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  • Why does forward declaration not work with classes?

    - by eSKay
    int main() { B bb; //does not compile (neither does class B bb;) C cc; //does not compile struct t tt; //compiles class B {}; struct s { struct t * pt; }; //compiles struct t { struct s * ps; }; return 0; } class C {}; I just modified the example given here. Why is that the struct forward declarations work but not the class forward declarations? Does it have something to do with the namespaces - tag namespace and typedef namespace? I know that the structure definitions without typedefs go to tag namespace. Structures are just classes with all public members. So, I expect them to behave similarly.

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  • Problem using in GWT project classes from other project/source folders

    - by voipsecuritydigest.com
    My project contains 2 source folder, one is generic J2EE application another is smartCleintGWT, I want to use some already existing DTO classes from first source folder (src) Note that class used on client side and on server side of GWT project! When I do that I getting error [ERROR] Errors in 'file:/C:/..Projects/Admin/DMX/src_console/com/ho/nod/client/AdminRPC.java' [ERROR] Line 7: No source code is available for type com.dmx.synch.server.descriptors.DMXLicense; did you forget to inherit a required module? Source is available obviously; is there any way to import all that into GWT? PS In the future 2 source folder will be separated into 2 projects...I hope it wont be that complicated as well.

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  • Can you select an element with two classes in jQuery

    - by Petras
    I have an element that has two classes but can't seem to select it with jQuery. Is it possible. Here's the code: <html> <head runat="server"> <script type="text/javascript" src="abc/scripts/jquery-1.4.2.min.js"></script> <script type="text/javascript"> $(document).ready(function() { alert($(".x.y").html()); //shows null, I want it to show "456" }); </script> </head> <body> <div class="x" class"y">456</div> </body> </html>

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  • C++ Template Classes Circular Dependency Problem

    - by TomWij
    We have two classes: template<typename T, typename Size, typename Stack, typename Sparse> class Matrix and template<typename T, typename Size> class Iterator Matrix should be able to return begin and end iterators and Iterator will keep a referrence to the Matrix to access the elements via it's interface. We don't want Iterator to depend on the internal storage of the Matrix to prevent coupling. How can we solve this cyclic dependency problem? (The internal Storage class has the same template parameters as the Matrix class and the same access procedures as the Matrix itself)

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  • Declare two classes from eachother.

    - by tumba25
    I'm writing a app in NetBeans. I have two classes MyApp_View and MyApp_Functions. The MyApp_View class starts like this public class MyApp_View extends FrameView { MyApp_Functions My_functions = new MyApp_Functions(); public MyApp_View(SingleFrameApplication app) { super(app); In MyApp_Functions I have MyApp_View my_view = new MyApp_View(null); I want to access the public variables in MyApp_View from MyApp_Functions and the public methods in functions from view, but have no success with this. Is this doable? And how?

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  • Beginner having a problem with classes

    - by David
    I'm working through O'Reilly's "Learning Python" and having a problem with classes. I think I understand the concept, but in practice have stumbled upon this problem. Fron page 88-89: >>> class Worker: def __innit__(self, name, pay): self.name=name self.pay=pay def lastName(self): return self.name.split()[-1] def giveRaise(self, percent): self.pay*=(1.0+percent) Then the book says "Calling the class like a function generates instances of a new type ...etc" and gives this example. bob = Worker('Bob Smith', 50000) This gives me this error: TypeError: this constructor takes no arguments. And then I start muttering profanities. So what am I doing wrong here? Thanks for the help.

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  • AS3 Memory management when instantiating extended classes

    - by araid
    I'm developing an AS3 application which has some memory leaks I can't find, so I'd like to ask some newbie questions about memory management. Imagine I have a class named BaseClass, and some classes that extend this one, such as ClassA, ClassB, etc. I declare a variable: myBaseClass:BaseClass = new ClassA(); After a while, I use it to instantiate a new object: myBaseClass = new ClassB(); some time after myBaseClass = new ClassC(); and the same thing keeps happening every x millis, triggered by a timer. Is there any memory problem here? Are the unused instances correctly deleted by the garbage collector? Thanks!

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  • Python New-style Classes and the Super Function

    - by sfjedi
    This is not the result I expect to see: class A(dict): def __init__(self, *args, **kwargs): self['args'] = args self['kwargs'] = kwargs class B(A): def __init__(self, *args, **kwargs): super(B, self).__init__(args, kwargs) print 'Instance A:', A('monkey', banana=True) #Instance A: {'args': ('monkey',), 'kwargs': {'banana': True}} print 'Instance B:', B('monkey', banana=True) #Instance B: {'args': (('monkey',), {'banana': True}), 'kwargs': {}} I'm just trying to get classes A and B to have consistent values set. I'm not sure why the kwargs are being inserted into the args, but I'm to presume I am either calling init() wrong from the subclass or I'm trying to do something that you just can't do. Any tips?

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  • problems with extended classes and overwrite with methods

    - by Marco
    I have a .net website written in C# and will make functionalities that other developers can use. So i will make some default implementation and a developer can overwrite some methods Example: i have a class ShoppingCart and a class Product the class product haves a method getProductPrice the shoppingcart will call the method getProductPrice for calculating the total price of cart The Shoppingcart and Product are in the same project and i will give the developers the .dll so they can't change the source code so we can update the assembly later So they need to make a other project and extend the product class and overwrite the method getProductPrice so they can implement there own logic The problem is that the shoppingcart will not call the extended method but the original If we make already a extended project for the developers and the shoppingcart will call the extended method then we have a circular reference because the extended product needs a reference to product and the shopping cart to the extended product partial classes also don't works because we only can use partials within the same assembly anyone a suggestion ? thanks in advance

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  • migrating C++ code from structures to classes

    - by eSKay
    I am migrating some C++ code from structures to classes. I was using structures mainly for bit-field optimizations which I do not need any more (I am more worried about speed than saving space now). What are the general guidelines for doing this migration? I am still in the planning stage as this is a very big move affecting a major part of the code. I want to plan everything first before doing it. What are all the essential things I should keep in mind?

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  • FindBugs and CheckForNull on classes vs. interfaces

    - by ndn
    Is there any way to let FindBugs check and warn me if a CheckForNull annotation is present on the implementation of a method in a class, but not on the declaration of the method in the interface? import javax.annotation.CheckForNull; interface Foo { public String getBar(); } class FooImpl implements Foo { @CheckForNull @Override public String getBar() { return null; } } public class FindBugsDemo { public static void main(String[] args) { Foo foo = new FooImpl(); System.out.println(foo.getBar().length()); } } I just discovered a bug in my application due to a missing null check that was not spotted by FindBugs because CheckForNull was only present on FooImpl, but not on Foo, and I don't want to spot all other locations of this problem manually.

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  • Python many-to-one mapping (creating equivalence classes)

    - by Adam Matan
    Hi, I have a project of converting one database to another. One of the original database columns defines the row's category. This coulmn should be mapepd to a new category in the new databse. For example, let's assume the original categories are:parrot, spam, cheese_shop, Cleese, Gilliam, Palin Now that's a little verbose for me, And I want to have these rows categorized as sketch, actor - That is, define all the sketches and all the actors as two equivalence classes. >>> monty={'parrot':'sketch', 'spam':'sketch', 'cheese_shop':'sketch', 'Cleese':'actor', 'Gilliam':'actor', 'Palin':'actor'} >>> monty {'Gilliam': 'actor', 'Cleese': 'actor', 'parrot': 'sketch', 'spam': 'sketch', 'Palin': 'actor', 'cheese_shop': 'sketch'} That's quite awkward- I would prefer having something like: monty={ ('parrot','spam','cheese_shop'): 'sketch', ('Cleese', 'Gilliam', 'Palin') : 'actors'} But this, of course, sets the entire tuple as a key: >>> monty['parrot'] Traceback (most recent call last): File "<pyshell#29>", line 1, in <module> monty['parrot'] KeyError: 'parrot' Any ideas how to create an elegant many-to-one dictionary in Python? Thanks, Adam

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  • Obj-C: Passing pointers to initialized classes in other classes

    - by FnGreg7
    Hey all. I initialized a class in my singleton called DataModel. Now, from my UIViewController, when I click a button, I have a method that is trying to access that class so that I may add an object to one of its dictionaries. My get/set method passes back the pointer to the class from my singleton, but when I am back in my UIViewController, the class passed back doesn't respond to methods. It's like it's just not there. I think it has something to do with the difference in passing pointers around classes or something. I even tried using the copy method to throw a copy back, but no luck. UIViewController: ApplicationSingleton *applicationSingleton = [[ApplicationSingleton alloc] init]; DataModel *dataModel = [applicationSingleton getDataModel]; [dataModel retrieveDataCategory:dataCategory]; Singleton: ApplicationSingleton *m_instance; DataModel *m_dataModel; - (id) init { NSLog(@"ApplicationSingleton.m initialized."); self = [super init]; if(self != nil) { if(m_instance != nil) { return m_instance; } NSLog(@"Initializing the application singleton."); m_instance = self; m_dataModel = [[DataModel alloc] init]; } NSLog(@"ApplicationSingleton init method returning."); return m_instance; } -(DataModel *)getDataModel { DataModel *dataModel_COPY = [m_dataModel copy]; return dataModel_COPY; } For the getDataModel method, I also tried this: -(DataModel *)getDataModel { return m_dataModel; } In my DataModel retrieveDataCategory method, I couldn't get anything to work. I even just tried putting a NSLog in there but it never would come onto the console. Any ideas?

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  • What are the steps to grouping related classes into packages

    - by user2368481
    I've been googling this for some time, but what I haven't found are the clear steps needed to be taken to group related classes into packages in Java. In my case, I have about a number of .java files that I'd like to group into 3 packages according to the MVC pattern. One package for Model classes, one package for View classes and one package for Controller classes. I've identified which belong in what package, but not sure of the next step.

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  • Variables in static library are never initialized. Why?

    - by Coyote
    I have a bunch of variables that should be initialized then my game launches, but must of them are never initialized. Here is an example of the code: MyClass.h class MyClass : public BaseObject { DECLARE_CLASS_RTTI(MyClass, BaseObject); ... }; MyClass.cpp REGISTER_CLASS(MyClass) Where REGISTER_CLASS is a macro defined as follow #define REGISTER_CLASS(className)\ class __registryItem##className : public __registryItemBase {\ virtual className* Alloc(){ return NEW className(); }\ virtual BaseObject::RTTI& GetRTTI(){ return className::RTTI; }\ }\ \ const __registryItem##className __registeredItem##className(#className); and __registryItemBase looks like this: class __registryItemBase { __registryItemBase(const _string name):mName(name){ ClassRegistry::Register(this); } const _string mName; virtual BaseObject* Alloc() = 0; virtual BaseObject::RTTI& GetRTTI() = 0; } Now the code is similar to what I currently have and what I have works flawlessly, all the registered classes are registered to a ClassManager before main(...) is called. I'm able to instantiate and configure components from scripts and auto-register them to the right system etc... The problem arrises when I create a static library (currently for the iPhone, but I fear it will happen with android as well). In that case the code in the .cpp files is never registered. Why is the resulting code not executed when it is in the library while the same code in the program's binary is always executed? Bonus questions: For this to work in the static library, what should I do? Is there something I am missing? Do I need to pass a flag when building the lib? Should I create another structure and init all the __registeredItem##className using that structure?

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  • What are the differences between abstract classes, interfaces, and when to use them

    - by user66662
    Recently I have started to wrap my head around OOP, and I am now to the point where the more I read about the differences between Abstract classes and Interfaces the more confused I become. So far, neither can be instantiated. Interfaces are more or less structural blueprints that determine the skeleton and abstracts are different by being able to partially develop code. I would like to learn more about these through my specific situation. Here is a link to my first question if you would like a little more background information: What is a good design model for my new class? Here are two classes I created: class Ad { $title; $description $price; function get_data($website){ } function validate_price(){ } } class calendar_event { $title; $description $start_date; function get_data($website){ //guts } function validate_dates(){ //guts } } So, as you can see these classes are almost identical. Not shown here, but there are other functions, like get_zip(), save_to_database() that are common across my classes. I have also added other classes Cars and Pets which have all the common methods and of course properties specific to those objects (mileage, weight, for example). Now I have violated the DRY principle and I am managing and changing the same code across multiple files. I intend on having more classes like boats, horses, or whatever. So is this where I would use an interface or abstract class? From what I understand about abstract classes I would use a super class as a template with all of the common elements built into the abstract class, and then add only the items specifically needed in future classes. For example: abstract class content { $title; $description function get_data($website){ } function common_function2() { } function common_function3() { } } class calendar_event extends content { $start_date; function validate_dates(){ } } Or would I use an interface and, because these are so similar, create a structure that each of the subclasses are forced to use for integrity reasons, and leave it up to the end developer who fleshes out that class to be responsible for each of the details of even the common functions. my thinking there is that some 'common' functions may need to be tweaked in the future for the needs of their specific class. Despite all that above, if you believe I am misunderstanding the what and why of abstracts and interfaces altogether, by all means let a valid answer to be stop thinking in this direction and suggest the proper way to move forward! Thanks!

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  • Using nested public classes to organize constants

    - by FrustratedWithFormsDesigner
    I'm working on an application with many constants. At the last code review it came up that the constants are too scattered and should all be organized into a single "master" constants file. The disagreement is about how to organize them. The majority feel that using the constant name should be good enough, but this will lead to code that looks like this: public static final String CREDITCARD_ACTION_SUBMITDATA = "6767"; public static final String CREDITCARD_UIFIELDID_CARDHOLDER_NAME = "3959854"; public static final String CREDITCARD_UIFIELDID_EXPIRY_MONTH = "3524"; public static final String CREDITCARD_UIFIELDID_ACCOUNT_ID = "3524"; ... public static final String BANKPAYMENT_UIFIELDID_ACCOUNT_ID = "9987"; I find this type of naming convention to be cumbersome. I thought it might be easier to use public nested class, and have something like this: public class IntegrationSystemConstants { public class CreditCard { public static final String UI_EXPIRY_MONTH = "3524"; public static final String UI_ACCOUNT_ID = "3524"; ... } public class BankAccount { public static final String UI_ACCOUNT_ID = "9987"; ... } } This idea wasn't well received because it was "too complicated" (I didn't get much detail as to why this might be too complicated). I think this creates a better division between groups of related constants and the auto-complete makes it easier to find these as well. I've never seen this done though, so I'm wondering if this is an accepted practice or if there's better reasons that it shouldn't be done.

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  • Static method not called

    - by Smile
    I'm trying to call a static method (printABC()) in this class but it's not working. If I uncomment both of the lines marked T_T (1 and 2), it works! Why does it fail with only one of the lines? import java.util.Scanner; class pro0009 { static Scanner in = new Scanner(System.in); static int A,B,C; static void printABC(){ String ABC = in.nextLine(); ABC=ABC.replace("A"," "+A+" "); ABC=ABC.replace("B"," "+B+" "); ABC=ABC.replace("C"," "+C+" "); //System.out.print(ABC.substring(1)); System.out.print(ABC); } public static void main(String[] args){ int x = in.nextInt(); //1 int y = in.nextInt(); //2 int z = in.nextInt(); //3 if(x<y){//1<2 if(x<z){ //1<3 if(y<z){//x<y<z 2<3 //1<2<3 A=x; B=y; C=z; printABC();//T_T 1 System.out.println("Here"); //pro0009.printABC();//T_T 2 //System.out.println("Here2"); }else{ //x<z<y A=x; B=z; C=y; } }else{//z<x<y A=z; B=x; C=y; } }else{//y<x if(y<z){ if(x<z){//y<x<z A=y; B=x; C=z; }else{//y<z<x A=y; B=z; C=x; } }else{//z<y<x A=z; B=y; C=x; } } } }

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  • Interface Builder can't see classes in a static library

    - by teabot
    I have refactored some UIView sub-classes into a static library. However, when using Interface Builder to create view components for a project that uses the static library I find that it is unaware of the library classes. What do I need to do to make the class interfaces visible to Interface Builder? Update: The correct answer refers to dragging the headers into the 'XIB browser'. The '.h' files can be dragged from a finder window to the window area identified in this image:

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  • Accessing Static Methods on a Generic class in c#

    - by mrlane
    Hello, I have the following situation in code, which I suspect may be a bit dodgey: I have a class: abstract class DataAccessBase<T> : IDataAccess where T : AnotherAbstractClass This class DataAccessBase also has a static factory method which creates instances of derived classes of itself using an enum value in a which statement to decide which derived type to create: static IDataAccess CreateInstance(TypeToCreateEnum) Now, the types derived from DataAccessBase<T> are themselves NOT generic, they specify a type for T: class PoLcZoneData : DataAccessBase<PoLcZone> // PoLcZone is derived from AnotherAbstractClass So far I am not sure if this is pushing the limits of good use of generics, but what I am really concerned about is how to access the static CreateInstance() method in the first place: The way I am doing this at the moment is to simply pass any type T where T : AnotherAbstractClass. In particular I am passing AnotherAbstractClass itself. This allows compilation just fine, but it does seem to me that passing any type to a generic class just to get at the statics is a bit dodgey. I have actually simplified the situation somewhat as DataAccessBase<T> is the lower level in the inheritance chain, but the static factory methods exists in a middle tier with classes such as PoLcZoneData being the most derived on the only level that is not generic. What are peoples thoughts on this arrangement?

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  • Thread-safe initialization of function-local static const objects

    - by sbi
    This question made me question a practice I had been following for years. For thread-safe initialization of function-local static const objects I protect the actual construction of the object, but not the initialization of the function-local reference referring to it. Something like this: namspace { const some_type& create_const_thingy() { lock my_lock(some_mutex); static const some_type the_const_thingy; return the_const_thingy; } } void use_const_thingy() { static const some_type& the_const_thingy = create_const_thingy(); // use the_const_thingy } The idea is that locking takes time, and if the reference is overwritten by several threads, it won't matter. I'd be interested if this is safe enough in practice? safe according to The Rules? (I know, the current standard doesn't even know what "concurrency" is, but what about trampling over an already initialized reference? And do other standards, like POSIX, have something to say that's relevant to this?) For the inquiring minds: Many such function-local static const objects I used are maps which are initialized from const arrays upon first use and used for lookup. For example, I have a few XML parsers where tag name strings are mapped to enum values, so I could later switch over the tags enum values.

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  • Advice/suggestions for my first project PHP Classes

    - by Philip
    Hi guys, Any advice is welcome! I have a very limited understanding of php classes but below is my starting point for the route I would like to take. The code is a reflection of what I see in my head and how I would like to go about business. Does my code even look ok, or am I way off base? What are your thoughts, how would you go about achieving such a task as form-validate-insertquery-sendmail-return messages and errors? Please try and keep your answers simple enough for me to digest as for me its about understanding whats going on and not just a copy/paste job. Kindest regards, Phil. Note: This is a base structure only, no complete code added. <?php //======================================= //class.logging.php //======================================== class logging { public $data = array(); public $errors = array(); function __construct() { array_pop($_POST); $this->data =($this->_logging)? is_isset(filterStr($_POST) : ''; foreach($this->data as $key=> $value) { $this->data[$key] = $value; } //print_r($this->data); de-bugging } public function is_isset($str) { if(isset($str)) ? true: false; } public function filterStr($str) { return preg_match(do somthing, $str); } public function validate_post() { try { if(!is_numeric($data['cardID'])) ? throw new Exception('CardID must be numeric!') : continue; } catch (Exception $e) { return $errors = $e->getCode(); } } public function showErrors() { foreach($errors as $error => $err) { print('<div class="notok"></div><br />'); } } public function insertQ() { $query = ""; } } //======================================= //Usercp.php //======================================== if(isset($_GET['mode'])) { $mode = $_GET['mode']; } else { $mode = 'usercp'; } switch($mode) { case 'usercp': echo 'Welcome to the User Control Panel'; break; case 'logging': require_once 'class.logging.php'; $logger = new logging(); if(isset($_POST['submit']) { if($logger->validate_post === true) { $logger->insertQ(); require_once '/scripts/PHPMailer/class.phpmailer.php'; $mailer = new PHPMailer(); $mailer->PHPMailer(); } else { echo ''.$logger->showErrors.''; } } else { echo ' <form action="'.$_SERVER['PHP_SELF'].'?mode=logging" method="post"> </form> '; } break; case 'user_logout': // do somthing break; case 'user_settings': // do somthing break; ?>

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  • Categories in static library for iPhone device 3.0

    - by Nick
    I have categories in my static library. Any application developer should set -ObjC flag to "Other Linker Flags" to use my static library properly. It works fine for iPhone device/iPhone Simulator 2.x and iPhone Simulator 3.0. But it crashes for iPhone device 3.0. As written in this article it is new linker bug. They suggest to use one more linker flag: -all_load. But when I add this flag, build fails too, because there are duplicate symbols. How to use categories in static libraries for iPhone device 3.0? Any suggestions?

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  • DLL export of a static function

    - by Begbie00
    Hi all - I have the following static function: static inline HandVal StdDeck_StdRules_EVAL_N( StdDeck_CardMask cards, int n_cards ) Can I export this function in a DLL? If so, how? Thanks, Mike Background information: I'm doing this because the original source code came with a VS project designed to compile as a static (.lib) library. In order to use ctypes/Python, I'm converting the project to a DLL. I started a VS project as a DLL and imported the original source code. The project builds into a DLL, but none of the functions (including functions such as the one listed above) are exported (as confirmed by both the absence of dllexport in the source code and tools such as DLL Export Viewer). I tried to follow the general advice here (create an exportable wrapper function within the header) to no avail...functions still don't appear to be exported.

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  • .NET: will Random.Random operate differently inside a static method

    - by Craig Johnston
    I am having difficulty with the following code which is inside a static method of a non-static class. int iRand; int rand; rand = new Random((int)DateTime.Now.Ticks); iRand = rand.Next(50000); The iRand number, along with some other values, are being inserted into a new row of an Access MDB table via OLEDB. The iRand number is being inserted into a field that is part of the primary key, and the insert attempt is throwing the following exception even though the iRand number is supposed to be random: System.Data.OleDb.OleDbException: The changes you requested to the table were not successful because they would create duplicate values in the index, primary key, or relationship. Change the data in the field or fields that contain duplicate data, remove the index, or redefine the index to permit duplicate entries and try again. Could the fact the method is static be making the iRand number stay the same, for some reason?

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