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  • Unity - Mecanim & Rigidbody on Third Person Controller - Gravity bug?

    - by Celtc
    I'm working on a third person controller which uses physX to interact with the other objects (using the Rigidbody component) and Mecanim to animate the character. All the animations used are baked to Y, and the movement on this axis is controlled by the gravity applied by the rigidbody component. The configuration of the falling animation: And the character components configuration: Since the falling animation doesn't have root motion on XZ, I move the character on XZ by code. Like this: // On the Ground if (IsGrounded()) { GroundedMovementMgm(); // Stores the velocity velocityPreFalling = rigidbody.velocity; } // Mid-Air else { // Continue the pre falling velocity rigidbody.velocity = new Vector3(velocityPreFalling.x, rigidbody.velocity.y, velocityPreFalling.z); } The problem is that when the chracter starts falling and hit against a wall in mid air, it gets stuck to the wall. Here are some pics which explains the problems: Hope someone can help me. Thanks and sory for my bad english! PD.: I was asked for the IsGrounded() function, so I'm adding it: void OnCollisionEnter(Collision collision) { if (!grounded) TrackGrounded(collision); } void OnCollisionStay(Collision collision) { TrackGrounded(collision); } void OnCollisionExit() { grounded = false; } public bool IsGrounded() { return grounded; } private void TrackGrounded(Collision collision) { var maxHeight = capCollider.bounds.min.y + capCollider.radius * .9f; foreach (var contact in collision.contacts) { if (contact.point.y < maxHeight && Vector3.Angle(contact.normal, Vector3.up) < maxSlopeAngle) { grounded = true; break; } } } I'll also add a LINK to download the project if someone wants it.

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  • Testing Routes in ASP.NET MVC with MvcContrib

    - by Guilherme Cardoso
    I've decide to write about unit testing in the next weeks. If we decide to develop with Test-Driven Developement pattern, it's important to not forget the routes. This article shows how to test routes. I'm importing my routes from my RegisterRoutes method from the Global.asax of Project.Web created by default (in SetUp). I'm using ShouldMapTp() from MvcContrib: http://mvccontrib.codeplex.com/ The controller is specified in the ShouldMapTo() signature, and we use lambda expressions for the action and parameters that are passed to that controller. [SetUp] public void Setup() { Project.Web.MvcApplication.RegisterRoutes(RouteTable.Routes); } [Test] public void Should_Route_HomeController() { "~/Home" .ShouldMapTo<HomeController>(action => action.Index()); } [Test] public void Should_Route_EventsController() { "~/Events" .ShouldMapTo<EventsController>(action => action.Index()); "~/Events/View/44/Concert-DevaMatri-22-January-" .ShouldMapTo<EventosController>(action => action.Read(1, "Title")); // In this example,44 is the Id for my Event and "Concert-DevaMatri-22-January" is the title for that Event } [TearDown] public void teardown() { RouteTable.Routes.Clear(); }

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  • Login loop in Snow Leopard

    - by hgpc
    I can't get out of a login loop of a particular admin user. After entering the password the login screen is shown again after about a minute. Other users work fine. It started happening after a simple reboot. Can you please help me? Thank you! Tried to no avail: Change the password Remove the password Repair disk (no errors) Boot in safe mode Reinstall Snow Leopard and updating to 10.6.6 Remove content of ~/Library/Caches Removed content of ~/Library/Preferences Replaced /etc/authorization with Install DVD copy The system.log mentions a crash report. I'm including both below. system.log Jan 8 02:43:30 loginwindow218: Login Window - Returned from Security Agent Jan 8 02:43:30 loginwindow218: USER_PROCESS: 218 console Jan 8 02:44:42 kernel[0]: Jan 8 02:44:43: --- last message repeated 1 time --- Jan 8 02:44:43 com.apple.launchd[1] (com.apple.loginwindow218): Job appears to have crashed: Bus error Jan 8 02:44:43 com.apple.UserEventAgent-LoginWindow223: ALF error: cannot find useragent 1102 Jan 8 02:44:43 com.apple.UserEventAgent-LoginWindow223: plugin.UserEventAgentFactory: called with typeID=FC86416D-6164-2070-726F-70735C216EC0 Jan 8 02:44:43 /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow233: Login Window Application Started Jan 8 02:44:43 SecurityAgent228: CGSShutdownServerConnections: Detaching application from window server Jan 8 02:44:43 com.apple.ReportCrash.Root232: 2011-01-08 02:44:43.936 ReportCrash232:2903 Saved crash report for loginwindow218 version ??? (???) to /Library/Logs/DiagnosticReports/loginwindow_2011-01-08-024443_localhost.crash Jan 8 02:44:44 SecurityAgent228: MIG: server died: CGSReleaseShmem : Cannot release shared memory Jan 8 02:44:44 SecurityAgent228: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Jan 8 02:44:44 SecurityAgent228: CGSDisplayServerShutdown: Detaching display subsystem from window server Jan 8 02:44:44 SecurityAgent228: HIToolbox: received notification of WindowServer event port death. Jan 8 02:44:44 SecurityAgent228: port matched the WindowServer port created in BindCGSToRunLoop Jan 8 02:44:44 loginwindow233: Login Window Started Security Agent Jan 8 02:44:44 WindowServer234: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Jan 8 02:44:44 com.apple.WindowServer234: Sat Jan 8 02:44:44 .local WindowServer234 <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Jan 8 02:44:54 SecurityAgent243: NSSecureTextFieldCell detected a field editor ((null)) that is not a NSTextView subclass designed to work with the cell. Ignoring... Crash report Process: loginwindow 218 Path: /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow Identifier: loginwindow Version: ??? (???) Code Type: X86-64 (Native) Parent Process: launchd [1] Date/Time: 2011-01-08 02:44:42.748 +0100 OS Version: Mac OS X 10.6.6 (10J567) Report Version: 6 Exception Type: EXC_BAD_ACCESS (SIGBUS) Exception Codes: 0x000000000000000a, 0x000000010075b000 Crashed Thread: 0 Dispatch queue: com.apple.main-thread Thread 0 Crashed: Dispatch queue: com.apple.main-thread 0 com.apple.security 0x00007fff801c6e8b Security::ReadSection::at(unsigned int) const + 25 1 com.apple.security 0x00007fff801c632f Security::DbVersion::open() + 123 2 com.apple.security 0x00007fff801c5e41 Security::DbVersion::DbVersion(Security::AppleDatabase const&, Security::RefPointer<Security::AtomicBufferedFile> const&) + 179 3 com.apple.security 0x00007fff801c594e Security::DbModifier::getDbVersion(bool) + 330 4 com.apple.security 0x00007fff801c57f5 Security::DbModifier::openDatabase() + 33 5 com.apple.security 0x00007fff801c5439 Security::Database::_dbOpen(Security::DatabaseSession&, unsigned int, Security::AccessCredentials const*, void const*) + 221 6 com.apple.security 0x00007fff801c4841 Security::DatabaseManager::dbOpen(Security::DatabaseSession&, Security::DbName const&, unsigned int, Security::AccessCredentials const*, void const*) + 77 7 com.apple.security 0x00007fff801c4723 Security::DatabaseSession::DbOpen(char const*, cssm_net_address const*, unsigned int, Security::AccessCredentials const*, void const*, long&) + 285 8 com.apple.security 0x00007fff801d8414 cssm_DbOpen(long, char const*, cssm_net_address const*, unsigned int, cssm_access_credentials const*, void const*, long*) + 108 9 com.apple.security 0x00007fff801d7fba CSSM_DL_DbOpen + 106 10 com.apple.security 0x00007fff801d62f6 Security::CssmClient::DbImpl::open() + 162 11 com.apple.security 0x00007fff801d8977 SSDatabaseImpl::open(Security::DLDbIdentifier const&) + 53 12 com.apple.security 0x00007fff801d8715 SSDLSession::DbOpen(char const*, cssm_net_address const*, unsigned int, Security::AccessCredentials const*, void const*, long&) + 263 13 com.apple.security 0x00007fff801d8414 cssm_DbOpen(long, char const*, cssm_net_address const*, unsigned int, cssm_access_credentials const*, void const*, long*) + 108 14 com.apple.security 0x00007fff801d7fba CSSM_DL_DbOpen + 106 15 com.apple.security 0x00007fff801d62f6 Security::CssmClient::DbImpl::open() + 162 16 com.apple.security 0x00007fff802fa786 Security::CssmClient::DbImpl::unlock(cssm_data const&) + 28 17 com.apple.security 0x00007fff80275b5d Security::KeychainCore::KeychainImpl::unlock(Security::CssmData const&) + 89 18 com.apple.security 0x00007fff80291a06 Security::KeychainCore::StorageManager::login(unsigned int, void const*, unsigned int, void const*) + 3336 19 com.apple.security 0x00007fff802854d3 SecKeychainLogin + 91 20 com.apple.loginwindow 0x000000010000dfc5 0x100000000 + 57285 21 com.apple.loginwindow 0x000000010000cfb4 0x100000000 + 53172 22 com.apple.Foundation 0x00007fff8721e44f __NSThreadPerformPerform + 219 23 com.apple.CoreFoundation 0x00007fff82627401 __CFRunLoopDoSources0 + 1361 24 com.apple.CoreFoundation 0x00007fff826255f9 __CFRunLoopRun + 873 25 com.apple.CoreFoundation 0x00007fff82624dbf CFRunLoopRunSpecific + 575 26 com.apple.HIToolbox 0x00007fff8444493a RunCurrentEventLoopInMode + 333 27 com.apple.HIToolbox 0x00007fff8444473f ReceiveNextEventCommon + 310 28 com.apple.HIToolbox 0x00007fff844445f8 BlockUntilNextEventMatchingListInMode + 59 29 com.apple.AppKit 0x00007fff80b01e64 _DPSNextEvent + 718 30 com.apple.AppKit 0x00007fff80b017a9 -NSApplication nextEventMatchingMask:untilDate:inMode:dequeue: + 155 31 com.apple.AppKit 0x00007fff80ac748b -NSApplication run + 395 32 com.apple.loginwindow 0x0000000100004b16 0x100000000 + 19222 33 com.apple.loginwindow 0x0000000100004580 0x100000000 + 17792 Thread 1: Dispatch queue: com.apple.libdispatch-manager 0 libSystem.B.dylib 0x00007fff8755216a kevent + 10 1 libSystem.B.dylib 0x00007fff8755403d _dispatch_mgr_invoke + 154 2 libSystem.B.dylib 0x00007fff87553d14 _dispatch_queue_invoke + 185 3 libSystem.B.dylib 0x00007fff8755383e _dispatch_worker_thread2 + 252 4 libSystem.B.dylib 0x00007fff87553168 _pthread_wqthread + 353 5 libSystem.B.dylib 0x00007fff87553005 start_wqthread + 13 Thread 0 crashed with X86 Thread State (64-bit): rax: 0x000000010075b000 rbx: 0x00007fff5fbfd990 rcx: 0x00007fff875439da rdx: 0x0000000000000000 rdi: 0x00007fff5fbfd990 rsi: 0x0000000000000000 rbp: 0x00007fff5fbfd5d0 rsp: 0x00007fff5fbfd5d0 r8: 0x0000000000000007 r9: 0x0000000000000000 r10: 0x00007fff8753beda r11: 0x0000000000000202 r12: 0x0000000100133e78 r13: 0x00007fff5fbfda50 r14: 0x00007fff5fbfda50 r15: 0x00007fff5fbfdaa0 rip: 0x00007fff801c6e8b rfl: 0x0000000000010287 cr2: 0x000000010075b000

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  • Optimizing collision engine bottleneck

    - by Vittorio Romeo
    Foreword: I'm aware that optimizing this bottleneck is not a necessity - the engine is already very fast. I, however, for fun and educational purposes, would love to find a way to make the engine even faster. I'm creating a general-purpose C++ 2D collision detection/response engine, with an emphasis on flexibility and speed. Here's a very basic diagram of its architecture: Basically, the main class is World, which owns (manages memory) of a ResolverBase*, a SpatialBase* and a vector<Body*>. SpatialBase is a pure virtual class which deals with broad-phase collision detection. ResolverBase is a pure virtual class which deals with collision resolution. The bodies communicate to the World::SpatialBase* with SpatialInfo objects, owned by the bodies themselves. There currenly is one spatial class: Grid : SpatialBase, which is a basic fixed 2D grid. It has it's own info class, GridInfo : SpatialInfo. Here's how its architecture looks: The Grid class owns a 2D array of Cell*. The Cell class contains two collection of (not owned) Body*: a vector<Body*> which contains all the bodies that are in the cell, and a map<int, vector<Body*>> which contains all the bodies that are in the cell, divided in groups. Bodies, in fact, have a groupId int that is used for collision groups. GridInfo objects also contain non-owning pointers to the cells the body is in. As I previously said, the engine is based on groups. Body::getGroups() returns a vector<int> of all the groups the body is part of. Body::getGroupsToCheck() returns a vector<int> of all the groups the body has to check collision against. Bodies can occupy more than a single cell. GridInfo always stores non-owning pointers to the occupied cells. After the bodies move, collision detection happens. We assume that all bodies are axis-aligned bounding boxes. How broad-phase collision detection works: Part 1: spatial info update For each Body body: Top-leftmost occupied cell and bottom-rightmost occupied cells are calculated. If they differ from the previous cells, body.gridInfo.cells is cleared, and filled with all the cells the body occupies (2D for loop from the top-leftmost cell to the bottom-rightmost cell). body is now guaranteed to know what cells it occupies. For a performance boost, it stores a pointer to every map<int, vector<Body*>> of every cell it occupies where the int is a group of body->getGroupsToCheck(). These pointers get stored in gridInfo->queries, which is simply a vector<map<int, vector<Body*>>*>. body is now guaranteed to have a pointer to every vector<Body*> of bodies of groups it needs to check collision against. These pointers are stored in gridInfo->queries. Part 2: actual collision checks For each Body body: body clears and fills a vector<Body*> bodiesToCheck, which contains all the bodies it needs to check against. Duplicates are avoided (bodies can belong to more than one group) by checking if bodiesToCheck already contains the body we're trying to add. const vector<Body*>& GridInfo::getBodiesToCheck() { bodiesToCheck.clear(); for(const auto& q : queries) for(const auto& b : *q) if(!contains(bodiesToCheck, b)) bodiesToCheck.push_back(b); return bodiesToCheck; } The GridInfo::getBodiesToCheck() method IS THE BOTTLENECK. The bodiesToCheck vector must be filled for every body update because bodies could have moved meanwhile. It also needs to prevent duplicate collision checks. The contains function simply checks if the vector already contains a body with std::find. Collision is checked and resolved for every body in bodiesToCheck. That's it. So, I've been trying to optimize this broad-phase collision detection for quite a while now. Every time I try something else than the current architecture/setup, something doesn't go as planned or I make assumption about the simulation that later are proven to be false. My question is: how can I optimize the broad-phase of my collision engine maintaining the grouped bodies approach? Is there some kind of magic C++ optimization that can be applied here? Can the architecture be redesigned in order to allow for more performance? Actual implementation: SSVSCollsion Body.h, Body.cpp World.h, World.cpp Grid.h, Grid.cpp Cell.h, Cell.cpp GridInfo.h, GridInfo.cpp

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  • New Whitepaper: Oracle E-Business Suite on Exadata

    - by Steven Chan
    Our Maximum Availability Architecture (MAA) team has quietly been amassing a formidable set of whitepapers about the Oracle Exadata Database Machine.  They're available here:MAA Best Practices - Exadata Database MachineIf you're one of the lucky ones with access to this hardware platform, you'll be pleased to hear that the MAA team has just published a new whitepaper with best practices for EBS environments:Oracle E-Business Suite on ExadataThis whitepaper covers the following topics:Getting to Exadata -- a high level overview of fresh installation on, and migration to, Exadata Database Machine with pointers to more detailed documentation High Availability and Disaster Recovery -- an overview of our MAA best practices with pointers to our detailed MAA Best Practices documentation Performance and Scalability -- best practices for running Oracle E-Business Suite on Exadata Database Machine based on our internal testing

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  • Linked List is now Patented?

    - by John Isaiah Carmona
    Linked list Ming-Jen Wang Patent number: 7028023 Filing date: Sep 26, 2002 Issue date: Apr 11, 2006 Application number: 10/260,471 A computerized list is provided with auxiliary pointers for traversing the list in different sequences. One or more auxiliary pointers enable a fast, sequential traversal of the list with a minimum of computational time. Such lists may be used in any application where lists may be reordered for various purposes. Does this mean that I need to acquire permission before using a linked list in my codes? What about the codes I write from my previous apps that uses a linked list? What about the framework that implements the linked list?

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  • Camera wont stay behind model after pitch, then rotation

    - by ChocoMan
    I have a camera position behind a model. Currently, if I push the left thumbstick making my model move forward, backward, or strafe, the camera stays with the model. If I push the right thumbstick left or right, the model rotates in those directions fine along with the camera rotating while maintaining its position relatively behind the model. But when I pitch the model up or down, then rotate the model afterwards, the camera moves slightly rotates in a clock-like fashion behind the model. If I do a few rotations of the model and try to pitch the camera, the camera will eventually be looking at the side, then eventually the front of the model while also rotating in a clock-like fashion. My question is, how do I keep the camera to pitch up and down behind the model no matter how much the model has rotated? Here is what I got: // Rotates model and pitches camera on its own axis public void modelRotMovement(GamePadState pController) { // Rotates Camera with model Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(angularSpeed); // Pitches Camera around model Pitch = pController.ThumbSticks.Right.Y * MathHelper.ToRadians(angularSpeed); AddRotation = Quaternion.CreateFromYawPitchRoll(Yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); } // Orbit (yaw) Camera around with model (only seeing back of model) public void cameraYaw(Vector3 axisYaw, float yaw) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisYaw, yaw)) + ModelLoad.camTarget; } // Raise camera above or below model's shoulders public void cameraPitch(Vector3 axisPitch, float pitch) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisPitch, pitch)) + ModelLoad.camTarget; } // Call in update method public void updateCamera() { cameraYaw(Vector3.Up, Yaw); cameraPitch(Vector3.Right, Pitch); } NOTE: I tried to use addPitch just like addRotation but it didn't work...

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  • C#: Handling Notifications: inheritance, events, or delegates?

    - by James Michael Hare
    Often times as developers we have to design a class where we get notification when certain things happen. In older object-oriented code this would often be implemented by overriding methods -- with events, delegates, and interfaces, however, we have far more elegant options. So, when should you use each of these methods and what are their strengths and weaknesses? Now, for the purposes of this article when I say notification, I'm just talking about ways for a class to let a user know that something has occurred. This can be through any programmatic means such as inheritance, events, delegates, etc. So let's build some context. I'm sitting here thinking about a provider neutral messaging layer for the place I work, and I got to the point where I needed to design the message subscriber which will receive messages from the message bus. Basically, what we want is to be able to create a message listener and have it be called whenever a new message arrives. Now, back before the flood we would have done this via inheritance and an abstract class: 1:  2: // using inheritance - omitting argument null checks and halt logic 3: public abstract class MessageListener 4: { 5: private ISubscriber _subscriber; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber) 11: { 12: _subscriber = subscriber; 13: _messageThread = new Thread(MessageLoop); 14: _messageThread.Start(); 15: } 16:  17: // user will override this to process their messages 18: protected abstract void OnMessageReceived(Message msg); 19:  20: // handle the looping in the thread 21: private void MessageLoop() 22: { 23: while(!_isHalted) 24: { 25: // as long as processing, wait 1 second for message 26: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 27: if(msg != null) 28: { 29: OnMessageReceived(msg); 30: } 31: } 32: } 33: ... 34: } It seems so odd to write this kind of code now. Does it feel odd to you? Maybe it's just because I've gotten so used to delegation that I really don't like the feel of this. To me it is akin to saying that if I want to drive my car I need to derive a new instance of it just to put myself in the driver's seat. And yet, unquestionably, five years ago I would have probably written the code as you see above. To me, inheritance is a flawed approach for notifications due to several reasons: Inheritance is one of the HIGHEST forms of coupling. You can't seal the listener class because it depends on sub-classing to work. Because C# does not allow multiple-inheritance, I've spent my one inheritance implementing this class. Every time you need to listen to a bus, you have to derive a class which leads to lots of trivial sub-classes. The act of consuming a message should be a separate responsibility than the act of listening for a message (SRP). Inheritance is such a strong statement (this IS-A that) that it should only be used in building type hierarchies and not for overriding use-specific behaviors and notifications. Chances are, if a class needs to be inherited to be used, it most likely is not designed as well as it could be in today's modern programming languages. So lets look at the other tools available to us for getting notified instead. Here's a few other choices to consider. Have the listener expose a MessageReceived event. Have the listener accept a new IMessageHandler interface instance. Have the listener accept an Action<Message> delegate. Really, all of these are different forms of delegation. Now, .NET events are a bit heavier than the other types of delegates in terms of run-time execution, but they are a great way to allow others using your class to subscribe to your events: 1: // using event - ommiting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private bool _isHalted = false; 6: private Thread _messageThread; 7:  8: // assign the subscriber and start the messaging loop 9: public MessageListener(ISubscriber subscriber) 10: { 11: _subscriber = subscriber; 12: _messageThread = new Thread(MessageLoop); 13: _messageThread.Start(); 14: } 15:  16: // user will override this to process their messages 17: public event Action<Message> MessageReceived; 18:  19: // handle the looping in the thread 20: private void MessageLoop() 21: { 22: while(!_isHalted) 23: { 24: // as long as processing, wait 1 second for message 25: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 26: if(msg != null && MessageReceived != null) 27: { 28: MessageReceived(msg); 29: } 30: } 31: } 32: } Note, now we can seal the class to avoid changes and the user just needs to provide a message handling method: 1: theListener.MessageReceived += CustomReceiveMethod; However, personally I don't think events hold up as well in this case because events are largely optional. To me, what is the point of a listener if you create one with no event listeners? So in my mind, use events when handling the notification is optional. So how about the delegation via interface? I personally like this method quite a bit. Basically what it does is similar to inheritance method mentioned first, but better because it makes it easy to split the part of the class that doesn't change (the base listener behavior) from the part that does change (the user-specified action after receiving a message). So assuming we had an interface like: 1: public interface IMessageHandler 2: { 3: void OnMessageReceived(Message receivedMessage); 4: } Our listener would look like this: 1: // using delegation via interface - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private IMessageHandler _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler.OnMessageReceived(msg); 28: } 29: } 30: } 31: } And they would call it by creating a class that implements IMessageHandler and pass that instance into the constructor of the listener. I like that this alleviates the issues of inheritance and essentially forces you to provide a handler (as opposed to events) on construction. Well, this is good, but personally I think we could go one step further. While I like this better than events or inheritance, it still forces you to implement a specific method name. What if that name collides? Furthermore if you have lots of these you end up either with large classes inheriting multiple interfaces to implement one method, or lots of small classes. Also, if you had one class that wanted to manage messages from two different subscribers differently, it wouldn't be able to because the interface can't be overloaded. This brings me to using delegates directly. In general, every time I think about creating an interface for something, and if that interface contains only one method, I start thinking a delegate is a better approach. Now, that said delegates don't accomplish everything an interface can. Obviously having the interface allows you to refer to the classes that implement the interface which can be very handy. In this case, though, really all you want is a method to handle the messages. So let's look at a method delegate: 1: // using delegation via delegate - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler(msg); 28: } 29: } 30: } 31: } Here the MessageListener now takes an Action<Message>.  For those of you unfamiliar with the pre-defined delegate types in .NET, that is a method with the signature: void SomeMethodName(Message). The great thing about delegates is it gives you a lot of power. You could create an anonymous delegate, a lambda, or specify any other method as long as it satisfies the Action<Message> signature. This way, you don't need to define an arbitrary helper class or name the method a specific thing. Incidentally, we could combine both the interface and delegate approach to allow maximum flexibility. Doing this, the user could either pass in a delegate, or specify a delegate interface: 1: // using delegation - give users choice of interface or delegate 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // passes the interface method as a delegate using method group 19: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 20: : this(subscriber, handler.OnMessageReceived) 21: { 22: } 23:  24: // handle the looping in the thread 25: private void MessageLoop() 26: { 27: while(!_isHalted) 28: { 29: // as long as processing, wait 1 second for message 30: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 31: if(msg != null) 32: { 33: _handler(msg); 34: } 35: } 36: } 37: } } This is the method I tend to prefer because it allows the user of the class to choose which method works best for them. You may be curious about the actual performance of these different methods. 1: Enter iterations: 2: 1000000 3:  4: Inheritance took 4 ms. 5: Events took 7 ms. 6: Interface delegation took 4 ms. 7: Lambda delegate took 5 ms. Before you get too caught up in the numbers, however, keep in mind that this is performance over over 1,000,000 iterations. Since they are all < 10 ms which boils down to fractions of a micro-second per iteration so really any of them are a fine choice performance wise. As such, I think the choice of what to do really boils down to what you're trying to do. Here's my guidelines: Inheritance should be used only when defining a collection of related types with implementation specific behaviors, it should not be used as a hook for users to add their own functionality. Events should be used when subscription is optional or multi-cast is desired. Interface delegation should be used when you wish to refer to implementing classes by the interface type or if the type requires several methods to be implemented. Delegate method delegation should be used when you only need to provide one method and do not need to refer to implementers by the interface name.

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  • Switch vs Polymorphism when dealing with model and view

    - by Raphael Oliveira
    I can't figure out a better solution to my problem. I have a view controller that presents a list of elements. Those elements are models that can be an instance of B, C, D, etc and inherit from A. So in that view controller, each item should go to a different screen of the application and pass some data when the user select one of them. The two alternatives that comes to my mind are (please ignore the syntax, it is not a specific language) 1) switch (I know that sucks) //inside the view controller void onClickItem(int index) { A a = items.get(index); switch(a.type) { case b: B b = (B)a; go to screen X; x.v1 = b.v1; // fill X with b data x.v2 = b.v2; case c: go to screen Y; etc... } } 2) polymorphism //inside the view controller void onClickItem(int index) { A a = items.get(index); Screen s = new (a.getDestinationScreen()); //ignore the syntax s.v1 = a.v1; // fill s with information about A s.v2 = a.v2; show(s); } //inside B Class getDestinationScreen(void) { return Class(X); } //inside C Class getDestinationScreen(void) { return Class(Y); } My problem with solution 2 is that since B, C, D, etc are models, they shouldn't know about view related stuff. Or should they in that case?

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  • OpenGL Tessellation makes point

    - by urza57
    A little problem with my tessellation shader. I try to implement a simple tessellation shader but it only makes points. Here's my vertex shader : out vec4 ecPosition; out vec3 ecNormal; void main( void ) { vec4 position = gl_Vertex; gl_Position = gl_ModelViewProjectionMatrix * position; ecPosition = gl_ModelViewMatrix * position; ecNormal = normalize(gl_NormalMatrix * gl_Normal); } My tessellation control shader : layout(vertices = 3) out; out vec4 ecPosition3[]; in vec3 ecNormal[]; in vec4 ecPosition[]; out vec3 myNormal[]; void main() { gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position; myNormal[gl_InvocationID] = ecNormal[gl_InvocationID]; ecPosition3[gl_InvocationID] = ecPosition[gl_InvocationID]; gl_TessLevelOuter[0] = float(4.0); gl_TessLevelOuter[1] = float(4.0); gl_TessLevelOuter[2] = float(4.0); gl_TessLevelInner[0] = float(4.0); } And my Tessellation Evaluation shader: layout(triangles, equal_spacing, ccw) in; in vec3 myNormal[]; in vec4 ecPosition3[]; out vec3 ecNormal; out vec4 ecPosition; void main() { float u = gl_TessCoord.x; float v = gl_TessCoord.y; float w = gl_TessCoord.z; vec3 position = vec4(gl_in[0].gl_Position.xyz * u + gl_in[1].gl_Position.xyz * v + gl_in[2].gl_Position.xyz * w ); vec3 position2 = vec4(ecPosition3[0].xyz * u + ecPosition3[1].xyz * v + ecPosition3[2].xyz * w ); vec3 normal = myNormal[0] * u + myNormal[1] * v + myNormal[2] * w ); ecNormal = normal; gl_Position = vec4(position, 1.0); ecPosition = vec4(position2, 1.0); } Thank you !

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  • When does the "Do One Thing" paradigm become harmful?

    - by Petr
    For the sake of argument here's a sample function that prints contents of a given file line-by-line. Version 1: void printFile(const string & filePath) { fstream file(filePath, ios::in); string line; while (file.good()) { getline(file, line); cout << line << endl; } } I know it is recommended that functions do one thing at one level of abstraction. To me, though code above does pretty much one thing and is fairly atomic. Some books (such as Robert C. Martin's Clean Code) seem to suggest breaking the above code into separate functions. Version 2: void printLine(const string & line) { cout << line << endl; } void printLines(fstream & file) { string line; while (file.good()) { getline(file, line); printLine(line); } } void printFile(const string & filePath) { fstream file(filePath, ios::in); printLines(file); } I understand what they want to achieve (open file / read lines / print line), but isn't it a bit of overkill? The original version is simple and in some sense already does one thing - prints a file. The second version will lead to a large number of really small functions which may be far less legible than the first version. Wouldn't it be, in this case, better to have the code at one place? At which point does the "Do One Thing" paradigm become harmful?

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  • Problem with Ogre::Camera lookAt function when target is directly below.

    - by PigBen
    I am trying to make a class which controls a camera. It's pretty basic right now, it looks like this: class HoveringCameraController { public: void init(Ogre::Camera & camera, AnimatedBody & target, Ogre::Real height); void update(Ogre::Real time_delta); private: Ogre::Camera * camera_; AnimatedBody * target_; Ogre::Real height_; }; HoveringCameraController.cpp void HoveringCameraController::init(Ogre::Camera & camera, AnimatedBody & target, Ogre::Real height) { camera_ = &camera; target_ = &target; height_ = height; update(0.0); } void HoveringCameraController::update(Ogre::Real time_delta) { auto position = target_->getPosition(); position.y += height_; camera_->setPosition(position); camera_->lookAt(target_->getPosition()); } AnimatedBody is just a class that encapsulates an entity, it's animations and a scene node. The getPosition function is simply forwarded to it's scene node. What I want(for now) is for the camera to simply follow the AnimatedBody overhead at the distance given(the height parameter), and look down at it. It follows the object around, but it doesn't look straight down, it's tilted quite a bit in the positive Z direction. Does anybody have any idea why it would do that? If I change this line: position.y += height_; to this: position.x += height_; or this: position.z += height_; it does exactly what I would expect. It follows the object from the side or front, and looks directly at it.

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  • Mandelbrot set not displaying properly

    - by brainydexter
    I am trying to render mandelbrot set using glsl. I'm not sure why its not rendering the correct shape. Does the mandelbrot calculation require values to be within a range for the (x,y) [ or (real, imag) ] ? Here is a screenshot: I render a quad as follows: float w2 = 6; float h2 = 5; glBegin(GL_QUADS); glVertex3f(-w2, h2, 0.0); glVertex3f(-w2, -h2, 0.0); glVertex3f(w2, -h2, 0.0); glVertex3f(w2, h2, 0.0); glEnd(); My vertex shader: varying vec3 Position; void main(void) { Position = gl_Vertex.xyz; gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } My fragment shader (where all the meat is): uniform float MAXITERATIONS; varying vec3 Position; void main (void) { float zoom = 1.0; float centerX = 0.0; float centerY = 0.0; float real = Position.x * zoom + centerX; float imag = Position.y * zoom + centerY; float r2 = 0.0; float iter; for(iter = 0.0; iter < MAXITERATIONS && r2 < 4.0; ++iter) { float tempreal = real; real = (tempreal * tempreal) + (imag * imag); imag = 2.0 * real * imag; r2 = (real * real) + (imag * imag); } vec3 color; if(r2 < 4.0) color = vec3(1.0); else color = vec3( iter / MAXITERATIONS ); gl_FragColor = vec4(color, 1.0); }

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  • How can I Implement KeyListeners/ActionListeners into the JFrame?

    - by A.K.
    I'll get to the point: I have a player in my game that you control with the keyboard yet the key methods in the player class and ActionListener w/ KeyAdapter in the Board class don't seem to fire. So far I've tried adding these key methods into the JFrame, doesn't seem to let me move him even though other objects that I have (enemies) can move fine. Here's part of the JFrame class with the event listeners: frm.addKeyListener(KeyBoardListener); public void mouseClicked(MouseEvent e) { nSound.play(); StartB.setContentAreaFilled(false); cards.remove(StartB); frm.remove(TitleL); frm.remove(cards); frm.setLayout(new GridLayout(1, 1)); frm.add(nBoard); //Add Game "Tiles" Or Content. x = 1200 nBoard.setPreferredSize(new Dimension(1200, 420)); cards.revalidate(); frm.validate(); } public KeyListener KeyBoardListener = new KeyListener() { @Override public void keyPressed(KeyEvent args0) { int key = args0.getKeyCode(); if(key == KeyEvent.VK_LEFT) { nBoard.S.vx = -4; } if(key == KeyEvent.VK_RIGHT) { nBoard.S.vx = 4; } if(key == KeyEvent.VK_UP) { nBoard.S.vy = -4; } if(key == KeyEvent.VK_DOWN) { nBoard.S.vy = 4; } if(key == KeyEvent.VK_SPACE) { nBoard.S.fire(); } } @Override public void keyReleased(KeyEvent args0) { int key = args0.getKeyCode(); if(key == KeyEvent.VK_LEFT) { nBoard.S.vx = 0; } if(key == KeyEvent.VK_RIGHT) { nBoard.S.vx = 0; } if(key == KeyEvent.VK_UP) { nBoard.S.vy = 0; } if(key == KeyEvent.VK_DOWN) { nBoard.S.vy = 0; } } @Override public void keyTyped(KeyEvent args0) { // TODO Auto-generated method stub } };

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  • Using multiple indexes with buffer objects in OpenTK

    - by Rushyo
    I've got multiple buffers in OpenGL holding data on position, normals and texcoords. I also have an equal number of buffers holding distinct index data for each of those buffers. I quite like this format (indvidual indexes for each buffer) utilised by COLLADA since it strikes me as optimally efficient at accessing each buffer. I've set up pointers to the relevant data arrays using VertexPointer, NormalPointer, etc however I have no way to assign pointers to the index buffers since DrawElements appear to only look at one ElementArrayBuffer. Can I utilise multiple indices some way or will I be better off using a different technique which can support this? I'd prefer to keep the distinct indices if at all possible.

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  • Java applet game design no keyboard focus

    - by Sri Harsha Chilakapati
    THIS IS PROBABLY THE WRONG PLACE. POSTED ITHERE (STACKOVERFLOW) I'm making an applet game and it is rendering, the game loop is running, the animations are updating, but the keyboard input is not working. Here's an SSCCE. public class Game extends JApplet implements Runnable { public void init(){ // Initialize the game when called by browser setFocusable(true); requestFocus(); requestFocusInWindow(); // Always returning false GInput.install(this); // Install the input manager for this class new Thread(this).start(); } public void run(){ startGameLoop(); } } And Here's the GInput class. public class GInput implements KeyListener { public static void install(Component c){ new GInput(c); } public GInput(Component c){ c.addKeyListener(this); } public void keyPressed(KeyEvent e){ System.out.println("A key has been pressed"); } ...... } This is my GInput class. When run as an applet, it doesn't work and when I add the Game class to a frame, it works properly. Thanks

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  • What are some good resources for learning about file systems? [closed]

    - by Daniel
    I'd like to learn about file system design at a very detailed level. I'm currently in a graduate level operating systems course, and we're currently going over file systems. We mostly discuss papers and such, but our semester long project is to implement a log-structured file system using fuse and a virtual disk. Are there any good books that focus heavily on file system design and implementation? I have some conceptual clouding on things that seem very basic such as "when we say that an inode has pointers to blocks, do we mean anything besides the inode keeping track of block numbers? Is there any other format for 'disk pointers'?" I'm actually looking at file system design to start my career, so I'm probably going to try to implement a more traditional file system with fuse and our virtual disk format after this course is over.

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  • Memory Management/Embedded Management in C

    - by Sauron
    Im wondering if there is a set or a few good books/Tutorials/Etc.. that go into Memory Management/Allocation Specifically (or at least have a good dedicated section to it) when it comes to C. This is more for me learning Embedded and trying to keep Size down. I've read and Learned C fine, and the "standard" Learning books. However most of the books don't spend a huge amount of time (Understandably since C is pretty huge in general) going into the Finer details about whats going on Down Under. I saw a few on Amazon: http://www.amazon.com/C-Pointers-Dynamic-Memory-Management/dp/0471561525 http://www.amazon.com/Understanding-Pointers-C-Yashavant-Kanetkar/dp/8176563587/ref=pd_sim_b_1 (Not sure how relevant this would be) A specific Book for Embedded that has to do with this would be nice. But Code Samples or...Heck tutorials or anything about this topic would be helpful!

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  • How do I implement SkyBox in xna 4.0 Reach Profile (for Windows Phone 7)?

    - by Biny
    I'm trying to Implement SkyBox in my phone game. Most of the samples in the web are for HiDef profile, and they are using custom effects (that not supported on Windows Phone). I've tried to follow this guide. But for some reason my SkyBox is not rendered. This is my SkyBox class: using System; using System.Collections.Generic; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; using Rocuna.Core; using Rocuna.GameEngine.Graphics; using Rocuna.GameEngine.Graphics.Components; namespace Rocuna.GameEngine.Extension.WP7.Graphics { /// <summary> /// Sky box element for phone games. /// </summary> public class SkyBox : SkyBoxBase { /// <summary> /// Initializes a new instance of the <see cref="SkyBoxBase"/> class. /// </summary> /// <param name="game">The Game that the game component should be attached to.</param> public SkyBox(TextureCube cube, Game game) : base(game) { Cube = cube; CubeFaces = new Texture2D[6]; PositionOffset = new Vector3(20, 20, 20); CreateGraphic(512); StripTexturesFromCube(); InitializeData(Game.GraphicsDevice); } #region Properties /// <summary> /// Gets or sets the position offset. /// </summary> /// <value> /// The position offset. /// </value> public Vector3 PositionOffset { get; set; } /// <summary> /// Gets or sets the position. /// </summary> /// <value> /// The position. /// </value> public Vector3 Position { get; set; } /// <summary> /// Gets or sets the cube. /// </summary> /// <value> /// The cube. /// </value> public TextureCube Cube { get; set; } /// <summary> /// Gets or sets the pixel array. /// </summary> /// <value> /// The pixel array. /// </value> public Color[] PixelArray { get; set; } /// <summary> /// Gets or sets the cube faces. /// </summary> /// <value> /// The cube faces. /// </value> public Texture2D[] CubeFaces { get; set; } /// <summary> /// Gets or sets the vertex buffer. /// </summary> /// <value> /// The vertex buffer. /// </value> public VertexBuffer VertexBuffer { get; set; } /// <summary> /// Gets or sets the index buffer. /// </summary> /// <value> /// The index buffer. /// </value> public IndexBuffer IndexBuffer { get; set; } /// <summary> /// Gets or sets the effect. /// </summary> /// <value> /// The effect. /// </value> public BasicEffect Effect { get; set; } #endregion protected override void LoadContent() { } public override void Update(GameTime gameTime) { var camera = Game.GetService<GraphicManager>().CurrentCamera; this.Position = camera.Position + PositionOffset; base.Update(gameTime); } public override void Draw(GameTime gameTime) { DrawOrder = int.MaxValue; var graphics = Effect.GraphicsDevice; graphics.DepthStencilState = new DepthStencilState() { DepthBufferEnable = false }; graphics.RasterizerState = new RasterizerState() { CullMode = CullMode.None }; graphics.BlendState = new BlendState(); graphics.SamplerStates[0] = SamplerState.AnisotropicClamp; graphics.SetVertexBuffer(VertexBuffer); graphics.Indices = IndexBuffer; Effect.Texture = CubeFaces[0]; Effect.CurrentTechnique.Passes[0].Apply(); graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, _vertices.Count, 0, 2); Effect.Texture = CubeFaces[1]; Effect.CurrentTechnique.Passes[0].Apply(); graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, _vertices.Count, 6, 2); Effect.Texture = CubeFaces[2]; Effect.CurrentTechnique.Passes[0].Apply(); graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, _vertices.Count, 12, 2); Effect.Texture = CubeFaces[3]; Effect.CurrentTechnique.Passes[0].Apply(); graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, _vertices.Count, 18, 2); Effect.Texture = CubeFaces[4]; Effect.CurrentTechnique.Passes[0].Apply(); graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, _vertices.Count, 24, 2); Effect.Texture = CubeFaces[5]; Effect.CurrentTechnique.Passes[0].Apply(); graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, _vertices.Count, 30, 2); base.Draw(gameTime); } #region Fields private List<VertexPositionNormalTexture> _vertices = new List<VertexPositionNormalTexture>(); private List<ushort> _indices = new List<ushort>(); #endregion #region Private methods private void InitializeData(GraphicsDevice graphicsDevice) { VertexBuffer = new VertexBuffer(graphicsDevice, typeof(VertexPositionNormalTexture), _vertices.Count, BufferUsage.None); VertexBuffer.SetData<VertexPositionNormalTexture>(_vertices.ToArray()); // Create an index buffer, and copy our index data into it. IndexBuffer = new IndexBuffer(graphicsDevice, typeof(ushort), _indices.Count, BufferUsage.None); IndexBuffer.SetData<ushort>(_indices.ToArray()); // Create a BasicEffect, which will be used to render the primitive. Effect = new BasicEffect(graphicsDevice); Effect.TextureEnabled = true; Effect.EnableDefaultLighting(); } private void CreateGraphic(float size) { Vector3[] normals = { Vector3.Right, Vector3.Left, Vector3.Up, Vector3.Down, Vector3.Backward, Vector3.Forward, }; Vector2[] textureCoordinates = { Vector2.One, Vector2.UnitY, Vector2.Zero, Vector2.UnitX, Vector2.Zero, Vector2.UnitX, Vector2.One, Vector2.UnitY, Vector2.Zero, Vector2.UnitX, Vector2.One, Vector2.UnitY, Vector2.Zero, Vector2.UnitX, Vector2.One, Vector2.UnitY, Vector2.UnitY, Vector2.Zero, Vector2.UnitX, Vector2.One, Vector2.UnitY, Vector2.Zero, Vector2.UnitX, Vector2.One, }; var index = 0; foreach (var normal in normals) { var side1 = new Vector3(normal.Z, normal.X, normal.Y); var side2 = Vector3.Cross(normal, side1); AddIndex(CurrentVertex + 0); AddIndex(CurrentVertex + 1); AddIndex(CurrentVertex + 2); AddIndex(CurrentVertex + 0); AddIndex(CurrentVertex + 2); AddIndex(CurrentVertex + 3); AddVertex((normal - side1 - side2) * size / 2, normal, textureCoordinates[index++]); AddVertex((normal - side1 + side2) * size / 2, normal, textureCoordinates[index++]); AddVertex((normal + side1 + side2) * size / 2, normal, textureCoordinates[index++]); AddVertex((normal + side1 - side2) * size / 2, normal, textureCoordinates[index++]); } } protected void StripTexturesFromCube() { PixelArray = new Color[Cube.Size * Cube.Size]; for (int s = 0; s < CubeFaces.Length; s++) { CubeFaces[s] = new Texture2D(Game.GraphicsDevice, Cube.Size, Cube.Size, false, SurfaceFormat.Color); switch (s) { case 0: Cube.GetData<Color>(CubeMapFace.PositiveX, PixelArray); CubeFaces[s].SetData<Color>(PixelArray); break; case 1: Cube.GetData(CubeMapFace.NegativeX, PixelArray); CubeFaces[s].SetData(PixelArray); break; case 2: Cube.GetData(CubeMapFace.PositiveY, PixelArray); CubeFaces[s].SetData(PixelArray); break; case 3: Cube.GetData(CubeMapFace.NegativeY, PixelArray); CubeFaces[s].SetData(PixelArray); break; case 4: Cube.GetData(CubeMapFace.PositiveZ, PixelArray); CubeFaces[s].SetData(PixelArray); break; case 5: Cube.GetData(CubeMapFace.NegativeZ, PixelArray); CubeFaces[s].SetData(PixelArray); break; } } } protected void AddVertex(Vector3 position, Vector3 normal, Vector2 textureCoordinates) { _vertices.Add(new VertexPositionNormalTexture(position, normal, textureCoordinates)); } protected void AddIndex(int index) { if (index > ushort.MaxValue) throw new ArgumentOutOfRangeException("index"); _indices.Add((ushort)index); } protected int CurrentVertex { get { return _vertices.Count; } } #endregion } }

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  • Why is a linked list implementation considered linear?

    - by VeeKay
    My apologies for asking such a simple question. Instead of posting such basic question in SO, I felt that this is more apt a question here. I tried finding an answer for this but none of them are logically appealing or convincing to my understanding. Typically, computer memory is always linear. So is the term non linear used for a data structure in a logical sense? If so, to logically achieve non linearity in a linear computer memory, we use pointers. Right? In that case, if pointers are virtual implementations for achieving non linearity, Why would a data structure like linked list be considered linear if in reality the nodes are never physically adjacent?

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  • Using runtime generic type reflection to build a smarter DAO

    - by kerry
    Have you ever wished you could get the runtime type of your generic class? I wonder why they didn’t put this in the language. It is possible, however, with reflection: Consider a data access object (DAO) (note: I had to use brackets b/c the arrows were messing with wordpress): public interface Identifiable { public Long getId(); } public interface Dao { public T findById(Long id); public void save(T obj); public void delete(T obj); } Using reflection, we can create a DAO implementation base class, HibernateDao, that will work for any object: import java.lang.reflect.Field; import java.lang.reflect.ParameterizedType; public class HibernateDao implements Dao { private final Class clazz; public HibernateDao(Session session) { // the magic ParameterizedType parameterizedType = (ParameterizedType) clazz.getGenericSuperclass(); return (Class) parameterizedType.getActualTypeArguments()[0]; } public T findById(Long id) { return session.get(clazz, id); } public void save(T obj) { session.saveOrUpdate(obj); } public void delete(T obj) { session.delete(obj); } } Then, all we have to do is extend from the class: public class BookDaoHibernateImpl extends HibernateDao { }

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  • Motivation and use of move constructors in C++

    - by Giorgio
    I recently have been reading about move constructors in C++ (see e.g. here) and I am trying to understand how they work and when I should use them. As far as I understand, a move constructor is used to alleviate the performance problems caused by copying large objects. The wikipedia page says: "A chronic performance problem with C++03 is the costly and unnecessary deep copies that can happen implicitly when objects are passed by value." I normally address such situations by passing the objects by reference, or by using smart pointers (e.g. boost::shared_ptr) to pass around the object (the smart pointers get copied instead of the object). What are the situations in which the above two techniques are not sufficient and using a move constructor is more convenient?

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  • How do I separate codes with classes?

    - by Trycon
    I have this main class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.SlickException; import org.newdawn.slick.state.BasicGameState; import org.newdawn.slick.state.StateBasedGame; public class tests extends BasicGameState{ public boolean render=false; tests1 test = new tests1(); public tests(int test) { // TODO Auto-generated constructor stub } @Override public void init(GameContainer arg0, StateBasedGame arg1) throws SlickException { // TODO Auto-generated method stub } @Override public void render(GameContainer arg0, StateBasedGame arg1, Graphics g) throws SlickException { // TODO Auto-generated method stub if(render==true) { g.drawString("Hello",100,100); } } @Override public void update(GameContainer gc, StateBasedGame s, int delta) throws SlickException { // TODO Auto-generated method stub test.render=render; test.update(gc, s, delta); } @Override public int getID() { // TODO Auto-generated method stub return 1000; } } and its sub-class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Input; import org.newdawn.slick.state.StateBasedGame; public class tests1 { public boolean render; public void update(GameContainer gc, StateBasedGame s, int delta) { Input input = gc.getInput(); if(input.isKeyPressed(Input.KEY_X)) { render=true; } } } I was finding a way to prevent many codes in one class. I'm new to java. When I try running my game, then when I press X, it does not work. How am I suppose to fix that?

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  • SQL 2014 does data the way developers want

    - by Rob Farley
    A post I’ve been meaning to write for a while, good that it fits with this month’s T-SQL Tuesday, hosted by Joey D’Antoni (@jdanton) Ever since I got into databases, I’ve been a fan. I studied Pure Maths at university (as well as Computer Science), and am very comfortable with Set Theory, which undergirds relational database concepts. But I’ve also spent a long time as a developer, and appreciate that that databases don’t exactly fit within the stuff I learned in my first year of uni, particularly the “Algorithms and Data Structures” subject, in which we studied concepts like linked lists. Writing in languages like C, we used pointers to quickly move around data, without a database in sight. Of course, if we had a power failure all this data was lost, as it was only persisted in RAM. Perhaps it’s why I’m a fan of database internals, of indexes, latches, execution plans, and so on – the developer in me wants to be reassured that we’re getting to the data as efficiently as possible. Back when SQL Server 2005 was approaching, one of the big stories was around CLR. Many were saying that T-SQL stored procedures would be a thing of the past because we now had CLR, and that obviously going to be much faster than using the abstracted T-SQL. Around the same time, we were seeing technologies like Linq-to-SQL produce poor T-SQL equivalents, and developers had had a gutful. They wanted to move away from T-SQL, having lost trust in it. I was never one of those developers, because I’d looked under the covers and knew that despite being abstracted, T-SQL was still a good way of getting to data. It worked for me, appealing to both my Set Theory side and my Developer side. CLR hasn’t exactly become the default option for stored procedures, although there are plenty of situations where it can be useful for getting faster performance. SQL Server 2014 is different though, through Hekaton – its In-Memory OLTP environment. When you create a table using Hekaton (that is, a memory-optimized one), the table you create is the kind of thing you’d’ve made as a developer. It creates code in C leveraging structs and pointers and arrays, which it compiles into fast code. When you insert data into it, it creates a new instance of a struct in memory, and adds it to an array. When the insert is committed, a small write is made to the transaction to make sure it’s durable, but none of the locking and latching behaviour that typifies transactional systems is needed. Indexes are done using hashes and using bw-trees (which avoid locking through the use of pointers) and by handling each updates as a delete-and-insert. This is data the way that developers do it when they’re coding for performance – the way I was taught at university before I learned about databases. Being done in C, it compiles to very quick code, and although these tables don’t support every feature that regular SQL tables do, this is still an excellent direction that has been taken. @rob_farley

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  • Flixel: doesn't light tile up

    - by Arno
    i'm creating a game with flixel, and I want to have a effect when you mouse over a tile, I tried implementing it, and this is what it gives: public class GameState extends FlxState { private var block:EmptyBlock; public function GameState() { } override public function create():void { for (var i:Number = 0; i < 30; i++) { block = new EmptyBlock(i, 20); block.create(); } } override public function update():void { block.update(); super.update(); } } } GameState class and here is the EmptyBlock class: public class EmptyBlock { private var x:int; private var y:int; private var row:FlxRect public function EmptyBlock(x:int, y:int ) { this.x = x; this.y = y; } public function create():void { row = new FlxRect(x, y, 32, 32); trace ("Created block at" + x + y); } public function update():void { if (FlxG.mouse.screenX == row.x) { if (FlxG.mouse.screenY == row.y) { var outline:FlxSprite = new FlxSprite(row.x, row.y).makeGraphic(row.width, row.height, 0x002525); } } } } }

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