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  • Problems with classes (super new)

    - by user260036
    Hi, I've problems to figure it out what's happening in the following exercise, I'm learning Smalltalk, so I'm newbie. Class Anew ^super new initialize. Ainitialize a:=0. Class Bnew: aParameter |instance| instance := super new. instance b: instance a + aParameter. ^instance Binitialize b:=0. The problem says what happen when the following code is executed: B new:10. But I can't not figure it out why instance variable does not belong to A class. Thanks

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  • Get current value in a set of CSS classes using Jquery

    - by Thang Nguyen
    Dear all I have some class like this <div class = "student"> <div class = "name">Adam </div> <input class = "paperTaken"> </div> <div class = "student"> <div class = "name">Smith</div> <input class = "paperTaken"> </div> When I put the cusor on an input field (say, "paperTaken" in the first "student" class), I can get the corresponding value in class "name" (eg: Adam). Could you help me? Thank you in advance.

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  • Binding type variables that only occur in assertions

    - by Giuseppe Maggiore
    Hi! I find it extremely difficult to describe my problem, so here goes nothing: I have a bunch of assertions on the type of a function. These assertions rely on a type variable that is not used for any parameter of the function, but is only used for internal bindings. Whenever I use this function it does not compile because, of course, the compiler has no information from which to guess what type to bind my type variable. Here is the code: {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances, FlexibleContexts, EmptyDataDecls, ScopedTypeVariables, TypeOperators, TypeSynonymInstances #-} class C a a' where convert :: a -> a' class F a b where apply :: a -> b class S s a where select :: s -> a data CInt = CInt Int instance S (Int,String) Int where select (i,_) = i instance F Int CInt where apply = CInt f :: forall s a b . (S s a, F a b) => s -> b f s = let v = select s :: a y = apply v :: b in y x :: Int x = f (10,"Pippo") And here is the generated error: FunctorsProblems.hs:21:4: No instances for (F a Int, S (t, [Char]) a) arising from a use of `f' at FunctorsProblems.hs:21:4-17 Possible fix: add an instance declaration for (F a Int, S (t, [Char]) a) In the expression: f (10, "Pippo") In the definition of `x': x = f (10, "Pippo") Failed, modules loaded: none. Prelude>

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  • C# OOP File Structure?

    - by Soo
    Hey SO, I just started programming with objects recently and am trying to learn good habits early on. The way I plan to structure my application is to have two files: 1: Program.cs - This file will contain the main logic for the application 2: Class.cs - This file will contain all of the class definitions Pretty simple. What I'm wondering if I should have any more files for ... well, you tell me. Any help would be appreciated.

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  • Declare module name of classes for logging

    - by Space_C0wb0y
    I currently am adding some features to our logging-library. One of these is the possibility to declare a module-name for a class that automatically gets preprended to any log-messages writing from within that class. However, if no module-name is provided, nothing is prepended. Currently I am using a trait-class that has a static function that returns the name. template< class T > struct ModuleNameTrait { static std::string Value() { return ""; } }; template< > struct ModuleNameTrait< Foo > { static std::string Value() { return "Foo"; } }; This class can be defined using a helper-macro. The drawback is, that the module-name has to be declared outside of the class. I would like this to be possible within the class. Also, I want to be able to remove all logging-code using a preprocessor directive. I know that using SFINAE one can check if a template argument has a certain member, but since other people, that are not as friendly with templates as I am, will have to maintain the code, I am looking for a much simpler solution. If there is none, I will stick with the traits approach. Thanks in advance!

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  • WCF error service error message with shared classes

    - by sevenalive
    Source code: http://code.google.com/p/sevenupdate/source/browse/#hg/Source/SevenUpdate.Base SevenUpdate.Base.Sui cannot be used since it does not match imported DataContract. Need to exclude this type from referenced types. Now I tried unchecking reuse reference types and I was able to get my project to compile. but when sending a collection from the client it was never received or couldn't be deserialized on the server end. I really need this to work. Any help would be appreciated, the fullsource code is provided by google code.

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  • Which Qt classes use the disk directly?

    - by Jurily
    I'm trying to write a library to separate all the disk activity out into its own thread, but the documentation doesn't really care about such things. What I want to accomplish is that aside from startup, all disk activity is asynchronous, and for that, I need to wrap every class that accesses the disk. Here's what I found so far: QtCore: QFile QTemporaryFile QDir QFileInfo QFileSystemWatcher QDirIterator QSettings QtGui: QFileDialog QFileSystemModel QDirModel (unsure) QFont (unsure) QFontDialog I'm sure there are more.

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  • Injecting Dependencies into Domain Model classes with Nhibernate (ASP.NET MVC + IOC)

    - by Sunday Ironfoot
    I'm building an ASP.NET MVC application that uses a DDD (Domain Driven Design) approach with database access handled by NHibernate. I have domain model class (Administrator) that I want to inject a dependency into via an IOC Container such as Castle Windsor, something like this: public class Administrator { public virtual int Id { get; set; } //.. snip ..// public virtual string HashedPassword { get; protected set; } public void SetPassword(string plainTextPassword) { IHashingService hasher = IocContainer.Resolve<IHashingService>(); this.HashedPassword = hasher.Hash(plainTextPassword); } } I basically want to inject IHashingService for the SetPassword method without calling the IOC Container directly (because this is suppose to be an IOC Anti-pattern). But I'm not sure how to go about doing it. My Administrator object either gets instantiated via new Administrator(); or it gets loaded via NHibernate, so how would I inject the IHashingService into the Administrator class? On second thoughts, am I going about this the right way? I was hoping to avoid having my codebase littered with... currentAdmin.Password = HashUtils.Hash(password, Algorithm.Sha512); ...and instead get the domain model itself to take care of hashing and neatly encapsulate it away. I can envisage another developer accidently choosing the wrong algorithm and having some passwords as Sha512, and some as MD5, some with one salt, and some with a different salt etc. etc. Instead if developers are writing... currentAdmin.SetPassword(password); ...then that would hide those details away and take care of those problems listed above would it not?

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  • How do you drop in substitute JRE classes?

    - by evilfred
    Hi, java.util.zip has well-known problems with native memory usage, so i'm trying to use a drop-in replacement called "jazzlib". unfortunately as is typical for sourceforge projects there is no documentation. If I add the jar to my classpath then Java freaks out and gives me "prohibited package name" errors because it replaced java.util.zip. How do I tell Java that this is what I want it to do?

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  • How does java implement inner class closures?

    - by thecoop
    In Java an anonymous inner class can refer to variables in it's local scope: public class A { public void method() { final int i = 0; doStuff(new Action() { public void doAction() { Console.printf(i); // or whatever } }); } } My question is how is this actually implemented? How does i get to the anonymous inner doAction implementation, and why does it have to be final?

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  • Reuse classes in an id based css

    - by C. Ross
    I have a id based CSS file where I noticed I'm mostly repeating myself. What I'd like to do is specify that an item with an id follows a certain class + some other rules. For example: I'd like id id1 to have all the properties of class LinkButton applied as well as the value back-color: green. Is there a way to do this in the css file? Is there a better way to do what I'm looking at?

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  • Limited options for accessing events in derived classes?

    - by maxp
    Im refactoring a class, and moving sections into a base class. I have a few events similar to public event EventHandler GridBinding; Which are now in the base class, but i am finding i cannot now check to see if the event is null in my derived class. Doing so gives me the error: The event 'xyz.GridBinding' can only appear on the left hand side of += or -= (except when used from within the type 'xyz._MyBaseClass'). Is this correct, am i missing anything, or is there any way to get around this or is writing an accessor the only way to do this? I am using c#/.net 4.0

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  • Message queue proxy in Python + Twisted

    - by gasper_k
    Hi, I want to implement a lightweight Message Queue proxy. It's job is to receive messages from a web application (PHP) and send them to the Message Queue server asynchronously. The reason for this proxy is that the MQ isn't always avaliable and is sometimes lagging, or even down, but I want to make sure the messages are delivered, and the web application returns immediately. So, PHP would send the message to the MQ proxy running on the same host. That proxy would save the messages to SQLite for persistence, in case of crashes. At the same time it would send the messages from SQLite to the MQ in batches when the connection is available, and delete them from SQLite. Now, the way I understand, there are these components in this service: message listener (listens to the messages from PHP and writes them to a Incoming Queue) DB flusher (reads messages from the Incoming Queue and saves them to a database; due to SQLite single-threadedness) MQ connection handler (keeps the connection to the MQ server online by reconnecting) message sender (collects messages from SQlite db and sends them to the MQ server, then removes them from db) I was thinking of using Twisted for #1 (TCPServer), but I'm having problem with integrating it with other points, which aren't event-driven. Intuition tells me that each of these points should be running in a separate thread, because all are IO-bound and independent of each other, but I could easily put them in a single thread. Even though, I couldn't find any good and clear (to me) examples on how to implement this worker thread aside of Twisted's main loop. The example I've started with is the chatserver.py, which uses service.Application and internet.TCPServer objects. If I start my own thread prior to creating TCPServer service, it runs a few times, but the it stops and never runs again. I'm not sure, why this is happening, but it's probably because I don't use threads with Twisted correctly. Any suggestions on how to implement a separate worker thread and keep Twisted? Do you have any alternative architectures in mind?

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  • Best practise for overriding static classes

    - by maxp
    As it is not possible to override a static class in c#, if i want to override a method I generally define a delegate matching the signature of the static method, then modify the method along the lines of: public static void foo(int bar) { if (delegatename!=null) { delegatename.Invoke(bar); } else { //execute previous code as normal } } I feel a twinge of guilt, knowing this is a bit messy. Can anyone suggest a neater solution to this problem (other than rewriting the original structure)

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  • Forward declaration of derived inner class

    - by Loom
    I ran into problem implementing some variations of factory method. // from IFoo.h struct IFoo { struct IBar { virtual ~IBar() = 0; virtual void someMethod() = 0; }; virtual IBar *createBar() = 0; }; // from Foo.h struct Foo : IFoo { // implementation of Foo, Bar in Foo.cpp struct Bar : IBar { virtual ~Bar(); virtual void someMethod(); }; virtual Bar *createBar(); // implemented in Foo.cpp }; I'd like to place declaration of Foo::Bar in Foo.cpp. For now I cannot succeed: struct Foo : IFoo { //struct Bar; //1. error: invalid covariant return type // for ‘virtual Foo::Bar* //struct Bar : IBar; //2. error: expected ‘{’ before ‘;’ token virtual Bar *createBar(); // virtual IBar *createBar(); // Is not acceptable by-design }; Is there a trick to have just forward declaration of Boo in Foo.hpp and to have full declaration in Foo.cpp?

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  • Codeigniter how to access class variables

    - by Obay
    I thought this was going to be a no-brainer but I can't seem to access member variables: class MyObject extends Controller { private $START_OF_WEEK = 1; /* constructor here */ function index() { echo $this->$START_OF_WEEK; } } echo $this->$START_OF_WEEK; says Cannot access empty property How do I access member variables? Or... how do I declare them correctly?

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  • Specializing a class template constructor

    - by SilverSun
    I'm messing around with template specialization and I ran into a problem with trying to specialize the constructor based on what policy is used. Here is the code I am trying to get to work. #include <cstdlib> #include <ctime> class DiePolicies { public: class RollOnConstruction { }; class CallMethod { }; }; #include <boost/static_assert.hpp> #include <boost/type_traits/is_same.hpp> template<unsigned sides = 6, typename RollPolicy = DiePolicies::RollOnConstruction> class Die { // policy type check BOOST_STATIC_ASSERT(( boost::is_same<RollPolicy, DiePolicies::RollOnConstruction>::value || boost::is_same<RollPolicy, DiePolicies::CallMethod>::value )); unsigned m_die; unsigned random() { return rand() % sides; } public: Die(); void roll() { m_die = random(); } operator unsigned () { return m_die + 1; } }; template<unsigned sides> Die<sides, DiePolicies::RollOnConstruction>::Die() : m_die(random()) { } template<unsigned sides> Die<sides, DiePolicies::CallMethod>::Die() : m_die(0) { } ...\main.cpp(29): error C3860: template argument list following class template name must list parameters in the order used in template parameter list ...\main.cpp(29): error C2976: 'Die' : too few template arguments ...\main.cpp(31): error C3860: template argument list following class template name must list parameters in the order used in template parameter list Those are the errors I get in Microsoft Visual Studio 2010. I'm thinking either I can't figure out the right syntax for the specialization, or maybe it isn't possible to do it this way.

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  • Help creating custom iPhone Classes

    - by seanny94
    This should be a simple question, but I just can't seem to figure it out. I'm trying to create my own class which will provide a simpler way of playing short sounds using the AudioToolbox framework as provided by Apple. When I import these files into my project and attempt to utilize them, they just don't seem to work. I was hoping someone would shed some light on what I may be doing wrong here. simplesound.h #import <Foundation/Foundation.h> @interface simplesound : NSObject { IBOutlet UILabel *statusLabel; } @property(nonatomic, retain) UILabel *statusLabel; - (void)playSimple:(NSString *)url; @end simplesound.m #import "simplesound.h" @implementation simplesound @synthesize statusLabel; - (void)playSimple:(NSString *)url { if (url = @"vibrate") { AudioServicesPlaySystemSound(kSystemSoundID_Vibrate); statusLabel.text = @"VIBRATED!"; } else { NSString *paths = [[NSBundle mainBundle] resourcePath]; NSString *audioF1ile = [paths stringByAppendingPathComponent:url]; NSURL *audioURL = [NSURL fileURLWithPath:audioFile isDirectory:NO]; SystemSoundID mySSID; OSStatus error = AudioServicesCreateSystemSoundID ((CFURLRef)audioURL,&mySSID); AudioServicesAddSystemSoundCompletion(mySSID,NULL,NULL,simpleSoundDone,NULL); if (error) { statusLabel.text = [NSString stringWithFormat:@"Error: %d",error]; } else { AudioServicesPlaySystemSound(mySSID); } } static void simpleSoundDone (SystemSoundID mySSID, void *args) { AudioServicesDisposeSystemSoundID (mySSID); } } - (void)dealloc { [url release]; } @end Does anyone see what I'm trying to accomplish here? Does anyone know how to remedy this code that is supposedly wrong?

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  • Change classes instantiated with loadNibNamed

    - by Nick H247
    I am trying to change the class of objects created with a nib with the iPhone SDK. The reason for this is; i dont know until runtime what the class is that i want the nib object to be (though they will have the same UIView based super class), and i dont want to create a different nib for every eventuality - as the .nib will be the same for each, apart from the class of one object. I have been successful, with a couple of methods, but either have some knock on effects or am unsure of how safe the methods I have used are: Method 1: Override alloc, on the super class and set a c variable to the class I require: + (id) alloc { if (theClassIWant) { id object = [theClassIWant allocWithZone:NSDefaultMallocZone()]; theClassIWant = nil; return object; } return [BaseClass allocWithZone:NSDefaultMallocZone()]; } this works well, and i assume is 'reasonably' safe, though if I alloc a subclass myself (without setting 'theClassIWant') - an object of the base class is created. I also dont really like the idea of overriding alloc... Method 2: use object_setClass(self,theClassIWant) in initWithCoder (before calling initWithCoder on the super class): - (id) initWithCoder:(NSCoder *)aDecoder { if (theClassIWant) { // the framework doesn't like this: //[self release]; //self = [theClassIWant alloc]; // whoa now! object_setClass(self,theClassIWant); theClassIWant = nil; return [self initWithCoder:aDecoder]; } if (self = [super initWithCoder:aDecoder]) { ... this also works well, but not all the subclasses are necessarily going to be the same size as the super class, so this could be very unsafe! To combat this i tried releasing and re-allocing to the correct type within initWithCoder, but i got the following error from the framework: "This coder requires that replaced objects be returned from initWithCoder:" dont quite get what this means! i am replacing an object in initWithCoder... Any comments on the validity of these methods, or suggestions of improvements or alternatives welcome!

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  • Why am I having this InstantiationException in Java when accessing final local variables?

    - by Oscar Reyes
    I was playing with some code to make a "closure like" construct ( not working btw ) Everything looked fine but when I tried to access a final local variable in the code, the exception InstantiationException is thrown. If I remove the access to the local variable either by removing it altogether or by making it class attribute instead, no exception happens. The doc says: InstantiationException Thrown when an application tries to create an instance of a class using the newInstance method in class Class, but the specified class object cannot be instantiated. The instantiation can fail for a variety of reasons including but not limited to: - the class object represents an abstract class, an interface, an array class, a primitive type, or void - the class has no nullary constructor What other reason could have caused this problem? Here's the code. comment/uncomment the class attribute / local variable to see the effect (lines:5 and 10 ). import javax.swing.*; import java.awt.event.*; import java.awt.*; class InstantiationExceptionDemo { //static JTextField field = new JTextField();// works if uncommented public static void main( String [] args ) { JFrame frame = new JFrame(); JButton button = new JButton("Click"); final JTextField field = new JTextField();// fails if uncommented button.addActionListener( new _(){{ System.out.println("click " + field.getText()); }}); frame.add( field ); frame.add( button, BorderLayout.SOUTH ); frame.pack();frame.setVisible( true ); } } class _ implements ActionListener { public void actionPerformed( ActionEvent e ){ try { this.getClass().newInstance(); } catch( InstantiationException ie ){ throw new RuntimeException( ie ); } catch( IllegalAccessException ie ){ throw new RuntimeException( ie ); } } } Is this a bug in Java? edit Oh, I forgot, the stacktrace ( when thrown ) is: Caused by: java.lang.InstantiationException: InstantiationExceptionDemo$1 at java.lang.Class.newInstance0(Class.java:340) at java.lang.Class.newInstance(Class.java:308) at _.actionPerformed(InstantiationExceptionDemo.java:25)

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  • Lua class instance with nested tables

    - by Anonnobody
    Hello, Simple lua game with simple class like so: creature = class({ name = "MONSTER BADDY!", stats = { power = 10, agility = 10, endurance = 10, filters = {} }, other_things = ... }) creatureA = creature.new() creatureB = creature.new() creatureA.name = "Frank" creatureB.name = "Zappa" creatureA.stats.agility = 20 creatureB.stats.power = 12 -- blah blah blah Non table values are individual to each instance, but table values are shared among all instances and if I modify a stats.X value in one instance, all other instances see the same stats table. Q1: Is my OO implementation flawed? I tried LOOP and the same result occured, is there a fundamental flaw in my logic? Q2: How would you have each instance of creature have it's own stats table (and sub tables)? PS. I cannot flatten my class table as it's a bit more complicated than the example and other parts of the code are simplified with this nested table implementation. Thanks a bunch.

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  • Basic Question on storing variables c# for use in other classes

    - by Calibre2010
    Ok guys I basically have a class which takes in 3 strings through the parameter of one of its method signatures. I've then tried to map these 3 strings to global variables as a way to store them. However, when I try to call these global variables from another class after instantiating this class they display as null values. this is the class which gets the 3 strings through the method setDate, and the mapping.. public class DateLogic { public string year1; public string month1; public string day1; public DateLogic() { } public void setDate(string year, string month, string day) { year1 = year; month1 = month; day1 = day; // getDate(); } public string getDate() { return year1 + " " + month1 + " " + day1; } } After this I try call this class from here public static string TimeLine2(this HtmlHelper helper, string myString2) { DateLogic g = new DateLogic(); string sday = g.day1; string smonth = g.month1; string syr = g.year1; } I've been debugging and the values make it all the way to the global variables but when called from this class here it doesnt show them, just shows null. Is this cause I'm creating a brand new instance, how do i resolve this?

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  • .NET Framework - Possible memory-leaky classes?

    - by Robert Fraser
    Just the other day I was investigating a memory leak that was ballooning the app from ~50MB to ~130MB in under two minutes. Turns out that the problem was with the ConcurrentQueue class. Internally, the class stores a linked list of arrays. When an item is dequeued from the ConcurrentQueue, the index in the array is bumped, but the item remains in the array (i.e. it's not set to null). The entire array node is dropped after enough enqueues/dequeues, so it's not technically a leak, but if storing only a few large objects in the ConcurrentQueue, this can get out of hand fast. The documentation makes no note of this danger. I was wondering what other potential memory pitfalls are in the Base Class Library? I know about the Substring one (that is, if you call substring and just hold onto the result, the whole string will still be in memory). Any others you've encountered?

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