;
[code]....
What am I missing to get my code to work?
Im creating a program for a race. The Race class has a vector of results and each element of that vector is a pointer to a result. The Result class has a Time and a pointer to a Participant. So in each race there are various results and it is a result for each participant. The Time is a class that has hours, minutes and seconds. How can I sort the vector of results from the result of the participant with the fastest time to the result of the participant with the slowest time?
Im getting some errors in my code. I put the error as comments in the code. Each error is after the line where it occurs. My code is like this:
//.h file:
class Time
{
unsigned int hours;
[Code]....
I'm trying to create an array of pointers to pointers which will point to array of pointers (to strings) I tried
Code:
int i;
char *string[]={
"my name is dave",
"we like to dance together",
"sunny day",
"hello",
[code]...
the app keeps crashing , I don't know how to make the array-elements to point to another array-elements..
So I'm trying to fill a vector with pointers to account objects.
std::vector<account*> fill_vector() {
std::vector<account*> temp;
std::ifstream s;
std::string str;
s.open("H://account2.dat");
[Code] ....
The accounts have four different types and I am supposed to skip over ones that have an invalid account type and throw an exception:
account* factory(std::string account_code, std::string first_name,
std::string last_name, char type, double balance) {
try {
if(type == 'A') {
simple_account *a = new simple_account(account_code, first_name, last_name, balance);
[Code] .....
My problem is they program will not skip over my rejected accounts.. still adds them to the vector but I cant figure out why!
Using SFML, I had a Board class which held multiple vectors of all of my object types in the game, and then it also held a vector of pointers to the memory addresses of these object instances, like this
class Board{
//...
std::vector<AbstractObject*> GetAllLevelObjects(){ return allLevelObjects; }
//so these are used to hold my object instances for each level
[Code]....
When looping through this vector and drawing the sprites of the objects, I get the runtime error 0xC0000005: Access violation reading location 0x00277000. I solved this error by storing the vector of pointers in the class that holds my Board instance, but I'm wondering why only this solution worked? Why couldn't I just have my vector of pointers in the same class that the instances of those objects were in?
Code:
void Class1::Func(shared_ptr<type1> parameter)
{
}
or
void Class1::Func(const shared_ptr<type1>& parameter)
{
}
or
Should I ever pass arguments/parameters to other objects using shared_ptr's or raw pointers?
I have a class called Question:
#include <string>
#include <vector>
using namespace std;
class Question {
string title;
vector<Thing*> posAns;
vector<Thing*> negAns;
[Code] ....
error: no instance of overloaded function 'std::vector::push_back()' matches the arguments list
argument types are (const Thing *)
object type is: std:: vector<Thing *, std::allocator<Thing *>>
So it cannot be constant, what if I just leave it non-constant? Will it be safe?
I'm trying extremely hard to understand pointers and I have the basic concept down.. I feel as though my knowledge of dynamically allocated pointers and pointers in general is not enough to understand the logic behind what I'm trying to do. The problem is that the donations array must be able to accept any number of donations. I've made it do just that, but there is also an array of pointers which must each point to the same element in the donations array. The program works if I assign int *arrPtr[100] for example, but it does not work if I try to dynamically allocate it to accept the same number of elements for donations entered by the user. Here it's the snippet
#include <iostream>
using namespace std;
//Function Prototypes
[Code]....
I am trying to initialize an array of pointers to an array of characters, I can do it in 3 lines but I really want to do it in one line at the same time keeping the #define.
3 lines initialization (can compile)
======================
#define A 1
#define B 2
char row1[] = {A|B, B, A};
char row2[] = {B, A};
char *test[]= {row1, row2};
1 line initialization (failed)
===============================
char *test[] = { {A|B, B, A}, {B, A} }; // <- how do i do this??
I do not want this because it waste ROM space
=============================================
char test[][3] = { {A|B, B, A}, {B, A} };
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?
When I make an array of new objects and write delite arraySelector, will that delite all of the array elements or just the first one?
View 9 Replies View RelatedI have Class A as a base class , and Class B , C derived classes from A and there's class D who have a data member (pointer to Array) of type A (Composition)
class D{
A **a;
int size;
.......
a = new A*[size];
......
};
And i have Print method , in its body i have to specific element (if it from class B or C ) with a given ID(both B and C have a data member ID ) there should be 2 options in print function .. printing elements for class B , or printing elements for class C ? how can i specific the elements ?
I have a homework requiring me to use quicksort on a pointer array of CDs. They are sorted by the title. I have tried the general solution for integer arrays which sets the pivot at the middle integer but it didn't work/ stopped working when I tried to start sorting the already inputed CDs. The same is happening with the current version (an adaptation of pieces of code):
void swap(CD &a, CD &B)/>
{
CD temp;
temp = a;
[Code]....
Define a PayRoll class that has data members for an employee's hourly pay rate (an integer , representing cents) and number of hours worked (also an integer ). The class provides two member functions, setRate and setHours that assign the value of their parameter to the appropriate data member. The class provides a third member function, getPay, that returns weekly gross pay (in cents), computed as follows: hours times rate for the first 35 hours plus hours times rate times one and a half for any hours past 35.
View 3 Replies View Relatedi want to save similar objects, meaning having same superclass, in an array. Example: I have a superclass vehicle. Class car and truck inherit from vehicle. Now i have a few from both of them an want to put them in an array, vector, set or else. Is this possible in C++ or are there an workarounds? When i remember right, Java and C# offer this feature.
Here again an example:
Code:
class vehicle{
int mMaxSpeed;
} class truck : public vehicle {
int mTrailerLength;
} class car : public vehicle {
[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] .....
I am working on building a graph of a maze problem using an adjacency list and my own custom class Node.
Each Node has a vNum and jumpAmount integer variable, the vNum is the unique key.
If I have an array of lists of Node objects declared by: Code: forward_list<Node> adjacencyList[10] I skip the 0 row and only use 1-9. It makes more sense logically for my program and Im not worried about wasted memory at this point.
How could I go about traversing and outputting member variables for all the Nodes in each list in my array?
Say my code builds the following adjacency list:
Code:
1 -> { 2, 3, 4, 7 }
2 -> { 1, 3, 5 }
3 -> { 1, 2, 6 }
4 -> { 1, 5, 6, 7 }
5 -> { 2, 4, 8 }
6 -> { 3, 4 }
7 -> { 1, 4, 8 }
8 -> { 5, 7, 9}
9 -> { 8 }
where the values in brackets are the nodes that have an edge with the ith row node. Had to put it in code tags for the thread to be allowed to post.
I am using the forward_list library for my list functions and this is where my problem arises. The cplusplus.com - The C++ Resources Network website iterates through the list using:
Code:
for ( auto it = mylist.begin(); it != mylist.end(); ++it )
std::cout << ' ' << *it;
Obviously this works for ints, doubles, etc, but not objects with member variables. My attempt to replicate this code for my problem looks like:
Code:
for( int i = 1; i < 10; ++i ) {
cout << "Node " << i << " -> { ";
for( Vertex it = adjList[i].begin(); it != adjList[i].end(); ++it )
{
cout << it.getVNum() << ", ";
}}
I have to come up with user defined conversions for this to work and I have never done such a thing. Is there a way to go about doing this to avoid user defined conversions, because if there isnt I feel like attempting to do this specific problem might be a little too difficult for someone who hasnt defined any custom conversions.
Potentially, I could write my own List class and have a next pointer member variable that points to the next object in the list and use that to use a dot reference to a get function to display member variables. This is how I learned linked lists back in my Data Structures class. However I am trying to avoid that for the time being, as that would be a lot more code to implement rather than just figuring out how to use the forward_list library.
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.
class A {
Public:
A (int);
A(int,int);
int get (int,int);
};
Im supposed to create an to array of eight Circle objects initialized with the following radii: 2.5, 4.0, 1.0, 3.0, 6.0, 5.5, 3.5, 2.0. Then use a bubble sort to arrange the objects in ascending order of radius size before displaying the area of each object.
The error I get is "Cannot open include file: 'Circle.h': No such file or directory". Do I have to create a separate file for it?
#include <iostream>
#include <iomanip>
#include "Circle.h"
using namespace std;
class Circle {
public:
Circle()
[Code] ...