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• Flowchart for solving programming problems

  - by nurne

  I noticed that every developer implements a somewhat different flowchart for solving programming problems. By flowchart I mean a defined system of techniques that the developer goes through in a certain sequence, trying to solve the problem at hand. Some examples for techniques: Google "how to..." or "... tutorial". Search the java/msdn/apple/etc API doc for the specific class or method. Search in stack overflow the exact problem with some tags like [iphone]/[java] etc. Take a nap and let the subconscious work. Debug. Draw the algorithm or system. Google the logged error message. Ask a colleague or manager. Ask a new question in stack overflow. From your experience, what is the best flowchart for solving a programming problem?

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• What are the pros and cons of a non-fixed-interval update loop?

  - by akonsu

  I am studying various approaches to implementing a game loop and I have found this article. In the article the author implements a loop which, if the processing falls behind in time, skips frame renderings and just updates the game in a loop (the last variant called "Constant Game Speed independent of Variable FPS"). I do not understand why it is acceptable to call update_game() in a loop without making sure the update function is called at a particular interval. I do not see any value in doing this. I would think that in my game I want to be sure the game is updated periodically with a known period. So maybe it is worthwhile to have two threads, one would call update periodically, and the other one would redraw the game, also periodically? Would this be a good and practical approach? Of course I would need to synchronise the threads.

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• Premera Blue Cross Deploys PeopleSoft Enterprise 9.1 Human Capital Management, Financial Management, Enterprise Learning Management and Enterprise Portal Solutions

  - by jay.richey

  Optimum Solutions Implements Oracle's PeopleSoft Enterprise 9.1 at Premera Blue Cross Premera chose to upgrade to the latest version of PeopleSoft to help the company achieve its strategic goals, which include building and maintaining a skilled employee team that enables the company to deliver highly efficient and valuable service to plan subscribers, sponsors, and healthcare providers. Its decision was influenced by the key capabilities in PeopleSoft Talent Management 9.1, as well as the common technology enhancements for the PeopleSoft PeopleTools 8.50 toolset across all business process areas, which has helped Premera to maximize process automation, increased ease of use, and minimize long term IT support overhead. Read more...

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• Trick Ubuntu into resolving a domain name locally

  - by Matthew Brown

  I have an Ubuntu box that I use for all sorts of things. One thing I really want to do is redirect a sub domain to a local script. For example thisbit.example.com should actually show the content from localhost/~USER/FAKE.thisbit.example.com/ which is a folder that Apache is running for me which contains a very simple PHP script which implements an offline version of a server script that I am testing against. But example.com should continue to behave normally as should notthisbit.example.com etc. Ideally I need to be able to switch from testing to live with minimal fuss when the time comes.

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• Quality Assurance tools discrepancies

  - by Roudak

  It is a bit ironic, yesterday I answered a question related to this topic that was marked to be good and today I'm the one who asks. These are my thoughts and a question: Also let's agree on the terms: QA is a set of activities that defines and implements processes during SW development. The common tool is the process audit. However, my colleague at work agrees with the opinion that reviews and inspections are also quality assurance tools, although most sources classify them as quality control. I would say both sides are partially right: during inspections, we evaluate a physical product (clearly QC) but we see it as a white box so we can check its compliance with set processes (QA). Do you think it is the reason of the dichotomy among the authors? I know it is more like an academic question but it deserves the answer :)

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• Type Conversion in JPA 2.1

  - by delabassee

  The Java Persistence 2.1 specification (JSR 338) adds support for various new features such as schema generation, stored procedure invocation, use of entity graphs in queries and find operations, unsynchronized persistence contexts, injection into entity listener classes, etc. JPA 2.1 also add support for Type Conversion methods, sometime called Type Converter. This new facility let developers specify methods to convert between the entity attribute representation and the database representation for attributes of basic types. For additional details on Type Conversion, you can check the JSR 338 Specification and its corresponding JPA 2.1 Javadocs. In addition, you can also check those 2 articles. The first article ('How to implement a Type Converter') gives a short overview on Type Conversion while the second article ('How to use a JPA Type Converter to encrypt your data') implements a simple use-case (encrypting data) to illustrate Type Conversion. Mission critical applications would probably rely on transparent database encryption facilities provided by the database but that's not the point here, this use-case is easy enough to illustrate JPA 2.1 Type Conversion.

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• Implementing Ads on any page in your Windows 8 XAML app–part 1

  - by nmarun

  Let’s look at how you can implements ads on any page in your win 8 app. Before you get to your application, you need to create Ad Units in the MS Pubcenter site. Once you have set up your account with payout and tax details, go to the Setup tab and you’ll see something like below. There are a few options for the sizes of the ad units as shown on the Pubcenter site. Remember that these screenshots are just to give you some reference. The actual positioning of the ads in your apps is decided by you...(read more)

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• How should I access frame buttons from a controller in an MVC approach?

  - by Loris

  I'm developing an italian card game using the mvc pattern. I have the class GameFrame that contains the view. The user's card are buttons (JButton objects). I have 3 controllers: GameController: to control the game in general. Contains the game loop. HumanPlayerController: to control the user input ComputerPlayerController: contains the AI of the computer PlayerController: is an interface with the makeTurn() method. It's implemented by HumanP.C. and ComputerP.C. HumanPlayerController implements ActionListener too. But what is the right way to access to the GameFrame buttons? I need it for understand which card was chosen. GameFrame and HumanPlayerController are in different packages. Should i make the JButtons public?

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• How to simulate a USB plug?

  - by Nicolas Delvaux

  I have an app that implements some automations when an USB key is plugged. While developing, I have to test it in a specific environment (derivative from Debian Squeeze). The app subscribe to HAL events via DBUS. The problem is: my desk is on the third floor while my test machines are in the basement. I would really like to have a way to simulate a USB plug. usbip does not work on Ubuntu. I can't manage to use the g_mass_storage module on Ubuntu (I lack the dummy_hcd module) and in Debian. Maybe it is possible to simulate a dbus call? My work station is on Ubuntu 12.04.

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• Tester/Doer pattern: Assume the caller conforms to the pattern or be defensive and repeat the check?

  - by Daniel Hilgarth

  Assume a simple class that implements the Tester/Doer pattern: public class FooCommandHandler : ICommandHandler { public bool CanHandle(object command) { return command is FooCommand; } public void Handle(object command) { var fooCommand = (FooCommand)command; // Do something with fooCommand } } Now, if someone doesn't conform to the pattern and calls Handle without verifying the command via CanHandle, the code in Handle throws an exception. However, depending on the actual implementation of Handle this can be a whole range of different exceptions. The following implementation would check CanHandle again in Handle and throw a descriptive exception: public void Handle(object command) { if(!CanHandle(command)) throw new TesterDoerPatternUsageViolationException("Please call CanHandle first"); // actual implementation of handling the command. } This has the advantage that the exception is very descriptive. It has the disadvantage that CanHandle is called twice for "good" clients. Is there a consensus on which variation should be used?

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• Java best practice Interface - subclasses and constants

  - by Taiko

  In the case where a couple of classes implements an interface, and those classes have a couple of constants in common (but no functions), were should I put this constant ? I've had this problem a couple of times. I have this interface : DataFromSensors that I use to hide the implementations of several sub classes like DataFromHeartRateMonitor DataFromGps etc... For some reason, those classes uses the same constants. And there's nowere else in the code were it is used. My question is, were should I put those constants ? Not in the interface, because it has nothing to do with my API Not in a static Constants class, because I'm trying to avoid those Not in a common abstract class, that would stand between the interface and the subclasses, because I have no functions in common, only a couple of constants (TIMEOUT_DURATION, UUID, those kind of things) I've read best practice for constants and interface to define constants but they don't really answer my question. Thanks !

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• Viewing the NetBeans Central Registry (Part 2)

  - by Geertjan

  Jens Hofschröer, who has one of the very best NetBeans Platform blogs (if you more or less understand German), and who wrote, sometime ago, the initial version of the Import Statement Organizer, as well as being the main developer of a great gear design & manufacturing tool on the NetBeans Platform in Aachen, commented on my recent blog entry "Viewing the NetBeans Central Registry", where the root Node of the Central Registry is shown in a BeanTreeView, with the words: "I wrapped that Node in a FilterNode to provide the 'position' attribute and the 'file extension'. All Children are wrapped too. Then I used an OutlineView to show these two properties. Great tool to find wrong layer entries." I asked him for the code he describes above and he sent it to me. He discussed it here in his blog, while all the code involved can be read below. The result is as follows, where you can see that the OutlineView shows information that my simple implementation (via a BeanTreeView) kept hidden: And so here is the definition of the Node. class LayerPropertiesNode extends FilterNode { public LayerPropertiesNode(Node node) { super(node, isFolder(node) ? Children.create(new LayerPropertiesFactory(node), true) : Children.LEAF); } private static boolean isFolder(Node node) { return null != node.getLookup().lookup(DataFolder.class); } @Override public String getDisplayName() { return getLookup().lookup(FileObject.class).getName(); } @Override public Image getIcon(int type) { FileObject fo = getLookup().lookup(FileObject.class); try { DataObject data = DataObject.find(fo); return data.getNodeDelegate().getIcon(type); } catch (DataObjectNotFoundException ex) { Exceptions.printStackTrace(ex); } return super.getIcon(type); } @Override public Image getOpenedIcon(int type) { return getIcon(type); } @Override public PropertySet[] getPropertySets() { Set set = Sheet.createPropertiesSet(); set.put(new PropertySupport.ReadOnly<Integer>( "position", Integer.class, "Position", null) { @Override public Integer getValue() throws IllegalAccessException, InvocationTargetException { FileObject fileEntry = getLookup().lookup(FileObject.class); Integer posValue = (Integer) fileEntry.getAttribute("position"); return posValue != null ? posValue : Integer.valueOf(0); } }); set.put(new PropertySupport.ReadOnly<String>( "ext", String.class, "Extension", null) { @Override public String getValue() throws IllegalAccessException, InvocationTargetException { FileObject fileEntry = getLookup().lookup(FileObject.class); return fileEntry.getExt(); } }); PropertySet[] original = super.getPropertySets(); PropertySet[] withLayer = new PropertySet[original.length + 1]; System.arraycopy(original, 0, withLayer, 0, original.length); withLayer[withLayer.length - 1] = set; return withLayer; } private static class LayerPropertiesFactory extends ChildFactory<FileObject> { private final Node context; public LayerPropertiesFactory(Node context) { this.context = context; } @Override protected boolean createKeys(List<FileObject> list) { FileObject folder = context.getLookup().lookup(FileObject.class); FileObject[] children = folder.getChildren(); List<FileObject> ordered = FileUtil.getOrder(Arrays.asList(children), false); list.addAll(ordered); return true; } @Override protected Node createNodeForKey(FileObject key) { AbstractNode node = new AbstractNode(org.openide.nodes.Children.LEAF, key.isFolder() ? Lookups.fixed(key, DataFolder.findFolder(key)) : Lookups.singleton(key)); return new LayerPropertiesNode(node); } } } Then here is the definition of the Action, which pops up a JPanel, displaying an OutlineView: @ActionID(category = "Tools", id = "de.nigjo.nb.layerview.LayerViewAction") @ActionRegistration(displayName = "#CTL_LayerViewAction") @ActionReferences({ @ActionReference(path = "Menu/Tools", position = 1450, separatorBefore = 1425) }) @Messages("CTL_LayerViewAction=Display XML Layer") public final class LayerViewAction implements ActionListener { @Override public void actionPerformed(ActionEvent e) { try { Node node = DataObject.find(FileUtil.getConfigRoot()).getNodeDelegate(); node = new LayerPropertiesNode(node); node = new FilterNode(node) { @Override public Component getCustomizer() { LayerView view = new LayerView(); view.getExplorerManager().setRootContext(this); return view; } @Override public boolean hasCustomizer() { return true; } }; NodeOperation.getDefault().customize(node); } catch (DataObjectNotFoundException ex) { Exceptions.printStackTrace(ex); } } private static class LayerView extends JPanel implements ExplorerManager.Provider { private final ExplorerManager em; public LayerView() { super(new BorderLayout()); em = new ExplorerManager(); OutlineView view = new OutlineView("entry"); view.addPropertyColumn("position", "Position"); view.addPropertyColumn("ext", "Extension"); add(view); } @Override public ExplorerManager getExplorerManager() { return em; } } }

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• Request of some opinions about a vertical menu style and some suggestions for the site style [on hold]

  - by AndreaNobili

  I am developing a simple mainly static website using WordPress (because maybe in the future I will add some dynamic content) for a company. The new site have to follow the structure of the old site that requires the presence of a vertical main menu in the left column that contains the link to all the statics pages in the site. This is the old site structure: http://www.saranistri.com/ Now I have installed a new WordPress test site (this is only a test site): http://onofri.org/example/ As you can see in the left columns I have put two main menu vetical widgets that implements a possible choise for the maun menù (the top menù upon the header must be eliminated in the final implementation) I want to know some opinions about: 1) Which of the two version is better? Do you have some additional ideas about the CSS style of this vertical menu? 2) What could I do to give a more professional look to this site? (I know that I have to insert a logo into the header) Tnx Andrea

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• Synchronized Property Changes (Part 4)

  - by Geertjan

  The next step is to activate the undo/redo functionality... for a Node. Something I've not seen done before. I.e., when the Node is renamed via F2 on the Node, the "Undo/Redo" buttons should start working. Here is the start of the solution, via this item in the mailing list and Timon Veenstra's BeanNode class, note especially the items in bold: public class ShipNode extends BeanNode implements PropertyChangeListener, UndoRedo.Provider { private final InstanceContent ic; private final ShipSaveCapability saveCookie; private UndoRedo.Manager manager; private String oldDisplayName; private String newDisplayName; private Ship ship; public ShipNode(Ship bean) throws IntrospectionException { this(bean, new InstanceContent()); } private ShipNode(Ship bean, InstanceContent ic) throws IntrospectionException { super(bean, Children.LEAF, new ProxyLookup(new AbstractLookup(ic), Lookups.singleton(bean))); this.ic = ic; setDisplayName(bean.getType()); setShortDescription(String.valueOf(bean.getYear())); saveCookie = new ShipSaveCapability(bean); bean.addPropertyChangeListener(WeakListeners.propertyChange(this, bean)); } @Override public Action[] getActions(boolean context) { List<? extends Action> shipActions = Utilities.actionsForPath("Actions/Ship"); return shipActions.toArray(new Action[shipActions.size()]); } protected void fire(boolean modified) { if (modified) { ic.add(saveCookie); } else { ic.remove(saveCookie); } } @Override public UndoRedo getUndoRedo() { manager = Lookup.getDefault().lookup( UndoRedo.Manager.class); return manager; } private class ShipSaveCapability implements SaveCookie { private final Ship bean; public ShipSaveCapability(Ship bean) { this.bean = bean; } @Override public void save() throws IOException { StatusDisplayer.getDefault().setStatusText("Saving..."); fire(false); } } @Override public boolean canRename() { return true; } @Override public void setName(String newDisplayName) { Ship c = getLookup().lookup(Ship.class); oldDisplayName = c.getType(); c.setType(newDisplayName); fireNameChange(oldDisplayName, newDisplayName); fire(true); fireUndoableEvent("type", ship, oldDisplayName, newDisplayName); } public void fireUndoableEvent(String property, Ship source, Object oldValue, Object newValue) { ReUndoableEdit reUndoableEdit = new ReUndoableEdit( property, source, oldValue, newValue); UndoableEditEvent undoableEditEvent = new UndoableEditEvent( this, reUndoableEdit); manager.undoableEditHappened(undoableEditEvent); } private class ReUndoableEdit extends AbstractUndoableEdit { private Object oldValue; private Object newValue; private Ship source; private String property; public ReUndoableEdit(String property, Ship source, Object oldValue, Object newValue) { super(); this.oldValue = oldValue; this.newValue = newValue; this.source = source; this.property = property; } @Override public void undo() throws CannotUndoException { setName(oldValue.toString()); } @Override public void redo() throws CannotRedoException { setName(newValue.toString()); } } @Override public String getDisplayName() { Ship c = getLookup().lookup(Ship.class); if (null != c.getType()) { return c.getType(); } return super.getDisplayName(); } @Override public String getShortDescription() { Ship c = getLookup().lookup(Ship.class); if (null != String.valueOf(c.getYear())) { return String.valueOf(c.getYear()); } return super.getShortDescription(); } @Override public void propertyChange(PropertyChangeEvent evt) { if (evt.getPropertyName().equals("type")) { String oldDisplayName = evt.getOldValue().toString(); String newDisplayName = evt.getNewValue().toString(); fireDisplayNameChange(oldDisplayName, newDisplayName); } else if (evt.getPropertyName().equals("year")) { String oldToolTip = evt.getOldValue().toString(); String newToolTip = evt.getNewValue().toString(); fireShortDescriptionChange(oldToolTip, newToolTip); } fire(true); } } Undo works when rename is done, but Redo never does, because Undo is constantly activated, since it is reactivated whenever there is a name change. And why must the UndoRedoManager be retrieved from the Lookup (it doesn't work otherwise)? Don't get that part of the code either. Help welcome!

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• Dynamic Strategy Pattern [migrated]

  - by Karl Barker

  So I'm writing a web service architecture which includes FunctionProvider classes which do the actual processing of requests, and a main Endpoint class which receives and delegates requests to the proper FunctionProvider. I don't know exactly the FunctionProviders available at runtime, so I need to be able to 'register' (if that's the right word) them with my main Endpoint class, and query them to see if they match an incoming request. public class MyFunc implements FunctionProvider{ static { MyEndpoint.register(MyFunc); } public Boolean matchesRequest(Request req){...} public void processRequest(Request req){...} } public class MyEndpoint{ private static ArrayList<FunctionProvider> functions = new ArrayList<FunctionProvider>(); public void register(Class clz){ functions.add(clz); } public void doPost(Request request){ //find the FunctionProvider in functions //matching the request } } I've really not done much reflective Java like this (and the above is likely wrong, but hopefully demonstrates my intentions). What's the nicest way to implement this without getting hacky?

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• What is the good way of sharing specific data between ViewModels

  - by voroninp

  We have IAppContext which is injected into ViewModel. This service contains shared data: global filters and other application wide properties. But there are cases when data is very specific. For example one VM implements Master and the second one - Details of selected tree item. Thus DetailsVm must know about the selected item and its changes. We can store this information either in IAppContext or inside each concerned VM. In both cases update notifications are sent via Messenger. I see pros and cons for any of the approaches and can not decide which one is better. 1st: + explicitly exposed shared proerties, easy to follow dependencies - IAppContxt becomes cluttered with very specific data. 2nd: the exact opposite of the first and more memory load due to data duplication. May be someone can offer design alternatives or tell that one of the variants is objectively superior to the other cause I miss something important?

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• UndoRedo on Nodes (Part 2)

  - by Geertjan

  After the recording of the latest API Design Tip for the upcoming NetBeans Podcast, Jaroslav Tulach helped me with the problem I blogged about yesterday. First he expressed surprise at seeing Undo/Redo work on Nodes, which was never the intention, i.e., that feature was always intended for documents, e.g., the Java editor. However, he then showed me where to find the Properties window in the NetBeans sources, where it is org.netbeans.core.windows.view.ui.NbSheet. It turns out that the Properties window does not have an activated node and hence the Node that implements UndoRedo.Manager is never put in the Lookup. Once we added, on line 303, "this.setActivatedNodes(nodes);", everything worked as expected, i.e., the Undo/Redo actions are now enabled, even when the Properties window is selected: Maybe it means I should file an issue to get that line added to NbSheet?

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• Which version of OpenGL for Android?

  - by akadouri

  I've been trying to learn OpenGL ES 2.0 to create a simple 2D game. I bought a book on android development, but after seeing that the author uses his own SDK that implements OpenGL ES 1.0 I decided to just use online tutorials. I've been so lost trying to find out what to use. The Matrices and shaders of 2.0 confuse me and I can't find any tutorial that just explains how to texture map a simple 2D image. Basically: OpenGL ES 1.x or 2.0 for simple 2D with little OpenGL experience If 2.0 Any good tutorials for 2.0, I've found so many for 1.0

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• How to make this design closer to proper DDD?

  - by Seralize

  I've read about DDD for days now and need help with this sample design. All the rules of DDD make me very confused to how I'm supposed to build anything at all when domain objects are not allowed to show methods to the application layer; where else to orchestrate behaviour? Repositories are not allowed to be injected into entities and entities themselves must thus work on state. Then an entity needs to know something else from the domain, but other entity objects are not allowed to be injected either? Some of these things makes sense to me but some don't. I've yet to find good examples of how to build a whole feature as every example is about Orders and Products, repeating the other examples over and over. I learn best by reading examples and have tried to build a feature using the information I've gained about DDD this far. I need your help to point out what I do wrong and how to fix it, most preferably with code as "I would not recomment doing X and Y" is very hard to understand in a context where everything is just vaguely defined already. If I can't inject an entity into another it would be easier to see how to do it properly. In my example there are users and moderators. A moderator can ban users, but with a business rule: only 3 per day. I did an attempt at setting up a class diagram to show the relationships (code below): interface iUser { public function getUserId(); public function getUsername(); } class User implements iUser { protected $_id; protected $_username; public function __construct(UserId $user_id, Username $username) { $this->_id = $user_id; $this->_username = $username; } public function getUserId() { return $this->_id; } public function getUsername() { return $this->_username; } } class Moderator extends User { protected $_ban_count; protected $_last_ban_date; public function __construct(UserBanCount $ban_count, SimpleDate $last_ban_date) { $this->_ban_count = $ban_count; $this->_last_ban_date = $last_ban_date; } public function banUser(iUser &$user, iBannedUser &$banned_user) { if (! $this->_isAllowedToBan()) { throw new DomainException('You are not allowed to ban more users today.'); } if (date('d.m.Y') != $this->_last_ban_date->getValue()) { $this->_ban_count = 0; } $this->_ban_count++; $date_banned = date('d.m.Y'); $expiration_date = date('d.m.Y', strtotime('+1 week')); $banned_user->add($user->getUserId(), new SimpleDate($date_banned), new SimpleDate($expiration_date)); } protected function _isAllowedToBan() { if ($this->_ban_count >= 3 AND date('d.m.Y') == $this->_last_ban_date->getValue()) { return false; } return true; } } interface iBannedUser { public function add(UserId $user_id, SimpleDate $date_banned, SimpleDate $expiration_date); public function remove(); } class BannedUser implements iBannedUser { protected $_user_id; protected $_date_banned; protected $_expiration_date; public function __construct(UserId $user_id, SimpleDate $date_banned, SimpleDate $expiration_date) { $this->_user_id = $user_id; $this->_date_banned = $date_banned; $this->_expiration_date = $expiration_date; } public function add(UserId $user_id, SimpleDate $date_banned, SimpleDate $expiration_date) { $this->_user_id = $user_id; $this->_date_banned = $date_banned; $this->_expiration_date = $expiration_date; } public function remove() { $this->_user_id = ''; $this->_date_banned = ''; $this->_expiration_date = ''; } } // Gathers objects $user_repo = new UserRepository(); $evil_user = $user_repo->findById(123); $moderator_repo = new ModeratorRepository(); $moderator = $moderator_repo->findById(1337); $banned_user_factory = new BannedUserFactory(); $banned_user = $banned_user_factory->build(); // Performs ban $moderator->banUser($evil_user, $banned_user); // Saves objects to database $user_repo->store($evil_user); $moderator_repo->store($moderator); $banned_user_repo = new BannedUserRepository(); $banned_user_repo->store($banned_user); Should the User entitity have a 'is_banned' field which can be checked with $user->isBanned();? How to remove a ban? I have no idea.

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• Workflow of sharing code for small teams

  - by Mihalis Bagos

  Problem is, we have developed a small CMS, that is different per implementation (currently). Of course development of this is never complete. Sometimes, we are working on more than one project that implements it (by copying-pasting the code files of the CMS to each project), and we add a new feature that we want to share on other projects as well (these can be small ones too, ie a custom ajax JSON controller - we use MVC) What we want to do is quickly and uniformly share the code with all other projects, via a version control system (or something similar), and generally organize the workflow as we know this isn't a very good workflow that we have. What would you suggest? Also, at the momment, the software we use is Visual Studio 2010, so we are strongly considering TFS, but even if we get it we still don't know the ideal workflow, or even if TFS supports what we want to do. Edit: Also note, we have specific implementations that have modifications over the CMS base that we want to KEEP only in the project area. (ie: a specific feature that we DONT want to share with the base CMS code)

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• How can I derive force vectors from velocity vectors?

  - by PixelRouter

  I'm making a 2d shooter ala Geometry Wars. I've got my own simple physics at work driving the background grid and all my entities. To move anything in the world I apply a Vector2d force to it. The 'engine' calculates the resulting acceleration and therefore the velocity. I am trying to port some code I found which implements the classic 'Boids' flocking algorithm, but the code I have works by calculating the Boids' velocities directly, so If i use it as is, it bypasses my physics engine. How I can translate the velocity vectors into force vectors that I can apply to the Boids and which will result in the proper velocities via my physics engine.

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• Row Versioning Concurrency in SQL Server

  The optimistic concurrency model assumes that several concurrent transactions can usually complete without interfering with each other, and therefore do not require draconian locking on the resources they access. SQL Server 2005, and later, implements a form of this model called row versioning concurrency. It works by remembering the value of the data at the start of the transaction and checking that no other transaction has modified it before committing. If this optimism is justified for the pattern of activity within a database, it can improve performance by greatly reducing blocking. Kalen Delaney explains how it works in SQL Server.

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• Android ListView setSelection() does not seem to work.

  - by alkar

  I have a ListActivity that implements onListItemClick() and calls a doSomething() function of the class. The latter contains l.setSelection(position) where l is the ListView object. Now there is a onClickListener() listening for a button click that perfoms some actions and that too calls doSomething(). In the first case, the selected item get positioned appropriately, but in the latter, nothing happens. Any clues about this strange behaviour and how I might make it work?

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• VB.Net Dynamically Load DLL

  - by hermiod

  I am trying to write some code that will allow me to dynamically load DLLs into my application, depending on an application setting. The idea is that the database to be accessed is set in the application settings and then this loads the appropriate DLL and assigns it to an instance of an interface for my application to access. This is my code at the moment: Dim SQLDataSource As ICRDataLayer Dim ass As Assembly = Assembly. _ LoadFrom("M:\MyProgs\WebService\DynamicAssemblyLoading\SQLServer\bin\Debug\SQLServer.dll") Dim obj As Object = ass.CreateInstance(GetType(ICRDataLayer).ToString, True) SQLDataSource = DirectCast(obj, ICRDataLayer) MsgBox(SQLDataSource.ModuleName & vbNewLine & SQLDataSource.ModuleDescription) I have my interface (ICRDataLayer) and the SQLServer.dll contains an implementation of this interface. I just want to load the assembly and assign it to the SQLDataSource object. The above code just doesn't work. There are no exceptions thrown, even the Msgbox doesn't appear. I would've expected at least the messagebox appearing with nothing in it, but even this doesn't happen! Is there a way to determine if the loaded assembly implements a specific interface. I tried the below but this also doesn't seem to do anything! For Each loadedType As Type In ass.GetTypes If GetType(ICRDataLayer).IsAssignableFrom(loadedType) Then Dim obj1 As Object = ass.CreateInstance(GetType(ICRDataLayer).ToString, True) SQLDataSource = DirectCast(obj1, ICRDataLayer) End If Next EDIT: New code from Vlad's examples: Module CRDataLayerFactory Sub New() End Sub ' class name is a contract, ' should be the same for all plugins Private Function Create() As ICRDataLayer Return New SQLServer() End Function End Module Above is Module in each DLL, converted from Vlad's C# example. Below is my code to bring in the DLL: Dim SQLDataSource As ICRDataLayer Dim ass As Assembly = Assembly. _ LoadFrom("M:\MyProgs\WebService\DynamicAssemblyLoading\SQLServer\bin\Debug\SQLServer.dll") Dim factory As Object = ass.CreateInstance("CRDataLayerFactory", True) Dim t As Type = factory.GetType Dim method As MethodInfo = t.GetMethod("Create") Dim obj As Object = method.Invoke(factory, Nothing) SQLDataSource = DirectCast(obj, ICRDataLayer) EDIT: Implementation based on Paul Kohler's code Dim file As String For Each file In Directory.GetFiles(baseDir, searchPattern, SearchOption.TopDirectoryOnly) Dim assemblyType As System.Type For Each assemblyType In Assembly.LoadFrom(file).GetTypes Dim s As System.Type() = assemblyType.GetInterfaces For Each ty As System.Type In s If ty.Name.Contains("ICRDataLayer") Then MsgBox(ty.Name) plugin = DirectCast(Activator.CreateInstance(assemblyType), ICRDataLayer) MessageBox.Show(plugin.ModuleName) End If Next I get the following error with this code: Unable to cast object of type 'SQLServer.CRDataSource.SQLServer' to type 'DynamicAssemblyLoading.ICRDataLayer'. The actual DLL is in a different project called SQLServer in the same solution as my implementation code. CRDataSource is a namespace and SQLServer is the actual class name of the DLL. The SQLServer class implements ICRDataLayer, so I don't understand why it wouldn't be able to cast it. Is the naming significant here, I wouldn't have thought it would be.

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• Custom RoleProvider with MVC 2.0 webconfig

  - by Farrell

  I have a custom MembershipProvider and a custom RoleProvider. I created the custom MembershipProvider by creating a SimpleMembershipProvider class which implements the MembershipProvider class. After that I changed my web.config and works. So I used the same approach creating a custom RoleProvider. Nothing special, just creating a SimpleRoleProvider class which implements the RoleProvider class. But then when I changed the web.config file and runs the solution I get the following error message: Web.Config <membership defaultProvider="DashboardMembershipProvider"> <providers> <clear/> <add name="SimpleMembershipProvider" type="Dashboard.Web.Controlling.Account.SimpleMembershipProvider" /> </providers> </membership> <roleManager enabled="true" defaultProvider="DashboardRoleProvider"> <providers> <clear/> <add name="DashboardRoleProvider" type="Dashboard.Web.Controlling.Account.DashboardRoleProvider" /> </providers> </roleManager> Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: No parameterless constructor defined for this object. Source Error Line 78: <add name="SimpleRoleProvider" Line 79: type="Dashboard.Web.Controlling.Account.SimpleRoleProvider" /> So I searched the web. And tried on the type attribute, which generates the following errors: Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: Could not load file or assembly 'Dashboard.Web.Controlling.Account' or one of its dependencies. The system cannot find the file specified. Source Error: Line 78: <add name="SimpleRoleProvider" Line 79: type="Dashboard.Web.Controlling.Account.SimpleRoleProvider,Dashboard.Web.Controlling.Account" /> Any suggestions on how I would be able to get this CustomRoleProvider working? Any help is greatly appreciated!

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