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• Trouble Copying custom class initialization

  - by Parad0x13

  I have a custom class of type NSObject that contains a single NSMutableArray. This class is called Mutable2DArray and is designed to emulate a 2 dimensional array of type NSMutableArray. There is a custom init method - (id)initWithX:(int)x Y:(int)y that asks for the dimensions for the array and allocates the required arrays within the only array the class owns. My issue is when I try to copy an instance of Mutable2DArray I get an error saying the copyWithZone is an unrecognized selector. I thought copy was a base method of NSObject so I'm confused why I cant create a copy of the instance like this: Mutable2DArray *Array1 = [[Mutable2DArray alloc] initWithX:10 Y:10]; Mutable2DArray *Array2 = [Array1 copy]; Am I missing something so obvious here?

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• Confused about Base class libary and Framework Class Library

  - by n0vic3c0d3r

  Is ADO.NET and ASP.NET a part of Base Class Library? The information given in wikipedia looks ambiguous to me. In the figure, it is shown as a separate block. What is the difference between Base Class Library(BCL) and Framework Class Library(FCL)? Is FCL as a part of .NET Framework? If so why is FCL not shown in the figure as part of .NET framework? Got confused!!

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• Using control from a separate class in C#

  - by DazSlayer

  I have a program that dynamically creates controls when it starts, it works just fine when the code to do this is in the class of the actual form. I tried moving the code to a separate class and found that I could not use Controls.Add(). How can I add controls to the Form from a separate class? This is what I have so far: TextBox txtbx = new TextBox(); txtbx.Text = "asd" + x.ToString(); txtbx.Name = "txtbx" + x.ToString(); txtbx.Location = new Point(10, (20 * x)); txtbx.Height = 20; txtbx.Width = 50; Controls.Add(txtbx); Error 1 The name 'Controls' does not exist in the current context

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• C# cross class enum visibility - Possible?

  - by 537mfb

  so i have a class ClassA that contains an enum MyEnum, and a class ClassB that references that class (different Projects) and so in ClassB i have a using ClassA; clause and i can access that enum using something like MyEnum value = MyEnum.EnumValue; Now on a third project i have my Windows form and it has a clause like using ClassB; Now what can i add in ClassB to acess that enum on my windows Form? Is it even Possible? i would like to avoid having to add ClassA to my form just to access an enum. The idea is that ClassB is sort of a manager between my form and the functionality in ClassA - but i would like to get access to that enum as it makes a lot of tasks easier

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• Unable to Cast from Parent Class to Child Class

  - by Paul

  I am trying to cast from a parent class to a child class but I get an InvalidCastException. The child class only has one property of type int. Does anyone know what I need to do?

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• Defining private static class member

  - by mnn

  class B { /* ... */ }; class A { public: A() { obj = NULL; } private: static B* obj; }; However this produces huge mass of linker errors that symbol obj is unresolved. What's the "correct" way to have such private static class member without these linker errors? Edit: I tried this: B *A::obj = NULL; but I got about same amount of linker errors however this time about already defining A::obj. (LNK2005). Also I get LNK4006 warnings, also about A::obj

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• I have$('.class:first'), I want $(.class:fourth') using jquery

  - by Jean

  Hello, I can select the first item in the div using $('.class:first') Now since I will have random id values, and the class remains the same, I want to access the id of the fourth element, will it be something like this $('.class:fourth') using jQuery. Thanks Jean

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• Static member object of a class in the same class

  - by Luv

  Suppose we have a class as class Egg { static Egg e; int i; Egg(int ii):i(ii) {} Egg(const Egg &); //Prevents copy-constructor to be called public: static Egg* instance() {return &e} }; Egg Egg::e(47); This code guarantees that we cannot create any object, but could use only the static object. But how could we declare static object of the same class in the class. And also one thing more since e is a static object, and static objects can call only static member functions, so how could the constructor been called here for static object e, also its constructors are private.

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• Difference between var and Class class in object creation

  - by Divine

  Its a silly question, however shocked to see different behaviors. Learning a lot. Lets say I have two classes below Class A { public void Display() { } } Class B : A { public void Display() { } } Class C : B { public void Display() { } } Class Final { static void Main() { var c = new C(); // B c = new C(); //My doubt is, both of the above gives different results. May I know B c = new C() creates object of B or C? What I understood is, it creates object of B. Then why we say "new C()"? I agree with C c = new C(); But I thought, B b = new C(); creates object of B. Where we use this style? Only when utilizing runtime polymorphism? (Overriding methods)? } }

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• Problem with default member functions of class in C++ (constructor, destructor, operator=, copy cons

  - by Narek

  We know that compiler generates some member functions for user-defined class if that member functions are not defined but used, isn't it. So I have this kind of code: class AA { }; void main() { AA a; AA b(a); a = b; } This code works fine. I mean no compiler error. But the following code.... class AA { int member1; int member2; }; But this code gives an run time error, because variable "a" is used without being iniltialized!!! So my question is this: when we instantiate an int, it has a value. So why the default constructer doesn't work and by using those two int numbers initializes variable "a"??

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• PHP Variable from extended class

  - by Ste

  I cant retrieve var from parent class: class core { var $variable; var $test; function __construct() {} public function setVar($var) $this->variable = $var; } } class test extends core { public function getVar() { return $this->variable; //also if i echo here i can't see !!!! } } $core = new core(); $core->test = new test(); print $core->test->getVar(); Any help??

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• Call from a singleton class to a function which in turn calls that class's method

  - by dare2be

  Hello, I am still looking for a way to phrase it properly (I'm not a native speaker...). So I have this class SQL which implements the singleton pattern (for obvious reasons) and I also have this function, checkUsr(), which queries the database using one of SQL's methods. Everything works fine as long as I don't call checkUsr() from within the SQL class. When I do so, the scripts just exits and a blank page is displayed - no errors are returned, no exception is thrown... What's happening? And how do I work around this problem? EDIT: class SQL { public static function singleton() { static $instance; if(!isset($instance)) $instance = new SQL; return $instance; } public function tryLoginAuthor( $login, $sha1 ) { (...) } } function checkUsr() { if (!isset($_SESSION['login']) || !isset($_SESSION['sha1'])) throw new Exception('Not logged in', 1); $SQL = SQL::singleton(); $res = $SQL->tryLoginAuthor($_SESSION['login'], $_SESSION['sha1']); if (!isset($res[0])) throw new Exception('Not logged in', 1); }

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• Is there a straightforward way to have a thread-local instance variable?

  - by Dan Tao

  With the ThreadStatic attribute I can have a static member of a class with one instance of the object per thread. This is really handy for achieving thread safety using types of objects that don't guarantee thread-safe instance methods (e.g., System.Random). It only works for static members, though. Is there any straightforward way to declare a class member as thread-local, meaning, each class instance gets an object per thread?

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• How to use prepared statements (named parameters) on a php Class

  - by Mohamed Adib Errifai

  This is my first post here. I've searched in the site, but inforutunaly no matchs. Anyway, i want to know how to use named parameters on a class. so the pdo basic form is something like. $query = $bdd->prepare('SELECT * FROM table WHERE login = :login AND pww = :pww'); $query->execute(array('login' => $login, 'pww' => $pww)); and i want to integrate this on a class regardless of the number of parameters. Currently, i have this code http://pastebin.com/kKgSkaKt and for parameters, i use somethings like ( which is wrong and vulnerable to injection ) require_once 'classes/Mysql.class.php'; $mysql = new Mysql(); $sql = 'SELECT * FROM articles WHERE id = '.$_GET['id'].' LIMIT 1'; $data = $mysql->select($sql); And Thanks.

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• In Ruby, how to write a method to display any object's instance variable names and its values

  - by Jian Lin

  Given any object in Ruby (on Rails), how can I write a method so that it will display that object's instance variable names and its values, like this: @x: 1 @y: 2 @link_to_point: #<Point:0x10031b298 @y=20, @x=38> I also want to be able to print <br> to the end of each instance variable's value so as to print them out nicely on a webpage. the difficulty now seems to be that not every instance variable has an accessor, so it can't be called with obj.send(var_name) (the var_name has the "@" removed, so "@x" becomes "x")

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• how to create a dynamic class at runtime in Java

  - by Mrityunjay

  hi, is it possible to create a new java file from existing java file after changing some of its attributes at runtime?? Suppose i have a java file pubic class Student{ private int rollNo; private String name; // getters and setters // constructor } is it possible to create something like this, provided that rollNo is key element for the table.. public class Student { private StudentKey key; private String name; //getters and setters //constructor } public class StudentKey { private int rollNo; // getters and setters // construcotors } please help..

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• Implementation of interface when using child class of a parent class in method of interface

  - by dotnetdev

  I don't have access to my dev environment, but when I write the below: interface IExample void Test (HtmlControl ctrl); class Example : IExample { public void Test (HtmlTextArea area) { } I get an error stating the methods in the class implementation don't match the interface - so this is not possible. HtmlTextArea is a child class of HtmlControl, is there no way this is possible? I tried with .NET 3.5, but .NET 4.0 may be different (I am interested in any solution with either framework). Thanks

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• Create a class that inherets DrawableGameComponent in XNA as a CLASS with custom functions

  - by user3675013

  using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Media; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Content; namespace TileEngine { class Renderer : DrawableGameComponent { public Renderer(Game game) : base(game) { } SpriteBatch spriteBatch ; protected override void LoadContent() { base.LoadContent(); } public override void Draw(GameTime gameTime) { base.Draw(gameTime); } public override void Update(GameTime gameTime) { base.Update(gameTime); } public override void Initialize() { base.Initialize(); } public RenderTarget2D new_texture(int width, int height) { Texture2D TEX = new Texture2D(GraphicsDevice, width, height); //create the texture to render to RenderTarget2D Mine = new RenderTarget2D(GraphicsDevice, width, height); GraphicsDevice.SetRenderTarget(Mine); //set the render device to the reference provided //maybe base.draw can be used with spritebatch. Idk. We'll see if the order of operation //works out. Wish I could call base.draw here. return Mine; //I'm hoping that this returns the same instance and not a copy. } public void draw_texture(int width, int height, RenderTarget2D Mine) { GraphicsDevice.SetRenderTarget(null); //Set the renderer to render to the backbuffer again Rectangle drawrect = new Rectangle(0, 0, width, height); //Set the rendering size to what we want spriteBatch.Begin(); //This uses spritebatch to draw the texture directly to the screen spriteBatch.Draw(Mine, drawrect, Color.White); //This uses the color white spriteBatch.End(); //ends the spritebatch //Call base.draw after this since it doesn't seem to recognize inside the function //maybe base.draw can be used with spritebatch. Idk. We'll see if the order of operation //works out. Wish I could call base.draw here. } } } I solved a previous issue where I wasn't allowed to access GraphicsDevice outside the main Default 'main' class Ie "Game" or "Game1" etc. Now I have a new issue. FYi no one told me that it would be possible to use GraphicsDevice References to cause it to not be null by using the drawable class. (hopefully after this last bug is solved it doesn't still return null) Anyways at present the problem is that I can't seem to get it to initialize as an instance in my main program. Ie Renderer tileClipping; and I'm unable to use it such as it is to be noted i haven't even gotten to testing these two steps below but before it compiled but when those functions of this class were called it complained that it can't render to a null device. Which meant that the device wasn't being initialized. I had no idea why. It took me hours to google this. I finally figured out the words I needed.. which were "do my rendering in XNA in a seperate class" now I haven't used the addcomponent function because I don't want it to only run these functions automatically and I want to be able to call the custom ones. In a nutshell what I want is: *access to rendering targets and graphics device OUTSIDE default class *passing of Rendertarget2D (which contain textures and textures should automatically be passed with a rendering target? ) *the device should be passed to this function as well OR the device should be passed to this function as a byproduct of passing the rendertarget (which is automatically associated with the render device it was given originally) *I'm assuming I'm dealing with abstracted pointers here so when I pass a class object or instance, I should be recieving the SAME object , I referenced, and not a copy that has only the lifespan of the function running. *the purpose for all these options: I want to initialize new 2d textures on the fly to customize tileclipping and even the X , y Offsets of where a WHOLE texture will be rendered, and the X and Y offsets of where tiles will be rendered ON that surface. This is why. And I'll be doing region based lighting effects per tile or even per 8X8 pixel spaces.. we'll see I'll also be doing sprite rotations on the whole texture then copying it again to a circular masked texture, and then doing a second copy for only solid tiles for masked rotated collisions on sprites. I'll be checking the masked pixels for my collision, and using raycasting possibly to check for collisions on those areas. The sprite will stay in the center, when this rotation happens. Here is a detailed diagram: http://i.stack.imgur.com/INf9K.gif I'll be using texture2D for steps 4-6 I suppose for steps 1 as well. Now ontop of that, the clipping size (IE the sqaure rendered) will be able to be shrunk or increased, on a per frame basis Therefore I can't use the same static size for my main texture2d and I can't use just the backbuffer Or we get the annoying flicker. Also I will have multiple instances of the renderer class so that I can freely pass textures around as if they are playing cards (in a sense) layering them ontop of eachother, cropping them how i want and such. and then using spritebatch to simply draw them at the locations I want. Hopefully this makes sense, and yes I will be planning on using alpha blending but only after all tiles have been drawn.. The masked collision is important and Yes I am avoiding using math on the tile rendering and instead resorting to image manipulation in video memory which is WHY I need this to work the way I'm intending it to work and not in the default way that XNA seems to handle graphics. Thanks to anyone willing to help. I hate the code form offered, because then I have to rely on static presence of an update function. What if I want to kill that update function or that object, but have it in memory, but just have it temporarily inactive? I'm making the assumption here the update function of one of these gamecomponents is automatic ? Anyways this is as detailed as I can make this post hopefully someone can help me solve the issue. Instead of tell me "derrr don't do it this wayyy" which is what a few people told me (but they don't understand the actual goal I have in mind) I'm trying to create basically a library where I can copy images freely no matter the size, i just have to specify the size in the function then as long as a reference to that object exists it should be kept alive? right? :/ anyways.. Anything else? I Don't know. I understand object oriented coding but I don't understand this XNA It's beggining to feel impossible to do anything custom in it without putting ALL my rendering code into the draw function of the main class tileClipping.new_texture(GraphicsDevice, width, height) tileClipping.Draw_texture(...)

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• Create object of unknown class (two inherited classes)

  - by Paul

  I've got the following classes: class A { void commonFunction() = 0; } class Aa: public A { //Some stuff... } class Ab: public A { //Some stuff... } Depending on user input I want to create an object of either Aa or Ab. My imidiate thought was this: A object; if (/*Test*/) { Aa object; } else { Ab object; } But the compiler gives me: error: cannot declare variable ‘object’ to be of abstract type ‘A’ because the following virtual functions are pure within ‘A’: //The functions... Is there a good way to solve this?

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• C# Function Inheritance--Use Child Class Vars with Base Class Function

  - by Sean O'Connor

  Good day, I have a fairly simple question to experienced C# programmers. Basically, I would like to have an abstract base class that contains a function that relies on the values of child classes. I have tried code similar to the following, but the compiler complains that SomeVariable is null when SomeFunction() attempts to use it. Base class: public abstract class BaseClass { protected virtual SomeType SomeVariable; public BaseClass() { this.SomeFunction(); } protected void SomeFunction() { //DO SOMETHING WITH SomeVariable } } A child class: public class ChildClass:BaseClass { protected override SomeType SomeVariable=SomeValue; } Now I would expect that when I do: ChildClass CC=new ChildClass(); A new instance of ChildClass should be made and CC would run its inherited SomeFunction using SomeValue. However, this is not what happens. The compiler complains that SomeVariable is null in BaseClass. Is what I want to do even possible in C#? I have used other managed languages that allow me to do such things, so I certain I am just making a simple mistake here. Any help is greatly appreciated, thank you.

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• OBJ-C - Getting a class name from a class hierarchy

  - by mmmilo

  Let's say I have the following headers: @interface SuperClass : NSObject @interface SubClass : SuperClass I'm alloc'ing an instance of the class by doing: SubClass *sc = [[SubClass alloc] init]; In my SuperClass.m: - (id) init { self = [super init]; if (self != nil) { NSString *cString = NSStringFromClass([self class]); } return self; } Simple, right? My question is: how can I get cString to return the SuperClass class, rather than the SubClass class? Since the SubClass is alloc'd/init'd, is this not possible? Thanks!

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• ActionScript Custom Class With Return Type?

  - by TheDarkIn1978

  i just know this is a dumb question, so excuse me in advance. i want to essentially classify a simple function in it's own .as file. the function compares integers. but i don't know how to call the class and receive a boolean return. here's my class package { public class CompareInts { public function CompareInts(small:int, big:int) { compare(small, big); } private function compare(small:int, big:int):Boolean { if (small < big) return true; else return false; } } } so now i'd like to write something like this: if (CompareInts(1, 5) == true). or output 'true' by writing trace(CompareInts(1, 5));

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• PHP: reusing database class

  - by citricsquid

  Hi, I built a class that allows me to do: $db->query($query); and it works perfectly, although if I want to do: $db->query($query); while($row = $db->fetch_assoc()){ $db->query($anotherquery); echo $db->result(); } it "breaks" the class. I don't want to constantly have to redeclare my class (eg: $seconddb = new database()), is there a way to get around this? I want to be able to reuse $db within $db, without overwriting the "outside" db. currently I'm create an array of data (from db-fetch_assoc() then doing a foreach and then doing the db call inside that: $db->query('SELECT * FROM table'); while($row = $db->fetch_assoc()){ $arr[] = $row; } foreach($arr as $a){ $db->query(); // query and processing here } Is this the best method or am I missing the obvious? Should I consider passing a connection link ID with the database connection?

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• Java : Using parent class method to access child class variable

  - by Jayant

  I have the following scenario : public class A { private int x = 5; public void print() { System.out.println(x); } } public class B extends A { private int x = 10; /*public void print() { System.out.println(x); }*/ public static void main(String[] args) { B b = new B(); b.print(); } } On executing the code, the output is : 5. How to access the child class(B's) variable(x) via the parent class method? Could this be done without overriding the print() method (i.e. uncommenting it in B)? [This is important because on overriding we will have to rewrite the whole code for the print() method again]

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• Preventing SQL injecting in a database class

  - by Josh

  I'm building a database class and thought it'd be a good idea to incorporate some form of SQL injection prevention (duh!). Here's the method that runs a database query: class DB { var $db_host = 'localhost'; var $db_user = 'root'; var $db_passwd = ''; var $db_name = 'whatever'; function query($sql) { $this->result = mysql_query($sql, $this->link); if(!$this->result) { $this->error(mysql_error()); } else { return $this->result; } } } There's more in the class than that but I'm cutting it down just for this. The problem I'm facing is if I just use mysql_real_escape_string($sql, $this->link); then it escapes the entire query and leads to a SQL syntax error. How can I dynamically find the variables that need to be escaped? I want to avoid using mysql_real_escape_string() in my main code blocks, i'd rather have it in a function. Thanks.

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