I am new to C++. I am trying to create 5 instance object of class Test. I wonder if these two codes are the same.
Test testArray[5];
//which one is the correct way or what is the correct way?
for(i=0;i<5;i++)
{
Test testArray;
}
I'm new in object oriented programming. I need creating a global object/instance of a class, that can be used by any function.
View 19 Replies View RelatedLet's say I reference a dll in my project that has an abstract class in it:
public abstract class Module {
public string type;
public abstract string doSomething();
}
And then I have an Assembly object, loaded from a dll that is not referenced in project, but rather loaded during run-time, containing:
public class Tester : Module
{
public static string type = "Test";
public override void doSomething() {
//Stuff being done
return "hello";
}
}
How can I get the value of "type" in the class that is loaded during runtime? How do I use the "doSomething" method of it and get the returned object?
I'm trying to learn as much C++ as I can. I was writing a program that mixes linked lists and classes. There is the class "Obj" which only holds an integer called 'data' and the classic "struct node" structure for linked list, but this time the "node" structure will hold an instance of "Obj" Class and the next* pointer.
#include <iostream>
using namespace std;
class Obj {
private:
int data;
public:
[code]....
I am creating a program that allows a user to create multiple 'sequences' and multiple 'filters' and then apply a filter to a sequence.
Each sequence and filter is an array of values.
How do I go about allowing the user to create a 'new' sequence and then store the location so I can access it again later? Once they have created a new sequence they can go on to create another sequence and ten maybe a filter and then another sequence etc etc .. and then they can select sequence 1 and edit the values if they so wish.
They would be asked how many sample values for the sequence, and then I would create a sequence with that many values and an id (1,2,3,4...). They could then enter this id to view/edit the sequence.
The entering/editing values part I am fine with. I just don't know how to allow them to create multiple new instances of a class without using an array so something like..
sequenceClassName somearray[10];
int i;
*create a new array*
somearray[i].create_class(how_many_samples)
i++ //so next sequence they create is 2,3,4.. etc
- this then calls the member function that creates an array using 'sample_values = new float[how_many_samples]' and the user can input their data and edit it whenever by entering the id which will correspond to the somearray[i].
However that approach only allows them to enter a maximum of 11 sequences. It all depends on how big I make that initial array and it just seems like the wrong way to do it.
( how to interact with them, just how to create multiple classes and recall them later to access the data!)
I have a non form class. I want to update label/ check status of check box etc.. in non form class ( here resides functions that contains logic). How can i do that ?
View 4 Replies View RelatedI have a method to take a Tile object and make an instances of it based on some data from the original object. Than it is suppose to manipulate the a specific instance and save the results. The first loop through it works but it changes all instance as well as the base.
public static int recurse(int count, Tile[,] b,Huristic h,int check) {
if (check==1) {
boardState.Add(B)/>;
return check;
} if (check == 0)
[Code] .....
My thought is that I would need to establish a variable for the class in the header and call the class within the .cpp file
//class A.h
B b;
Then in class A, to create the object and use a method from the object I would -
//class A.cpp
A::A(){
b();
}
int someAmethod(){
b.bmethod();
}
I am trying to use web api in order to return custom json response keys. For this i have return a custom class to return json response
Custom Class:
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
[Code].....
I have a combobox with Items 1024
2048
4096
8192
String cach = form.comboCache.SelectedItem.ToString();
I am using the above code to retrive an item selected by user,But this line is giving an exception "Null Reference Exception, Object reference not set to an instance of an object"
I wanted to create a new class object and I want to name it from a string. Something like this:
string name = "Mike";
Customers name;
//to create a new object in customer class using the name string
Is there any way to do this?
I am using session to pass object from controller to custom class in MVC Web API. here is my code, i am getting error at session.
public HttpResponseMessage Get()
{
var person = db.Persons.ToList();
[Code]....
Code:
public class ColorGenetics
{
public static hk1Class jw;
public static linkedClass link;
}
[code]...
Code builds fine but compiler says I tried to use bject link w/o providing an instance. Class linkedClass has an instance of Class hk1Class set to var jw1.I had linkedClass useing the same var jw for the object instance. I changed it to jw1 thinking that would clear it up and it didn't.
I need to send same instance of object of a class in two function (Main function and thread function). The class is something like this:
//The class need to have constructor.
Class ABC {
public:
DWORD *IdG;
ABC(int number) {
IdG = new DWORD[number];
}
}obj(32);
The obj(32) is called in following two function. Function F1 is called using thread in main function.
void F1() {
obj.test;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) {
obj.test1;
_beginthread(F1,0,(void*)number);
}
The code works well when the object of class ABC is created as shown above. My problem is the value that is passed in the object ('32') is to be read from the file.
If I read the file and create object separately in Main function and function 'F1' then , function 'F1' is not executed.
How to create same instance of object for Main function and function 'F1' with value passed in the object taken from the file.
If I have a class object and multiple vectors, how do I make sure I store the same instance of that object in both vectors? For instance:
Object object;
std::vector<Object> vectorOne;
std::vector<Object> vectorTwo;
vectorOne.push_back(object);
vectorTwo.push_back(object);
Are the objects in both vectors the same instance of the object? Like if I called vectorOne[0].setValue(somethingDifferent); would the value be changed for the object in both vectorOne and vectorTwo? If not, how do I make sure that I only have one instance of the object I'm trying to store in multiple vectors?
I'm trying to make a "Rain" application, by drawing some lines on the form, and then they must fall. So here is my start code:
public partial class Form1 : Form {
public Form1() {
InitializeComponent();
}
Random r = new Random();
Graphics paper;
Line line;
[Code] ....
So when I start debugging I get the "Object reference not set to an instance of an object." error. If I remove the comments lines at "timer1_Tick" this error doesn't appear of course. What can I do to escape from this because it follows me everywhere I go />. I tried to make with arrays, but same problem.
I have this class:
class Excuse
{...
public string Description { get; set; }
public string Results { get; set; }
public DateTime LastUsed { get; set; }
public string ExcusePath { get; set; }
....}
[Code] ...
When I run it, I do get the messagebox popping up with the correct description, but then nothing happens. When I debug, I see the fields under the UpdateForm() method are set to null.
I'm guessing this happening because it is looking at the 'currentExcuse' that was declared in the form body. I thought however that redeclaring 'currentExcuse' in the method would overwrite this instance or am I wrong?
Do I need an array to make this work?
I have an MFC application(.exe) in which i am creating an pointer object to CComQIptr<chemst::IChems>myinfo and after this i have using cocreate instance i had created the object launching that object, so Where i am using that CComQIptr object.
I have been creating instance to that COM exe (child exe) and at the end of the function i am releasing that object (myinfo->release).i want to create single instance for it and i want to use them in different .cpp files and finally i want to kill the child exe. Even though i release the object it is still alive.(Visualising in Task manager whether the exe is still alive or not).
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.
There are two ways to access the members of class A inside class B:
1) Making an instance of class A in class B
2) Deriving class B from class A
So what is the basic difference in both ways as we can do same kind of work with both ways?
I'm currently learning the Qt framework and doing my first tutorial. Straight away I saw something that baffled me:
notepad.h
Code: namespace Ui {
class Notepad;
}
class Notepad : public QMainWindow
[Code] ....
Note the ui pointer and the heap allocation in the class constructor; I can't wrap my head around why one would do this. What's going on here?
I am putting a instance o the Vehicle Class inside the constructor of the Calculate Class then calling it later. I get a warning saying the variable is not used and a error when I try to used the functions from the vehicle class saying use of undeclared identifier.
Code:
#include <iostream>
#include "Calculate.h"
#include "Vehicle.h"
#include <fstream>
Calculate::Calculate(){
[Code] ....
Okay so I have a class Student, which takes a number and a vector as a parameter for the constructor. Everything works well, until I output the values of the vector for every instance. The problem is that the same vector is being shared with EVERY instance I create, but I want it to be unique for every single one!
//Student.h
#ifndef __Grade_calculator__Student__
#define __Grade_calculator__Student__
#include <iostream>
[Code].....
I was wondering if (in C++) you can instantiate a class (class foo) then have said class return the already instantiated object. (foo::instance())
In other words, can I have a class return it's-self via it's own methods? I want to be able to create a class (i.e. class foo) early in my program so it is already setup and ready to go. Then, farther down the line, I want to be able to call functions from that class without having to pass that object as an argument to my calling function. Can I do something like so:
MyClass::ReturnSelf()->foo();
or
MyClass::ReturnSelf().foo();
I have a background in c# and am very frustrated with c++. If I created a class in c# like so:
public class Memory{
int x = 0;
int y = 0;
int height = 0;
int width = 0;
string firstname = "Bob";
string lastame = "Chester";
}
and then created a new instance of this class from a separate class by doing:
public class Main{
Memory mem = new Memory();
}
I have raked the internet for a way to create a new instance of a class in c++ while keeping its default values and have come up empty handed.
The case is like
class B{
public:
somedata;
somefunction();
}
class A{
public:
data;
function();
}
in somefunction i want a pointer to current object of class A m new to c++