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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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  • c struct question

    - by lhw
    Hi, I'm trying to implement a simple priority queue from array of queues. I'm trying to define a struct queue, and than a struct priority queue that has an array of queues as its member variable. However, when I try to compile the code, I get the following error: pcb.h:30: error: array type has incomplete element type The code is below: typedef struct{ pcb *head; pcb *tail; SINT32 size; } pcb_Q; typedef struct { struct pcb_Q queues[5]; SINT32 size; } pcb_pQ; Could someone give me a hand? Thanks a lot.

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Python Class Variables Question

    - by zyq524
    I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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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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  • VS 11 Beta merge tool is awesome, except for resovling conflicts

    - by deadlydog
    If you've downloaded the new VS 11 Beta and done any merging, then you've probably seen the new diff and merge tools built into VS 11.  They are awesome, and by far a vast improvement over the ones included in VS 2010.  There is one problem with the merge tool though, and in my opinion it is huge.Basically the problem with the new VS 11 Beta merge tool is that when you are resolving conflicts after performing a merge, you cannot tell what changes were made in each file where the code is conflicting.  Was the conflicting code added, deleted, or modified in the source and target branches?  I don't know (without explicitly opening up the history of both the source and target files), and the merge tool doesn't tell me.  In my opinion this is a huge fail on the part of the designers/developers of the merge tool, as it actually forces me to either spend an extra minute for every conflict to view the source and target file history, or to go back to use the merge tool in VS 2010 to properly assess which changes I should take.I submitted this as a bug to Microsoft, but they say that this is intentional by design. WHAT?! So they purposely crippled their tool in order to make it pretty and keep the look consistent with the new diff tool?  That's like purposely putting a little hole in the bottom of your cup for design reasons to make it look cool.  Sure, the cup looks cool, but I'm not going to use it if it leaks all over the place and doesn't do the job that it is intended for. Bah! but I digress.Because this bug is apparently a feature, they asked me to open up a "feature request" to have the problem fixed. Please go vote up both my bug submission and the feature request so that this tool will actually be useful by the time the final VS 11 product is released.

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  • Do I need to manually create indexes for a DBIx::Class belongs_to relationship

    - by Dancrumb
    I'm using the DBIx::Class modules for an ORM approach to an application I have. I'm having some problems with my relationships. I have the following package MySchema::Result::ClusterIP; use strict; use warnings; use base qw/DBIx::Class::Core/; our $VERSION = '1.0'; __PACKAGE__->load_components(qw/InflateColumn::Object::Enum Core/); __PACKAGE__->table('cluster_ip'); __PACKAGE__->add_columns( # Columns here ); __PACKAGE__->set_primary_key('objkey'); __PACKAGE__->belongs_to( 'configuration' => 'MySchema::Result::Configuration', 'config_key'); __PACKAGE__->belongs_to( 'cluster' => 'MySchema::Result::Cluster', { 'foreign.config_key' => 'self.config_key', 'foreign.id' => 'self.cluster_id' } ); As well as package MySchema::Result::Cluster; use strict; use warnings; use base qw/DBIx::Class::Core/; our $VERSION = '1.0'; __PACKAGE__->load_components(qw/InflateColumn::Object::Enum Core/); __PACKAGE__->table('cluster'); __PACKAGE__->add_columns( # Columns here ); __PACKAGE__->set_primary_key('objkey'); __PACKAGE__->belongs_to( 'configuration' => 'MySchema::Result::Configuration', 'config_key'); __PACKAGE__->has_many('cluster_ip' => 'MySchema::Result::ClusterIP', { 'foreign.config_key' => 'self.config_key', 'foreign.cluster_id' => 'self.id' }); There are a couple of other modules, but I don't believe that they are relevant. When I attempt to deploy this schema, I get the following error: DBIx::Class::Schema::deploy(): DBI Exception: DBD::mysql::db do failed: Can't create table 'test.cluster_ip' (errno: 150) [ for Statement "CREATE TABLE `cluster_ip` ( `objkey` smallint(5) unsigned NOT NULL auto_increment, `config_key` smallint(5) unsigned NOT NULL, `cluster_id` char(16) NOT NULL, INDEX `cluster_ip_idx_config_key_cluster_id` (`config_key`, `cluster_id`), INDEX `cluster_ip_idx_config_key` (`config_key`), PRIMARY KEY (`objkey`), CONSTRAINT `cluster_ip_fk_config_key_cluster_id` FOREIGN KEY (`config_key`, `cluster_id`) REFERENCES `cluster` (`config_key`, `id`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `cluster_ip_fk_config_key` FOREIGN KEY (`config_key`) REFERENCES `configuration` (`config_key`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB"] at test_deploy.pl line 18 (running "CREATE TABLE `cluster_ip` ( `objkey` smallint(5) unsigned NOT NULL auto_increment, `config_key` smallint(5) unsigned NOT NULL, `cluster_id` char(16) NOT NULL, INDEX `cluster_ip_idx_config_key_cluster_id` (`config_key`, `cluster_id`), INDEX `cluster_ip_idx_config_key` (`config_key`), PRIMARY KEY (`objkey`), CONSTRAINT `cluster_ip_fk_config_key_cluster_id` FOREIGN KEY (`config_key`, `cluster_id`) REFERENC ES `cluster` (`config_key`, `id`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `cluster_ip_fk_config_key` FOREIGN KEY (`config_key`) REFERENCES `configuration` (`conf ig_key`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB") at test_deploy.pl line 18 From what I can tell, MySQL is complaining about the FOREIGN KEY constraint, in particular, the REFERENCE to (config_key, id) in the cluster table. From my reading of the MySQL documentation, this seems like a reasonable complaint, especially in regards to the third bullet point on this doc page. Here's my question. Am I missing something in the DBIx::Class module? I realize that I could explicitly create the necessary index to match up with this foreign key constraint, but that seems to be repetitive work. Is there something I should be doing to make this occur implicitly?

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  • Overriding GetHashCode in a mutable struct - What NOT to do?

    - by Kyle Baran
    I am using the XNA Framework to make a learning project. It has a Point struct which exposes an X and Y value; for the purpose of optimization, it breaks the rules for proper struct design, since its a mutable struct. As Marc Gravell, John Skeet, and Eric Lippert point out in their respective posts about GetHashCode() (which Point overrides), this is a rather bad thing, since if an object's values change while its contained in a hashmap (ie, LINQ queries), it can become "lost". However, I am making my own Point3D struct, following the design of Point as a guideline. Thus, it too is a mutable struct which overrides GetHashCode(). The only difference is that mine exposes and int for X, Y, and Z values, but is fundamentally the same. The signatures are below: public struct Point3D : IEquatable<Point3D> { public int X; public int Y; public int Z; public static bool operator !=(Point3D a, Point3D b) { } public static bool operator ==(Point3D a, Point3D b) { } public Point3D Zero { get; } public override int GetHashCode() { } public override bool Equals(object obj) { } public bool Equals(Point3D other) { } public override string ToString() { } } I have tried to break my struct in the way they describe, namely by storing it in a List<Point3D>, as well as changing the value via a method using ref, but I did not encounter they behavior they warn about (maybe a pointer might allow me to break it?). Am I being too cautious in my approach, or should I be okay to use it as is?

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  • How can I malloc an array of struct to do the following using file operation?

    - by RHN
    How can malloc an array of struct to do the following using file operation? the file is .txt input in the file is like: 10 22 3.3 33 4.4 I want to read the first line from the file and then I want to malloc an array of input structures equal to the number of lines to be read in from the file. Then I want to read in the data from the file and into the array of structures malloc. Later on I want to store the size of the array into the input variable size. return an array.After this I want to create another function that print out the data in the input variable in the same form like input file and suppose a function call clean_data will free the malloc memory at the end. I have tried somthing like: struct input { int a; float b,c; } struct input* readData(char *filename,int *size); int main() { return 0; } struct input* readData(char *filename,int *size) { char filename[] = "input.txt"; FILE *fp = fopen(filename, "r"); int num; while(!feof(fp)) { fscanf(fp,"%f", &num); struct input *arr = (struct input*)malloc(sizeof(struct input)); } }

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  • How to get actual type of an derived class from its parent interface

    - by Tarik
    Hello people, Lets say we have a code portion like this : IProduct product = ProductCreator.CreateProduct(); //Factory Method we have here SellThisProduct(product); //... private void SellThisProduct(IProduct product) { //..do something here } //... internal class Soda : IProduct {} internal class Book : IProduct {} How can I infer which product is actually passed into SellThisProduct() method in the method? I think if I say GetType() or something it will probably return the IProduct type. Thanks...

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  • Generating Class Diagram

    - by GustlyWind
    HI All I am at the end of the release of my project.So in order to keep working our manger asked us to generate Class Diagrams for the code we had written.Its medium project with 3500 java files .So I think we need to generate class diagrams.First I need to know how reverse engineering works here. Also I looked for some tools in Google(Green, Violet) but not sure whether they are of any help.Please suggest me how to proceed.Also a good beginning tutorial is appreciated.

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  • Best way to define an immutable class in Objective C

    - by Patrick Marty
    Hi, I am a newbie in Objective C and I was wondering what is the best way to define an immutable class in Objective-C (like NSString for example). I want to know what are the basic rules one has to follow to make a class immutable. I think that : setters shouldn't be provided if properties are used, they should be readonly accessInstanceVariablesDirectly must be override and return NO Did I forget something ? Thanks

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  • Append class="external" to external links.

    - by K3
    What is the php code to append class="external" to links that are posted and are not the domain. For example my site is www.mysite.com and you post a link to www.mysite.com/news and a link to www.yoursite.com How do I set it so only non "mysite.com" links have the class specified?

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