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  • Example of contravariance

    - by Misha
    I am thinking of the following example to illustrate why contravariance is useful. Let's consider a GUI framework with Widgets, Events, and Event Listeners. abstract class Event; class KeyEvent extends Event class MouseEvent extends Event trait EventListener[-Event] { def listen(e:Event) } Let Widgets define the following methods: def addKeyEventListener(listener:EventListener[KeyEvent]) def addMouseEventListener(listener:EventListener[MouseEvent]) These methods accept only "specific" event listeners, which is fine. However I would like to define also "kitchen-sink" listeners, which listen to all events, and pass such listeners to the "add listener" methods above. For instance, I would like to define LogEventListener to log all incoming events class LogEventListener extends EventListener[Event] { def listen(e:Event) { log(event) } } Since the trait EventListener is contravariant in Event we can pass LogEventListener to all those "add listener" methods without losing their type safety. Does it make sense ?

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  • Inheriting database connection in PHP OOP

    - by vrode
    My abstract class Database is made for database interaction and any child of this class (UserDatabase, ActionDatabase, EventDatabase) inherits its database connection which is defined as static. `abstract class Database { static $connection = mysql_connect( ); } class UserDatabase extends Database { ... public function __construct( ) { $connection ? "connected" : "not connected"; $this-table = "users"; mysql_query( "FROM " . $this-table . " SELECT *" ); } } ` Does that mean, that my database connection is only set up and stored in memory once and passed on to subclasses as reference without being replicated for each instance? Is this how you would implement you OOP-correct database interface?

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  • How can I find the names of AD Group policies that a user/pc is using?

    - by Russ
    I am having trouble locating some settings in group policy so I can make changes due to the convoluted nature of our policies. What I would like to be able to do is go to a specific PC and see what group policies are being applied, so I can focus on those policies. My goal would be to clean up the GP's a bit, while allowing me to "walk the tree" to see what people have implemented and what is worthless. Thanks. EDIT: In this specific case, I am looking to find which GP maped drives are configured in. (User Configuration -- Preferences -- Windows Settings -- Drive Maps)

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  • Rails architecture questions

    - by justinbach
    I'm building a Rails site that, among other things, allows users to build their own recipe repository. Recipes are entered either manually or via a link to another site (think epicurious, cooks.com, etc). I'm writing scripts that will scrape a recipe from these sites given a link from a user, and so far (legal issues notwithstanding) that part isn't giving me any trouble. However, I'm not sure where to put the code that I'm writing for these scraper scripts. My first thought was to put it in the recipes model, but it seems a bit too involved to go there; would a library or a helper be more appropriate? Also, as I mentioned, I'm building several different scrapers for different food websites. It seems to me that the elegant way to do this would be to define an interface (or abstract base class) that determines a set of methods for constructing a recipe object given a link, but I'm not sure what the best approach would be here, either. How might I build out these OO relationships, and where should the code go?

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  • Why is the base class being called?

    - by oneBelizean
    I'm new to c# so bare with me. But here's my situation. interface Icontainer{ string name(); } abstract class fuzzyContainer : Icontainer{ string name(){ return "Fuzzy Container"; } } class specialContainer: fuzzyContainer{ string name(){ return base.name() + " Special Container"; } } Icontainer cont = new SpecialContainer(); cont.name(); // I expected "Fuzzy Container Special Container" as the output. When I run my code as described above the output is simply "Fuzzy Container". What am i missing here? Is there a better way to get the desired results?

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  • file:// command-line arguments

    - by Cory Grimster
    Is it possible to pass command-line arguments to a program that is invoked via a file:// url? I'm trying to include Remote Desktop links in a wiki page that lists some servers: <a href="file:///c|/windows/system32/mstsc.exe /v:serverName">serverName</a> When I omit the argument the link works fine, but when I include it the link doesn't work. I Googled around a bit and couldn't find any references to this. I suspect that the answer is that file:// urls simple don't accept arguments (I can think of all kinds of ways to abuse them if they do), but I thought I'd throw it out there in case I've simply got the syntax wrong. Thanks.

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  • JVM specification and Java compiler code useful for SCJP preparation ?

    - by BenoitParis
    I'm preparing the SCJP exam with the almost official study book ("SCJP Sun Certified Programmer for Java 6 Exam 310-065") I understand that Java programming is writting code that fulfills a certain high-level contract; So that Java can stay platform-independent. However, I have trouble understanding and remembering things when it comes to highly specific SCJP items (and they are numerous) The book stays high-level and does not provide examples of how one compiler would handle things. This is the same thing for runtime issues (JVM level): things are too much abstract for me. Rules often seems arbitrary and therefore, with no well defined purpose, are difficult to remember. Or maybe it's that sometimes I just don't get the underlying purpose. And here is the question: Would a JVM specification and/or some java compiler code help in preparing the SCJP? Have you had the need for such material or is the book sufficient enough? Also, please share the resources you used, apart from the book.

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  • getting Thunderbird rescan imap folder

    - by asdmin
    Since I got an external program (imapfilter) modifying my imap folder, thunderbird keeps loosing track of new messages. Messages are moved upon arrival in sub-folders, making Thunderbird unable keep tracking them - therefore I have no clue which folders to look for new messages, and newly created folders (even I subscribe them after creation) does not show up until I restart the mail client. Is there any extension or setting for Thunderbird which I could use to trigger re-scanning my folder tree? Please don't waste time on advices like restarting Thunderbird: takes a great amount of time, or "use Evolution (or any other mail client)", or use internal mail filters: they are not sophisticated enough or procmail/fetchmail: I'm arranging a remote imap server for good EXTENSION 1: even folders can be created in the background, without Thunderbird would know it has been created.

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  • Deserialising Json to derived types in Asp.Net Web API

    - by IoChaos
    I'm calling a method of my WebAPI sending a json that I would like to match (or bind) with a model. In the controller I have a method like: public Result Post([ModelBinder(typeof(CustomModelBinder))]MyClass model); 'MyClass', wich is given as a parameter is an abstract class. I would like that at, depending of the type of json passed, the correct inherited class is instantiated. To achieve it, I'm trying to implement a custom binder. The problem is that (I don't know if it's very basic but I can't find anything) I don't know how to retrieve the raw Json (or better, some kind of serialization) that comes in the request. I see: actionContext.Request.Content But all methods are exposed as async. I don't know who this fits with passing the generate model to the controller method... Thanks a lot!

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  • Scp only a specific folder

    - by Ben
    Some command line syntax I don't know how to set, am a noob sometimes, sorry is that's obvious Let's says I have the following path for all my assets : /var/www/site/system/images/{image_id}/{format}/{file}.{extension} Inside the {image_id} folder, I have multiple formats (original, medium, thumb, etc...). I only want to import the /var/www/site/system/images/{image_id}/original folder, and keep the structure locally scp -r username@server:/var/www/site/system/images/*/original ~/Site/site/system/images This one does get it all, but all the files end up in the same and unique folder, no structure. I'd like to keep the structure. Is there something to do for it ?

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  • Making OR/M loosely coupled and abstracted away from other layers.

    - by Genuine
    Hi all. In an n-tier architecture, the best place to put an object-relational mapping (OR/M) code is in the data access layer. For example, database queries and updates can be delegated to a tool like NHibernate. Yet, I'd like to keep all references to NHibernate within the data access layer and abstract dependencies away from the layers below or above it. That way, I can swap or plug in another OR/M tool (e.g. Entity Framework) or some approach (e.g. plain vanilla stored procedure calls, mock objects) without causing compile-time errors or a major overhaul of the entire application. Testability is an added bonus. Could someone please suggest a wrapper (i.e. an interface or base class) or approach that would keep OR/M loosely coupled and contained in 1 layer? Or point me to resources that would help? Thanks.

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  • Does Qt support virtual pure slots ?

    - by ereOn
    Hi, My GUI project in Qt has a lot of "configuration pages" classes which all inherit directly from QWidget. Recently, I realized that all these classes share 2 commons slots (loadSettings() and saveSettings()). Regarding this, I have two questions: Does it make sense to write a intermediate base abstract class (lets name it BaseConfigurationPage) with these two slots as virtual pure methods ? (Every possible configuration page will always have these two methods, so I would say "yes") Before I do the heavy change in my code (if I have to) : does Qt support virtual pure slots ? Is there anything I should be aware of ? Here is a code example describing everything: class BaseConfigurationPage : public QWidget { // Some constructor and other methods, irrelevant here. public slots: virtual void loadSettings() = 0; virtual void saveSettings() = 0; }; class GeneralConfigurationPage : public BaseConfigurationPage { // Some constructor and other methods, irrelevant here. public slots: void loadSettings(); void saveSettings(); };

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  • 'Static/Constant' business ojects

    - by UpTheCreek
    I don't quite know how to ask this question, so I'll phase it as an example: Imagine in an application you have a Country object. There are two properties of this object: Name, and a 'Bordering Countries' collection. More properties might be added later, but it will be the kind of information that would change very rarely (e.g. changes of country names/borders) Lets say this application needs to know about all of the countries in the world. Where would you store these object's state? How would you new them up? It seems silly to store all this state in the DB, since it won't change very often. One option might be to have an abstract 'country' base object, and have a class for each country inheriting from this with the details of each country. But this doesn't seem quite right to me. What is the proper way of dealing with these kinds of objects?

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  • How to install libcrypt-ssleay-perl in Ubuntu?

    - by Deqing
    When I tried to install libcrypt-ssleay-perl, it says: $ sudo apt-get install libcrypt-ssleay-perl Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: libcrypt-ssleay-perl : Depends: perlapi-5.12.4 but it is not installable E: Unable to correct problems, you have held broken packages. This perlapi-5.12.4 is actually a virtual package provided by perl-base, which I had already installed: $ dpkg -l|grep perl-base ii perl-base 5.14.2-6ubuntu2.1 minimal Perl system So what should I do to install libcrypt-ssleay-perl now?

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  • How to let Linux Python application handle termination on user logout correctly?

    - by tuxpoldo
    I have written a Linux GUI application in Python that needs to do some cleanup tasks before being terminated when the user logs out. Unfortunately it seems, that on logout, all applications are killed. I tried both to handle POSIX signals and DBUS notifications, but nothing worked. Any idea what I could have made wrong? On application startup I register some termination handlers: # create graceful shutdown mechanisms signal.signal(signal.SIGTERM, self.on_signal_term) self.bus = dbus.SessionBus() self.bus.call_on_disconnection(self.on_session_disconnect) When the user logs out, neither self.on_signal_term nor self.on_session_disconnect are called. The problem occurs in several scenarios: Ubuntu 14.04 with Unity, Debian Wheezy with Gnome. Full code: https://github.com/tuxpoldo/btsync-deb/tree/master/btsync-gui

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  • How can I filter images and use filesystemview icons in my jtree?

    - by HoLeX
    First of all sorry about my english. So, i have some problems with my JTree because i want to filter specific types of images and also i want to use icons of FileSystemView class. Can you help me? I will appreciate so much. Here is my code: import java.awt.BorderLayout; import java.io.File; import java.util.Iterator; import java.util.Vector; import javax.swing.JPanel; import javax.swing.JTree; import javax.swing.event.TreeModelEvent; import javax.swing.event.TreeModelListener; import javax.swing.event.TreeSelectionEvent; import javax.swing.event.TreeSelectionListener; import javax.swing.tree.TreeModel; import javax.swing.tree.TreePath; public class ArbolDirectorio extends JPanel { private JTree fileTree; private FileSystemModel fileSystemModel; public ArbolDirectorio(String directory) { this.setLayout(new BorderLayout()); this.fileSystemModel = new FileSystemModel(new File(directory)); this.fileTree = new JTree(fileSystemModel); this.fileTree.setEditable(true); this.fileTree.addTreeSelectionListener(new TreeSelectionListener() { @Override public void valueChanged(TreeSelectionEvent event) { File file = (File) fileTree.getLastSelectedPathComponent(); System.out.println(getFileDetails(file)); } }); this.add(fileTree, BorderLayout.CENTER); } private String getFileDetails(File file) { if (file == null) { return ""; } StringBuffer buffer = new StringBuffer(); buffer.append("Name: " + file.getName() + "\n"); buffer.append("Path: " + file.getPath() + "\n"); return buffer.toString(); } } class FileSystemModel implements TreeModel { private File root; private Vector listeners = new Vector(); public FileSystemModel(File rootDirectory) { root = rootDirectory; } @Override public Object getRoot() { return root; } @Override public Object getChild(Object parent, int index) { File directory = (File) parent; String[] children = directory.list(); return new TreeFile(directory, children[index]); } @Override public int getChildCount(Object parent) { File file = (File) parent; if (file.isDirectory()) { String[] fileList = file.list(); if (fileList != null) { return file.list().length; } } return 0; } @Override public boolean isLeaf(Object node) { File file = (File) node; return file.isFile(); } @Override public int getIndexOfChild(Object parent, Object child) { File directory = (File) parent; File file = (File) child; String[] children = directory.list(); for (int i = 0; i < children.length; i++) { if (file.getName().equals(children[i])) { return i; } } return -1; } @Override public void valueForPathChanged(TreePath path, Object value) { File oldFile = (File) path.getLastPathComponent(); String fileParentPath = oldFile.getParent(); String newFileName = (String) value; File targetFile = new File(fileParentPath, newFileName); oldFile.renameTo(targetFile); File parent = new File(fileParentPath); int[] changedChildrenIndices = { getIndexOfChild(parent, targetFile) }; Object[] changedChildren = { targetFile }; fireTreeNodesChanged(path.getParentPath(), changedChildrenIndices, changedChildren); } private void fireTreeNodesChanged(TreePath parentPath, int[] indices, Object[] children) { TreeModelEvent event = new TreeModelEvent(this, parentPath, indices, children); Iterator iterator = listeners.iterator(); TreeModelListener listener = null; while (iterator.hasNext()) { listener = (TreeModelListener) iterator.next(); listener.treeNodesChanged(event); } } @Override public void addTreeModelListener(TreeModelListener listener) { listeners.add(listener); } @Override public void removeTreeModelListener(TreeModelListener listener) { listeners.remove(listener); } private class TreeFile extends File { public TreeFile(File parent, String child) { super(parent, child); } @Override public String toString() { return getName(); } } }

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  • .NET Forms Abstraction for WPF, Silverlight, Winforms, WebForms, etc...

    - by tyndall
    Anyone know of a project(s) that seek to abstract form definitions on level higher than WPF, Silverlight, Winforms, WebForms, etc... I'm working on a project where we are fixing up 16 somewhat simple WebForms. But we may convert (and probably will convert to WPF or Silverlight 3 to 4 months from now. I'd rather define these forms once and be done with it. I'm willing to write a small DSL to help define forms, subforms, validation, links, and popups. I'm only looking to solve this for 80% or 90% of the forms. Four are very complicated and I'm willing to hand code these. I guess I'm looking for something like what XUL had hoped to be.

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  • using modrewrite to change http to https? (not redirect)

    - by PaulHanak
    This might sound a little crazy, but bare with me. I basically have an include file, lets say inc-navigation.html, that has absolute paths (http://www.pathtoimage.com/image.com) that are on EVERY PAGE. Well, using SSL, I can't use that same include file because it is not referencing https:// What a pain! SO, I was maybe thinking of using htaccess to do a url rewrite of all references of HTTP to HTTPS when the browser requests a https page. Again, just to be clear, I don't want to "redirect", just "replace". So, I have this.... RewriteCond %{HTTPS} !=on RewriteRule ^http$ https but it doesn't seem to be working. I probably have the syntax wrong though. :) Of course, this is even if this type of thing is even possible!?

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  • designing multi module J2EE application

    - by user728947
    Might be my question is abstract or out of context, but i am asking here since i have little idea how this happens. I am wondering how big application/ platform break down there application in to multiple module and how they able to manage modules dependencies. For example in some E-commerce application they tend to break down it in various modules like pricing,promotions,shipping.import/export and many more. when we develop those application we hardly think about the underlying modules and how they have been designed to provides functionalists. Most of those module are not web-applications but are standalone module and not deployed in the web-app as jar files. can any one help me to understand how they break up things or is there any standard way to do this.any help/resources to get insight will really be helpful

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  • Question about domain models & their visibility...

    - by Another SO User
    I was involved in an interesting debate about the visibility of domain models & was wondering if people here have any good guidance. Per my understanding of MDA, we need not expose the domain model throughout the application layers & tiers The reason being that any change to the domain model has an impact in the overall application The wise thing to do would be to expose light-weight object (DTO's) which are a small sub-set of the domain model to abstract the actual model On the flip side, any change to the domain model would mean changing various DTO's throughout the application for the change to be visible, while if we do expose the domain model, then the change is in a single location Hope to see some comments & thoughts about this. Appreciate all the help!

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  • How to find all photos taken in April - any April?

    - by Mawg
    I have 100+ gB of photos going back 25 years. They are arranged in a directory tree by category, with nested sub-directories. How can I make a search for all photos taken in a given month, say April, in any of those directories? I don't think that a Windows search will work as that will probably be the file creation data, which could be a month or two later wen I finally more the files from SD card to PC. Perhaps searching the EXIF data? Is there a free program which can do that?

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  • Interface with generic parameters- can't get it to compile

    - by user997112
    I have an interface like so: public interface MyInterface<E extends Something1> { public void meth1(MyClass1<E> x); } and I have a subclass whose superclass implements the above interface: public class MyClass2<E extends Something1> extends Superclass{ public MyClass2(){ } public void meth1(MyClass1 x) { // TODO Auto-generated method stub } } superclass: public abstract class Superclass<E extends Something1> implements MyInterface{ MyClass1<E> x; protected E y; public Superclass(){ } } the problem is that the parameter for meth1() is supposed to be generic. If I do MyClass1 it doesn't like it and the only way I can get it to compile is by leaving out generic parameters- which feels wrong. What's going wrong?

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  • gwt - Using List<Serializable> in a RPC call?

    - by Garagos
    I have a RPC service with the following method: public List<Serializable> myMethod(TransactionCall call) {...} But I get a warning when this method is analyzed, and then the rpc call fails Analyzing 'my.project.package.myService' for serializable types Analyzing methods: public abstract java.util.List<java.io.Serializable> myMethod(my.project.package.TransactionCall call) Return type: java.util.List<java.io.Serializable> [...] java.io.Serializable Verifying instantiability (!) Checking all subtypes of Object wich qualify for serialization It seems I can't use Serializable for my List... I could use my own interface instead (something like AsyncDataInterface, wich implements the Serializable interface) but the fact is that my method will return a list custom objects AND basic objects (such as Strings, int....). So my questions are: Is it a standart behaviour? (I can't figure out why I can't use this interface in that case) Does anyone have a workaround for that kind of situation?

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  • How to force Windows XP to rename a file with a special character?

    - by codeLes
    I have a song that Windows can't play because there is a question mark in the name of the file. "Where Have All the Cowboys Gone?.ogg" // as an example So I try to rename it and Windows complains whether I try it in Explorer or from command prompt. Error I get when trying to copy, rename, or move is: The Filename, directory name, or volume label syntax is incorrect Is there a Windows way to force a rename in this case? Update I'll keep an eye on this question, but after 13 answers and many attempts (aside form 3rd party solutions) it seems that Windows can't do this (or at least my windows can't, no short names). So I'm accepting the answer which was my original solution anyway of using Linux. It would be nice to see Windows handle this somehow, so don't stop just because I've accepted this answer, the question still stands!

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  • jquery parent/children selector for counting <li>

    - by Kreker
    Hi. I have this piece of HTML <div id="fileTreeInviati"> <ul class="php-file-tree"> <li class="pft-directory"> <a href="#" class="" name="101">A006 - SOMETEXT (<span name="contaNew"></span>)</a> <img src="./moduli/home/images/info.png" title="Informazioni Azienda" class="imgInfo"/> <ul style="display: none;"> <li class="pft-file ext-png"> <a href="javascript:getInfoFile('4');" class="" id="4">cut.png</a> </li> <li class="pft-file ext-dll"> <a href="javascript:getInfoFile('27');" class="new" id="27">Safari.dll</a> </li> </ul> </li> <li class="pft-directory"> <a href="#" class="" name="102">A012 - SOMETEXT (<span name="contaNew"></span>)</a> <img src="./moduli/home/images/info.png" title="Informazioni Azienda" class="imgInfo"/> <ul style="display: none;"> <li class="pft-file ext-jpg"> <a href="javascript:getInfoFile('19');" class="new" id="19">04.jpg</a> </li> <li class="pft-file ext-dll"> <a href="javascript:getInfoFile('24');" class="new" id="24">Safari.dll</a> </li> </ul> </li> <li class="pft-directory"> <a href="#" class="" name="103">A014 - SOMETEXT (<span name="contaNew"></span>)</a> <img src="./moduli/home/images/info.png" title="Informazioni Azienda" class="imgInfo"/> <ul style="display: none;"> <li class="pft-file ext-txt"> <a href="javascript:getInfoFile('17');" class="new" id="17">acu.txt</a> </li> <li class="pft-file ext-dll"> <a href="javascript:getInfoFile('22');" class="new" id="22">Safari.dll</a> </li> </ul> </li> </ul> I'm working on a js snippet that cycle through all "a" of the "li" and checks if it has the class "new" if yes increment a counter by one. This counter now has to be printed on the relative "li" "span" 3 level before. So I have the number of the element with the "new" class. The js snippet is this $("#fileTreeInviati .php-file-tree .pft-directory li").each(function(){ $(this).children("a").each(function(i,e){ if ($(e).hasClass("new")){ cont++; console.log($(e).text()); $(this).parent().parent().parent().children("a").children("span").text(cont); } }) cont = 0; }); I think I'm almost there but the counter is always 1. I think there is something mess with .children, maybe it can handle only the first occurrence? Thanks for help

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