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• Questions about "casting operation" in OOP

  - by rhapsodyn

  When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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• Which Java library lets me initialize an object's properties from a properties file?

  - by Kjetil Ødegaard

  Is there a Java library that lets you "deserialize" a properties file directly into an object instance? Example: say you have a file called init.properties: username=fisk password=frosk and a Java class with some properties: class Connection { private String username; private String password; public void setUsername(String username) { this.username = username; } public void setPassword(String password) { this.password = password; } } I want to do this: Connection c = MagicConfigurator.configure("init.properties", new Connection()) and have MagicConfigurator apply all the values from the properties file to the Connection instance. Is there a library with a class like this?

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• Using locks inside a loop

  - by Xaqron

  // Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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• Python design mistakes

  - by Andrea

  A while ago, when I was learning Javascript, I studied Javascript: the good parts, and I particularly enjoyed the chapters on the bad and the ugly parts. Of course, I did not agree with everything, as summing up the design defects of a programming language is to a certain extent subjective - although, for instance, I guess everyone would agree that the keyword with was a mistake in Javascript. Nevertheless, I find it useful to read such reviews: even if one does not agree, there is a lot to learn. Is there a blog entry or some book describing design mistakes for Python? For instance I guess some people would count the lack of tail call optimization a mistake; there may be other issues (or non-issues) which are worth learning about.

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• to write log files in two different files

  - by Sun

  my application run on customized client framework,the client framework used log4net to log their own log files. we are(our application) has to use the same log4net to log our log files in our own path(say our customized path). currently the our log files are created but log are not writing in that file.it is writting in the client framework log file. searched lot of sites the link http://stackoverflow.com/questions/308436/log4net-programmatcially-specify-multiple-loggers-with-multiple-file-appenders helped me to configure the log4net config programatically, still im log statemets are not written in my log file.the code used as below public class TraceLog { private string message = string.Empty; private static ILog ILogger = null; private static TraceLog instance = new TraceLog(); private TraceLog() { SetLevel("Log4net.MainForm", "ALL"); AddAppender("Log4net.MainForm", CreateFileAppender("FileAppender", "C:\\mylog.log")); } public static TraceLog Instance { get { return instance; } } public void Debug(string logMessage) { message = PrepareLog(logMessage); ILogger.Debug(message); } protected string PrepareLog(string logMessage) { string message = GetFileMethodLineNumberInfo(); message += logMessage; return message; } protected string GetFileMethodLineNumberInfo() { StackTrace stackTrace = new StackTrace(true); // The position 3 is relative to the index of the specified method StackFrame stackFrame = stackTrace.GetFrame(3); return (stackFrame.GetMethod().DeclaringType.Name + "/" + stackFrame.GetMethod().Name + "/" + stackFrame.GetFileLineNumber() + ":"); } private static void SetLevel(string loggerName, string levelName) { ILogger = LogManager.GetLogger(loggerName); log4net.Repository.Hierarchy.Logger l = (log4net.Repository.Hierarchy.Logger)ILogger.Logger; l.Level = l.Hierarchy.LevelMap[levelName]; } private static void AddAppender(string loggerName, IAppender appender) { ILogger = LogManager.GetLogger(loggerName); log4net.Repository.Hierarchy.Logger l = (log4net.Repository.Hierarchy.Logger)ILogger.Logger; l.AddAppender(appender); } private static IAppender CreateFileAppender(string name, string fileName) { FileAppender appender = new FileAppender(); appender.Name = name; appender.File = fileName; appender.AppendToFile = true; //PatternLayout layout = new PatternLayout(); //layout.ConversionPattern = "%d [%t] %-5p %c [%x] - %m%n"; //layout.ActivateOptions(); //appender.Layout = layout; appender.ActivateOptions(); return appender; } } } anyone pls help how to solve this

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• Log Shipped but Won't Update

  - by MooCow

  I'm currently taking the MS SQL 2K5 Admin course at a local college and ran into a problem with the Log Shipping part. My setup is the following: Windows 7 x64 SQL 2005 SP3 2 SQL server instances on the same machine Log Shipping settings: Performed full then log back up of Primary Manually restore on Secondary in STANDBY MODE Insert a new record into the table Set up Log Shipping on Primary using SQL Authenication login to connect to the Secondary Set up timers and copy destination on Secondary Monitoring instance not being used I set up a shared folder for WORKGROUP so both instances on the machine can read & write to it. I can see transaction logs generated and copied as defined by the Transaction Shipping wizard. However, the specified table on the Secondary instance is not updating.

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• navigationproblem

  - by sudhakarilla

  I have problem .. i get debugerror i will used in json Category *selectcategory = [[data categorys]objectAtindex:indexPath.row]; productlistviewcontroller *plviewcontroller = [[productlistviewcontroller alloc]initwithNibName:@"productlistviewcontroller" bundle:nil]; plviewcontroller.category = selectedcategory; [self.navigationcontroller pushviewcontroller:plviewcontroller animated:YES]; please check the my program. it doesnot goto nextviewcontroller. console error is 2009-02-13 18:32:17.405 xxxxxxxx[1491:20b] * -[NsDecimalNumber length]: unrecognized selector sent to instance 0xc3f10ff0 2009-02-13 18:32:17.406 xxxxxxxx[1491:20b] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '** -[NsDecimalNumber length ]: unrecognized selector sent to instance 0xc3f10ff0' 2009-02-13 18:32:17.406 xxxxxxxx[1491:20b] Stack: ( 2417225995, 2527100475, 2417255178, 2417248524, 2417248722, 22199, 9853, 816111650, 816149355, 2458333742, 2416728869, 2416729304, 827745792, 827745989, 816114848, 816160924, 9628, 9482 ) please send soluation...

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• Prevent Erroneous Property Assignment

  - by Gordon

  Porting android applications to iphone applications always gives me the following pattern that I accidentally create: - (void) myFunc:(id)prop { self.property = property; } Which instead should be: - (void) myFunc:(id)prop { self.property = prop; } This always causes my program to quietly break because property gets reset to its existing value rather than being set to the new value, 'prop'. I cannot name the parameter 'prop' to 'property' since the compile complains that the parameter masks the instance variables visibility. Is there a good way to avoid this situation? There are no compiler warnings. Is there a way to make xcode prevent this? I cannot see very many situations where you would set a property to the value of its underlying instance variable (maybe to trigger a KVO binding?), but I don't see myself doing that in majority of cases. I understand the above code is synthetic and should be done with @synthesize, but I am just using it as a simplified example to illustrate my point.

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• C++ Singleton design pattern

  - by Artem Barger

  Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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• Deleting N lines from every start point

  - by syker

  How would I delete the 6 lines starting from every instance of a word i see?

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• Strange pattern matching with functions instancing Show

  - by Sean D

  So I'm writing a program which returns a procedure for some given arithmetic problem, so I wanted to instance a couple of functions to Show so that I can print the same expression I evaluate when I test. The trouble is that the given code matches (-) to the first line when it should fall to the second. {-# OPTIONS_GHC -XFlexibleInstances #-} instance Show (t -> t-> t) where show (+) = "plus" show (-) = "minus" main = print [(+),(-)] returns [plus,plus] Am I just committing a motal sin printing functions in the first place or is there some way I can get it to match properly? edit:I realise I am getting the following warning: Warning: Pattern match(es) are overlapped In the definition of `show': show - = ... I still don't know why it overlaps, or how to stop it.

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• Exceptions confusion

  - by Misiur

  Hi there. I'm trying to build site using OOP in PHP. Everyone is talking about Singleton, hermetization, MVC, and using exceptions. So I've tried to do it like this: Class building whole site: class Core { public $is_core; public $theme; private $db; public $language; private $info; static private $instance; public function __construct($lang = 'eng', $theme = 'default') { if(!self::$instance) { try { $this->db = new sdb(DB_TYPE.':host='.DB_HOST.';dbname='.DB_NAME, DB_USER, DB_PASS); } catch(PDOException $e) { throw new CoreException($e->getMessage()); } try { $this->language = new Language($lang); } catch(LangException $e) { throw new CoreException($e->getMessage()); } try { $this->theme = new Theme($theme); } catch(ThemeException $e) { throw new CoreException($e->getMessage()); } } return self::$instance; } public function getSite($what) { return $this->language->getLang(); } private function __clone() { } } Class managing themes class Theme { private $theme; public function __construct($name = 'default') { if(!is_dir("themes/$name")) { throw new ThemeException("Unable to load theme $name"); } else { $this->theme = $name; } } public function getTheme() { return $this->theme; } public function display($part) { if(!is_file("themes/$this->theme/$part.php")) { throw new ThemeException("Unable to load theme part: themes/$this->theme/$part.php"); } else { return 'So far so good'; } } } And usage: error_reporting(E_ALL); require_once('config.php'); require_once('functions.php'); try { $core = new Core(); } catch(CoreException $e) { echo 'Core Exception: '.$e->getMessage(); } echo $core->theme->getTheme(); echo "<br />"; echo $core->language->getLang(); try { $core->theme->display('footer'); } catch(ThemeException $e) { echo $e->getMessage(); } I don't like those exception handlers - i don't want to catch them like some pokemons... I want to use things simple: $core-theme-display('footer'); And if something is wrong, and debug mode is enabled, then aplication show error. What should i do?

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• iPhone developing FOR jailbroken devices (not USING jailbroken devices!)

  - by Marek

  I would like to dig into developing for jailbroken devices, just to test what the device could do. I would like, for instance, to alter the ipod music based on geo-location, so i have to program a new daemon that runs in background and fetch gps informations at regular interlavs and then make something with them. Longitude, longitude, for instance, does exactly this, even when the device is locked, and then upload the informations on google latidude. I have some experience as an iphone developer, but i'm not sure on where to find documentation to accomplish such a task. I know about the books "iphone open application development" and "the iphone developer's coockbook", but i don't own them and i'm not sure they have what i'm looking for. Any advice on this?

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• Globally overrride MonthNames for all instances of a specific culture

  - by Pauli Østerø

  So, i have this problem where Microsoft actually got the month names wrong for the Greenlandic culture (kl-GL). I also know that i can pass my own array of string to the DateTimeFormatInfo.MonthNames Property, but it seems like the values i specify is only used in the scope of that one CultureInfo instance. Is there a way to tell .Net that every time i have an instance of the kl-GL culture these specific monthnames should be used? I know that you can create user specific cultures, but i don't have access to some legacy code to actually change the code to use a my own userspecified culture.

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• Can Fluent NHibernate be configured to use an arbitrary prefix on a property backing field?

  - by dommer

  I'm currently using a convention to (auto)map collection properties to backing fields in Fluent NHibernate. So, I map a property "Orders" to a field "_orders". The convention I'm using to do this is: public class HasManyAccessConvention : IHasManyConvention { public void Apply(IOneToManyCollectionInstance instance) { instance.Access.CamelCaseField(CamelCasePrefix.Underscore); } } Can I write a convention that maps a (collection) property to a field with a non-standard prefix (ignoring whether this is good coding practice for the present)? So, the property "Orders" would be mapped to "xyz_orders", for example. If so, how would I go about this?

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• How to work with overlapping repositories in Mercurial

  - by Paul W Homer

  Often I want to have a main repository of source, shared by several "similar" projects. Each sub-project contains most of the same files, but is a specific configurable instance. That means there are usually a bunch of files and directories that need to be different for each instance. In CVS I used to create the main repository and the secondary ones, then use the modules file to bind the two together for a specific name. In SVN I used svn:externals to tie back the secondary directories into the main one. What works in Mercurial?

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• Type hinting and optional attributes in PHP

  - by Álvaro G. Vicario

  I have a class method that deals with dates: public function setAvailability(DateTime $start, DateTime $end){ } Since item availability can have lower limit, upper limit, both or none, I'd like to make setAvailability() accept NULL values as well. However, the NULL constant violates the type hinting: $foo->setAvailability(NULL, $end); triggers: Catchable fatal error: Argument 1 passed to Foo::setAvailability() must be an instance of DateTime, null given And, as far as I know, I cannot have a DateTime instance with no value. (Can I?) For a reason I cannot grasp, this seems to work: public function setAvailability(DateTime $start=NULL, DateTime $end=NULL){ } ... $foo->setAvailability(NULL, $end); But it looks like a hack that works by pure chance. How would you deal with unset dates in PHP classes?

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• Windsor + NHibernate + ISession + MVC

  - by dbones

  Hi I am trying to get Windsor to give me an instance ISession for each request, which should be injected into all the repositories Here is my container setup container.AddFacility<FactorySupportFacility>().Register( Component.For<ISessionFactory>().Instance(NHibernateHelper.GetSessionFactory()).LifeStyle.Singleton, Component.For<ISession>().LifeStyle.Transient .UsingFactoryMethod(kernel => kernel.Resolve<ISessionFactory>().OpenSession()) ); //add to the container container.Register( Component.For<IActionInvoker>().ImplementedBy<WindsorActionInvoker>(), Component.For(typeof(IRepository<>)).ImplementedBy(typeof(NHibernateRepository<>)) ); Its based upon a StructureMap post here http://www.kevinwilliampang.com/2010/04/06/setting-up-asp-net-mvc-with-fluent-nhibernate-and-structuremap/ however, when this is run, a new Session is created for every object it is injected too. what am I missing? thanks in advanced (FYI the NHibernateHelper, sets up the config for Nhib)

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• C# Why does this code not show a GUI properly?

  - by Tom

  class Program { static String ChannelName = null; static Form1 f; static void Main() { f = new Form1(); f.Show(); try { MY CODE WHICH CALLS INTO ANOTHER CLASS BUT CANNOT PASS THE GUI INSTANCE AS IT USES REMOTING } } } I know this isnt the best/normal way to do it, but i need to write data to the GUI from a class which has bo instance of the GUI so i was going to call Program.method() and use a function to write to the GUI in program. However when i run the above my GUI displays but with the windows hourglass? Could someone show me a quick fix so that i can still crudely show the GUI, let the application code run and then later write to the GUI?

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• Reference variable to an object instantiated/initialized in another class in Java

  - by Alex

  The reason I'm asking is because I'm getting NullPointerException. I now this is very easy but I'm pretty new programming and find this a bit confusing. So say I have initialized an object in a class and want to access that same object from another class. Like now for instance I'm working on a small Chess game, in my model Game class I have an instance of Board, an object. Board, in turn, has an array of Squares. Square[][]. Game has board, board has Square[][]. Now if I want to access the Square[][] through the object board (in Game) of type Board. Do I just declare a variable with the same name and type or do I have to initialize it again? Board board OR Board board = new Board(); Note, I have already initialized board in the class Game so if I do it again, won't they be two totally different Board objects?

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• Does every browser open a new HTTPSession

  - by user496934

  I am working on a webbased application which has JSP and servlets. In my application, I am binding some objects to sessions like the following code -- HttpSession session = p_req.getSession(); session.setAttribute(DOWNLOAD_With_WARNINGS, downloadMap); Later I am retrieving them using session.getAttribute. I would like to know if every time I open a new browser does it open a new HTTP session. Because , if I do a setAttribute with some value in one browser instance, that change is visible when I do a getAttribute using the other browser instance.

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• UITableView: How to display more then one detail cell and own custom button

  - by Jacob

  For instance [Course Name (cell title) [Value: 30% (cell.detailTextLabel) [my own custom button here as selector] [Due: April, 2,2010](How can i add this)

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• Running script constantly in background: daemon, lock file with crontab, or simply loop?

  - by Mauritz Hansen

  I have a Perl script that queries a database for a list of files to process processes the files and then exits Upon startup this script creates a file (let's say script.lock), and upon exit it removes this file. I have a crontab entry that runs this script every minute. If the lockfile exists then the script exits, assuming that another instance of itself is running. The above process works fine but I am not very happy with the robustness of this approach. Specifically, if for some reason the script exits prematurely and the lockfile is not removed then a new instance will not execute properly. I would appreciate some advice on the following: Is using the lock file a good approach or is there a better/more robust way to do this? Is using crontab for this a good idea or could I better write an endless loop with sleep()? Should I use the GNU 'daemon' program or the Perl Proc::Daemon module (or some other equivalent) for this?

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• NSTableview objectAtIndex error

  - by Matt S.

  I followed the guide here, but for some reason, the table view shows this in the console when I attempt to scroll through it: -[NSCFString objectAtIndex:]: unrecognized selector sent to instance 0x100227710

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• possible to show composition relationship in a diagram generated from PHP source code?

  - by ajsie

  i have tested several UML applications for whether they could show composition relationships in the UML diagrams generated form the PHP source code or not, and the result is they can't. i know that this is a typical problem for PHP cause we don't declare a data type when we code, so it's difficult for the UML applications to know if an instance variable is a reference to an object or not. i also tested nWire with the same result. will there never be applications that could show us a complete map over all object relationships more than just inheritance? i think it's a pity that you can't have a good view over all the relationships for an application. cause when i use an open source solution, i always want to know how the objects are related to each other. maybe we could make comments for the instance variable telling the software that this is an reference to an object? but that would mean that the mapping software is using this solution. i feel its a pity nWire/visual paradigm can't give us a complete map:(

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