When are you creating fields/properties for specific classes and when you are not doing it but creating them inside just lets say straightaway inside some methods within that classes. I mean if i got class where inside i want to create instance of some other class and then pass this instance to another class - should i create a field for it within class i am doing this operation or not? I was always reading that you create field/properties when its belong to class itself. So if i want only to create some instance outside class i am working and pass it to other class and this is not exactly the part of this class shouldnt i create a field for it and just create it inside method?
I am trying to run a simulation with a large number of objects (mainly arrays and vectors). I am not sure where shall I define my objects: inside or outside of the main() function, like the following two structures:
I know there is a question about scope. But besides this question (which seems have no difference between these two structures here), is there any difference in terms of execution performance or security issue?
I have startes making a game where there is 3 ships that cross the screen verticaly, and the point is to shoot them down. So far I have actually managed to do this. I have also managed to add gamescore to the ships. But here is my problem, I cant find a way to combine the score from all three ships in to one score. I have all three ships in different classes, is that wrong? When I try to combine the scores, ship score1 cant see the other scores.
Do I need to somehow have all the ships in one class. Or are there a way to read the scores from three classes, and adding them up in to one in a new class?
One of the errors I get is "the name 'score1' does not exist in the current context.
I need to have an object of class A that doesn't have a default constructor in another class, B:
Code: class A; //This is in a separate header file class B { private:A a;};
The problem is that it won't compile without a default constructor. I'm not allowed to define a default constructor, and the A object in class B has to be private so I can't initialize A a in public.
I also can't change the prototype in the interface to something like
A(int a = 0, int b = 0);
since one of the requirements is that if an object of class A is declared in main, it must not compile due to not having a default constructor. So what can I do to make class B work and compile?
Another question I have is why is this valid:
Code: class A; //#include "A.h" is in the implementation file so it compiles. class B { private:A* a;}; But not this: Code: class A;
class B { private:A a;};
This is for a project that I probably won't be able to turn in on time, but I care more about how to do this right than turning it in for full points.
Here's the problem. I want to generate an array of objects from classes.
brick[] tile = new brick[5] // originally wanted an array of 500 to play with but I thought I'd start small first
I wanted to make a draw() function in my "level01" class to generate a map (so I wouldn't have to build them in photoshop then manipulate rectangle bounding boxes). I tried several things...
First, I found a thread that worked to get rid of the null value in the array ("not set to reference of an object" error).
After that, within a for loop, I tried to initiate my values...
for (int i=0; i < tile.Length; i++) { tile[i] = new brick(); // calling the object piece[i] = new PictureBox(); // calling the object's container //tile[i].brick1X = 38; // already had a default set to it so I commented this out to see if it made // any difference... it didn't tile[i].brick1Y += 32; // if this worked, it would have drawn a 32x32 tile down the Y axis every 32 // pixels
[Code] ....
In my Form.cs, I declared my first level map as: level01 L01 = new level01();
Under the form's constructor, I instructed it to L01.draw(); so that it would initiate on the game screen.
Needless to say, I get the game screen and the frame, the menu bar I have pops up. But, no tiles.
I even went so far as to get rid of the null values for [i] in the array (using the above for loop but with fewer tasks within the loop) and created a counter that would count up += 1 every time it would make an object.
if (counter < 5) {
And would put in the above tasks inside of the logic loop. I would either get nothing drawn on the screen or it would throw an exception.
I could easily make this using XNA Game Studio in Visual Studio 2010 but I'm using VS2013 and wanted to do a program straight in C# instead of using XNA.
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Drawing; using System.Windows.Forms;
Working on a project for a c++ class and got a bit stuck.
What I am trying to do is include a class for calculating home square footage in a program I have written for my last project. When I do this, I get errors in codeblocks, on lines 74 and 87, "expected ; before 'box', and 'box' was not declared, respectively. Unsure what my snafu is... I had these two programs separate and both run without errors until I combine the two into one program.
The Light and Fan are two different vendor classes and they are not derived from any base class. I am trying to implement the Command design pattern but with generic implementation, so it should work in future with any new vendor class like Door, Window etc without much change in client code. I have thought about a Factory method but it will not work because it needs a Base class. I am trying to learn the design patterns.
Light *myobj; Fan *myobj; int choice; cout<<"Select Light (1): "; cout<<"Select Fan (2): ";
I have an array of (Student)classes created in Manager.h, which contains a new instance of class Name (name),(in Student.h)How would I go about accessing the SetFirstName method in Name.cpp if I was in a class Manager.cpp? I have tried using Students[i].name.SetFirstName("name");
// In Manager.h #include"Student.h" class Manager {
This has been bothering me for a while now, and I finally put together an example:
#include <iostream> #include <string> using namespace::std;
[Code]....
In the code above, the two classes hold pointers to each other, and that's fine but it doesn't seem right since C++ prefers to pass by reference. Yes, it can still do that (see testbox and testball) but even that seems odd to me because still you need to use pointer notation for the enclosed object. Am I the only one who feels this way, and should I just get over it? Or am I missing something that would allow an object to hold a reference?
when vpStatus is nonsense and unknown, the vaporPressure should not have a value; and if I calculate out a value for vaporPressure, the vpStatus can be set as known.
I am wondering if there is any set, pair or other structure can hold this two members together, so that when I change one's value, the other guy will also change accordingly.
Define a class for a type called CounterType. An object of this type is used to count things, so it records a count that is a non-negative whole number.
Include a mutator function that sets the counter to a count given as an argument. Include member functions to increase the count by one and to decrease the count by one. Be sure that no member function allows the value of the counter to become negative.Also, include a member function that returns the current count value and one that outputs the count. Embed your class definition in a test program and run sufficient tests to verify it all works correctly.
I get an error telling me that foo is undefined, and that declaration of function_example(int x, int y) is incompatible with the declaration of it in the header file.
I want to write encryption algorithm.first af all I need to define variable( binary input ) that it is 256 bit but I dont know what should I use...then I want to XOR this to variable ( a & b ) ( each of them is 256 bit)
In C++ there are a number of primitives that are not defined in terms of other types. By this I'm thinking
int a = 1; char b = 'M'; float c = 3.45f; short d = 0xC3A3;
Is it possible to define your own literal? What I would like to do is have a hex literal for a data type where n = sizeof(data_type). If this type were a big integer, then I would want something like:
BigInt e = 0x13CA9B0C98D983E912DA0B0A9F87E0;
My goal is to assign a value from one contingous chunk of bytes and to not do it with a string.
I just compiled some code I've been working on at a different OS/compiler and realised that Code: sizeof(unsigned long) returns 4 in one pc and 8 in another.
I've heard that bytesize conventions for basic variables were not particularly "universal" before but this is the 1st time I've had a problem with it.
how do I make a typedef that clearly indicates to whatever compiler compiler I want u32 to be an 32bits unsigned and u64 to be 64bits?
