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  • C#: How to resolve this circular dependency?

    - by Rosarch
    I have a circular dependency in my code, and I'm not sure how to resolve it. I am developing a game. A NPC has three components, responsible for thinking, sensing, and acting. These components need access to the NPC controller to get access to its model, but the controller needs these components to do anything. Thus, both take each other as arguments in their constructors. ISenseNPC sense = new DefaultSenseNPC(controller, worldQueryEngine); IThinkNPC think = new DefaultThinkNPC(sense); IActNPC act = new DefaultActNPC(combatEngine, sense, controller); controller = new ControllerNPC(act, think); (The above example has the parameter simplified a bit.) Without act and think, controller can't do anything, so I don't want to allow it to be initialized without them. The reverse is basically true as well. What should I do? ControllerNPC using think and act to update its state in the world: public class ControllerNPC { // ... public override void Update(long tick) { // ... act.UpdateFromBehavior(CurrentBehavior, tick); CurrentBehavior = think.TransitionState(CurrentBehavior, tick); } // ... } DefaultSenseNPC using controller to determine if it's colliding with anything: public class DefaultSenseNPC { // ... public bool IsCollidingWithTarget() { return worldQuery.IsColliding(controller, model.Target); } // ... }

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  • Circular Dependencies in XML file

    - by user3006081
    my android xml layout file keeps on Exception raised during rendering: Circular dependencies cannot exist in RelativeLayout Exception details are logged in Window Show View Error Log I cant figure out why? here is my code <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.amandhapola.ribbit.LoginActivity" android:background="@drawable/background_fill" > <ImageView android:id="@+id/backgroundImage" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_alignParentLeft="true" android:layout_alignParentTop="true" android:scaleType="fitStart" android:src="@drawable/background" android:contentDescription="@string/content_desc_background"/> <TextView android:id="@+id/title" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:layout_above="@+id/subtitle" android:layout_centerHorizontal="true" android:textSize="60sp" android:layout_marginTop="32dp" android:textColor="@android:color/white" android:textStyle="bold" android:text="@string/app_name" /> <TextView android:id="@+id/subtitle" android:layout_centerHorizontal="true" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/title" android:layout_above="@+id/usernameField" android:textSize="13sp" android:textColor="@android:color/white" android:textStyle="bold" android:text="@string/subtitle"/> <EditText android:id="@+id/usernameField" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_above="@+id/passwordField" android:layout_below="@+id/subtitle" android:layout_alignParentLeft="true" android:ems="10" android:hint="@string/username_hint" /> <EditText android:id="@+id/passwordField" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@+id/usernameField" android:layout_above="@+id/loginButton" android:layout_alignParentLeft="true" android:layout_marginBottom="43dp" android:ems="10" android:hint="@string/password_hint" android:inputType="textPassword" /> <Button android:id="@+id/loginButton" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@+id/passwordField" android:layout_above="@+id/signUpText" android:layout_alignParentLeft="true" android:text="@string/login_button_label" /> <TextView android:id="@+id/signUpText" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="12dp" android:layout_centerHorizontal="true" android:textColor="@android:color/white" android:layout_below="@+id/loginButton" android:text="@string/sign_up_text" /> </RelativeLayout>

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  • Circular dependecy in winforms app using Castle Windsor

    - by Sven
    Hello, I was experimenting a little bit with Castle winforms in a winforms project. I wanted to register all my form dependencies with Castle windsor. This way I would have a single instance for all my forms. Now I have some problem though. I'm in a situation that form x has a dependency on form y and form y has a dependency on form x. Practical example maybe: form x is used to create an order, form y is the screen that has a list of customers. From form x there is a button to select a customer for the order. This will open form y where ou can search the customer. There is a button that lets you add the found customer to the order. It will call a method on form x and passes the selected customer object. I could do this with events. Raise an event in form y and listen for that in form x. But isn't there a way around the circular dependency in Castle Windsor, lazy registration or something? Can anyone help me out? Thanks in advance

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  • jCarousel - achieving an active state AND wrap:circular

    - by swisstony
    Hey folks A while back I implemented the jCarousel image solution for a client that required a numbered active state. After a bit of googling a found the answer but noticed that the preferred circular option would not work. What would happen is that once the carousel had cycled through all its (5) images, upon the return to the first, the active state would be lost, because, according to jcarousel it was actually the 6th (the index just keeps on incrementing). I just went ahead and instead used wrap:'both' which at least had a correctly functioning active state. However now the client says they dont like this effect and simply want the animation to return to position 1 after the final image. This means I need to get'wrap: 'both' working somehow. Below is my current code. Can someone please solve this one, as its a little above my head! function highlight(carousel, obejctli,liindex,listate){ jQuery('.jcarousel-control a:nth-child('+ liindex +')').attr("class","active"); }; function removehighlight(carousel, obejctli,liindex,listate){ jQuery('.jcarousel-control a:nth-child('+ liindex +')').removeAttr("class","active"); }; jQuery('#mycarousel').jcarousel({ initCallback: mycarousel_initCallback, auto: 5, wrap: 'both', vertical: true, scroll: 1, buttonNextHTML: null, buttonPrevHTML: null, animation: 1000, itemVisibleInCallback: highlight, itemVisibleOutCallback: removehighlight }); }); Thanks in advance

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  • Json.Net Issues: StackOverflowException is thrown when serialising circular dependent ISerializable object with ReferenceLoopHandling.Ignore

    - by keyr
    I have a legacy application that used binary serialisation to persist the data. Now we wanted to use Json.net 4.5 to serialise the data without much changes to the existing classes. Things were working nice till we hit a circular dependent class. Is there any workaround to solve this problem? Sample code as shown below [Serializable] class Department : ISerializable { public Employee Manager { get; set; } public string Name { get; set; } public Department() { } public Department( SerializationInfo info, StreamingContext context ) { Manager = ( Employee )info.GetValue( "Manager", typeof( Employee ) ); Name = ( string )info.GetValue( "Name", typeof( string ) ); } public void GetObjectData( SerializationInfo info, StreamingContext context ) { info.AddValue( "Manager", Manager ); info.AddValue( "Name", Name ); } } [Serializable] class Employee : ISerializable { [NonSerialized] //This does not work [XmlIgnore]//This does not work private Department mDepartment; public Department Department { get { return mDepartment; } set { mDepartment = value; } } public string Name { get; set; } public Employee() { } public Employee( SerializationInfo info, StreamingContext context ) { Department = ( Department )info.GetValue( "Department", typeof( Department ) ); Name = ( string )info.GetValue( "Name", typeof( string ) ); } public void GetObjectData( SerializationInfo info, StreamingContext context ) { info.AddValue( "Department", Department ); info.AddValue( "Name", Name ); } } And the test code Department department = new Department(); department.Name = "Dept1"; Employee emp1 = new Employee { Name = "Emp1", Department = department }; department.Manager = emp1; Employee emp2 = new Employee() { Name = "Emp2", Department = department }; IList<Employee> employees = new List<Employee>(); employees.Add( emp1 ); employees.Add( emp2 ); var memoryStream = new MemoryStream(); var formatter = new BinaryFormatter(); formatter.Serialize( memoryStream, employees ); memoryStream.Seek( 0, SeekOrigin.Begin ); IList<Employee> deserialisedEmployees = formatter.Deserialize( memoryStream ) as IList<Employee>; //Works nicely JsonSerializerSettings jsonSS= new JsonSerializerSettings(); jsonSS.TypeNameHandling = TypeNameHandling.Objects; jsonSS.TypeNameAssemblyFormat = FormatterAssemblyStyle.Full; jsonSS.Formatting = Formatting.Indented; jsonSS.ReferenceLoopHandling = ReferenceLoopHandling.Ignore; //This is not working!! //jsonSS.ReferenceLoopHandling = ReferenceLoopHandling.Serialize; //This is also not working!! jsonSS.PreserveReferencesHandling = PreserveReferencesHandling.All; string jsonAll = JsonConvert.SerializeObject( employees, jsonSS ); //Throws stackoverflow exception Edit1: The issue has been reported to Json (http://json.codeplex.com/workitem/23668)

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  • Crop circular or elliptical image from original UIImage

    - by vikas ojha
    I am working on openCV for detecting the face .I want face to get cropped once its detected.Till now I got the face and have marked the rect/ellipse around it on iPhone. Please help me out in cropping the face in circular/elliptical pattern (UIImage *) opencvFaceDetect:(UIImage *)originalImage { cvSetErrMode(CV_ErrModeParent); IplImage *image = [self CreateIplImageFromUIImage:originalImage]; // Scaling down /* Creates IPL image (header and data) ----------------cvCreateImage CVAPI(IplImage*) cvCreateImage( CvSize size, int depth, int channels ); */ IplImage *small_image = cvCreateImage(cvSize(image->width/2,image->height/2), IPL_DEPTH_8U, 3); /*SMOOTHES DOWN THYE GUASSIAN SURFACE--------:cvPyrDown*/ cvPyrDown(image, small_image, CV_GAUSSIAN_5x5); int scale = 2; // Load XML NSString *path = [[NSBundle mainBundle] pathForResource:@"haarcascade_frontalface_default" ofType:@"xml"]; CvHaarClassifierCascade* cascade = (CvHaarClassifierCascade*)cvLoad([path cStringUsingEncoding:NSASCIIStringEncoding], NULL, NULL, NULL); // Check whether the cascade has loaded successfully. Else report and error and quit if( !cascade ) { NSLog(@"ERROR: Could not load classifier cascade\n"); //return; } //Allocate the Memory storage CvMemStorage* storage = cvCreateMemStorage(0); // Clear the memory storage which was used before cvClearMemStorage( storage ); CGColorSpaceRef colorSpace; CGContextRef contextRef; CGRect face_rect; // Find whether the cascade is loaded, to find the faces. If yes, then: if( cascade ) { CvSeq* faces = cvHaarDetectObjects(small_image, cascade, storage, 1.1f, 3, 0, cvSize(20, 20)); cvReleaseImage(&small_image); // Create canvas to show the results CGImageRef imageRef = originalImage.CGImage; colorSpace = CGColorSpaceCreateDeviceRGB(); contextRef = CGBitmapContextCreate(NULL, originalImage.size.width, originalImage.size.height, 8, originalImage.size.width * 4, colorSpace, kCGImageAlphaPremultipliedLast|kCGBitmapByteOrderDefault); //VIKAS CGContextDrawImage(contextRef, CGRectMake(0, 0, originalImage.size.width, originalImage.size.height), imageRef); CGContextSetLineWidth(contextRef, 4); CGContextSetRGBStrokeColor(contextRef, 1.0, 1.0, 1.0, 0.5); // Draw results on the iamge:Draw all components of face in the form of small rectangles // Loop the number of faces found. for(int i = 0; i < faces->total; i++) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; // Calc the rect of faces // Create a new rectangle for drawing the face CvRect cvrect = *(CvRect*)cvGetSeqElem(faces, i); // CGRect face_rect = CGContextConvertRectToDeviceSpace(contextRef, // CGRectMake(cvrect.x * scale, cvrect.y * scale, cvrect.width * scale, cvrect.height * scale)); face_rect = CGContextConvertRectToDeviceSpace(contextRef, CGRectMake(cvrect.x*scale, cvrect.y , cvrect.width*scale , cvrect.height*scale*1.25 )); facedetectapp=(FaceDetectAppDelegate *)[[UIApplication sharedApplication]delegate]; facedetectapp.grabcropcoordrect=face_rect; NSLog(@" FACE off %f %f %f %f",facedetectapp.grabcropcoordrect.origin.x,facedetectapp.grabcropcoordrect.origin.y,facedetectapp.grabcropcoordrect.size.width,facedetectapp.grabcropcoordrect.size.height); CGContextStrokeRect(contextRef, face_rect); //CGContextFillEllipseInRect(contextRef,face_rect); CGContextStrokeEllipseInRect(contextRef,face_rect); [pool release]; } } CGImageRef imageRef = CGImageCreateWithImageInRect([originalImage CGImage],face_rect); UIImage *returnImage = [UIImage imageWithCGImage:imageRef]; CGImageRelease(imageRef); CGContextRelease(contextRef); CGColorSpaceRelease(colorSpace); cvReleaseMemStorage(&storage); cvReleaseHaarClassifierCascade(&cascade); return returnImage; } } Thanks Vikas

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  • How common are circular references? Would reference-counting GC work just fine?

    - by user9521
    How common are circular references? The less common they are, the fewer hard cases you have if you are writing in a language with only reference counting-GC. Are there any cases where it wouldn't work well to make one of the references a "weak" reference so that reference counting still works? It seems like you should be able to have a language only use reference counting and weak references and have things work just fine most of the time, with the goal of efficiency. You could also have tools to help you detect memory leaks caused by circular references. Thoughts, anyone? It seems that Python uses references counting (I don't know if it uses a tracing collector occasionally or not for sure) and I know that Vala uses reference counting with weak references; I know that it's been done before, but how well would it work?

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  • How to avoid circular dependencies between Player and World?

    - by futlib
    I'm working on a 2D game where you can move up, down, left and right. I have essentially two game logic objects: Player: Has a position relative to the world World: Draws the map and the player So far, World depends on Player (i.e. has a reference to it), needing its position to figure out where to draw the player character, and which portion of the map to draw. Now I want to add collision detection to make it impossible for the player to move through walls. The simplest way I can think of is to have the Player ask the World if the intended movement is possible. But that would introduce a circular dependency between Player and World (i.e. each holds a reference to the other), which seems worth avoiding. The only way I came up with is to have the World move the Player, but I find that somewhat unintuitive. What is my best option? Or is avoiding a circular dependency not worth it?

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  • How to avoid circular relationship in SQL-Server?

    - by Shimmy
    I am creating a self-related table: Table Item columns: ItemId int - PK; Amount money - not null; Price money - a computed column using a UDF that retrieves value according to the items ancestors' Amount. ParentItemId int - nullable, reference to another ItemId in this table. I need to avoid a loop, meaning, a sibling cannot become an ancestor of his ancestors, meaning, if ItemId=2 ParentItemId = 1, then ItemId 1 ParentItemId = 2 shouldn't be allowed. I don't know what should be the best practice in this situation. I think I should add a CK that gets a Scalar value from a UDF or whatever else. EDIT: Another option is to create an INSTEAD OF trigger and put in 1 transaction the update of the ParentItemId field and selecting the Price field from the @@RowIdentity, if it fails cancel transaction, but I would prefer a UDF validating. Any ideas are sincerely welcomed.

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  • Regex for circular replacement

    - by polygenelubricants
    How would you use regex to write functions to do the following: Replace lowercase 'a' with uppercase and vice versa Where words are separated by whitespaces and > and < are special markers, replace >word with word< and vice versa Replace postincrement (i++;) with preincrement (++i;) and vice versa. Variable names are [a-z]+. Input is just a bunch of these statements. Bonus: also do decrement. Also interested in solutions in other flavors. Note: this is NOT a homework question. See also my previous explorations of regex: Regex split into overlapping strings (Alan Moore's answer is especially instructive) Can you use zero-width matching regex in String split? (my solution exploits a known Java regex bug with regards to non-obvious length lookbehind!)

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  • Circular Dependency of Navigation Control in iPhone

    - by Taimur Hamza
    Hi everyone , In my view this is one of the strangest problem i have ever come across in iPhone app development. Let me explain the scenario , i have main screen 'A' on which i have a Button that directs me to another Screen say 'B'. Now on Screen 'B' i have a feature in which user can send a mail to his friend for promotion purpose e.g a user wishes to tell a frnd about this app so i used MFMailComposeViewController and a view is generated where the user types the address and click send ( subject and body of mail is automatically generated ). After sending the mail a new view opens say screen 'C' and here i want to give the user the options . 1. Go to Screen 'A' ( which is main screen of the app ) 2. Go back to Screen 'B' ( from where the user requested to send a mail to his frnd ). Now the strange part i cannot declare the variables ( Screen 'A' and 'B' ) of both these files here at in header file of screen 'C' . Even when i declare the header file at the top it generates an error. The variables can be easily be declared and used for other screens but not for these 2 screens. Can anybody please explain wats the problem.? this the text of the error "/Users/admin/Documents/AppName/Classes/A.h:42: error: expected specifier-qualifier-list before 'B'" Thanks Guys ! Taimur

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  • How to avoid game rendering component circular references?

    - by CodexArcanum
    I'm working on a simple game design, and I wanted to break up my game objects into more reusable components. But I'm getting stuck on how exactly to implement the design I have in mind. Here's an example: I have a Logger object, whose job is simply to store a list of messages and render them to screen. You know, logging. Originally the Logger just held the list, and the game loop rendered it's contents. Then I moved the rendering logic into the Logger.Draw() method, and now I want to move it further into a LoggerRenderer object. In effect, I want to have the game loop call RenderAll, which will then call Logger.Render, which will in turn call the LoggerRenderer.Render and finally output the text. So the Logger needs to contain a Renderer object, but the Renderer needs access to the Logger's state (the message queue) in order to render. How do I resolve that? Should I be passing in the message queue and other state information explicitly to the Render method? Or should the game loop be calling the Renderer directly and it links back to the logger, but the RenderAll method never actually sees the logger object itself? This feels kind of like Command pattern, but I'm botching it up terribly.

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  • Using Guice with circular dependencies

    - by Yury Litvinov
    Consider this simple example. Class A { B b; A() { this.b = new B(this); } } In this example instance A knows about instance B, and instance B knows about instance A. My question is: how to instantiate instance A with Guice, i.e. how to make Guice take care of this complex circle dependencies?

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  • Problem determining how to order F# types due to circular references

    - by James Black
    I have some types that extend a common type, and these are my models. I then have DAO types for each model type for CRUD operations. I now have a need for a function that will allow me to find an id given any model type, so I created a new type for some miscellaneous functions. The problem is that I don't know how to order these types. Currently I have models before dao, but I somehow need DAOMisc before CityDAO and CityDAO before DAOMisc, which isn't possible. The simple approach would be to put this function in each DAO, referring to just the types that can come before it, so, State comes before City as State has a foreign key relationship with City, so the miscellaneous function would be very short. But, this just strikes me as wrong, so I am not certain how to best approach this. Here is my miscellaneous type, where BaseType is a common type for all my models. type DAOMisc = member internal self.FindIdByType item = match(item:BaseType) with | :? StateType as i -> let a = (StateDAO()).Retrieve i a.Head.Id | :? CityType as i -> let a = (CityDAO()).Retrieve i a.Head.Id | _ -> -1 Here is one dao type. CommonDAO actually has the code for the CRUD operations, but that is not important here. type CityDAO() = inherit CommonDAO<CityType>("city", ["name"; "state_id"], (fun(reader) -> [ while reader.Read() do let s = new CityType() s.Id <- reader.GetInt32 0 s.Name <- reader.GetString 1 s.StateName <- reader.GetString 3 ]), list.Empty ) This is my model type: type CityType() = inherit BaseType() let mutable name = "" let mutable stateName = "" member this.Name with get() = name and set restnameval=name <- restnameval member this.StateName with get() = stateName and set stateidval=stateName <- stateidval override this.ToSqlValuesList = [this.Name;] override this.ToFKValuesList = [StateType(Name=this.StateName);] The purpose for this FindIdByType function is that I want to find the id for a foreign key relationship, so I can set the value in my model and then have the CRUD functions do the operations with all the correct information. So, City needs the id for the state name, so I would get the state name, put it into the state type, then call this function to get the id for that state, so my city insert will also include the id for the foreign key. This seems to be the best approach, in a very generic way to handle inserts, which is the current problem I am trying to solve.

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  • Java - Circular Garbage Collection

    - by aloh
    A <- B <- C <- D <- A... // A is firstNode, D is lastNode if ( length == 1 ) { firstNode = null; lastNode = null; firstNode.next = null; firstNode.prev = null; } else { Node secondNode = firstNode.next; Node secondToLast = lastNode.prev; firstNode.next = null; firstNode.prev = null; lastNode.next = null; lastNode.prev = null; secondNode.prev = null; secondToLast.next = null; firstNode = null; lastNode = null; } That should send everything in between as candidates for garbage collection, I hope?

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  • Problem with circular definition in Scheme

    - by user8472
    I am currently working through SICP using Guile as my primary language for the exercises. I have found a strange behavior while implementing the exercises in chapter 3.5. I have reproduced this behavior using Guile 1.4, Guile 1.8.6 and Guile 1.8.7 on a variety of platforms and am certain it is not specific to my setup. This code works fine (and computes e): (define y (integral (delay dy) 1 0.001)) (define dy (stream-map (lambda (x) x) y)) (stream-ref y 1000) The following code should give an identical result: (define (solve f y0 dt) (define y (integral (delay dy) y0 dt)) (define dy (stream-map f y)) y) (solve (lambda (x) x) 1 0.001) But it yields the error message: standard input:7:14: While evaluating arguments to stream-map in expression (stream-map f y): standard input:7:14: Unbound variable: y ABORT: (unbound-variable) So when embedded in a procedure definition, the (define y ...) does not work, whereas outside the procedure in the global environment at the REPL it works fine. What am I doing wrong here? I can post the auxiliary code (i.e., the definitions of integral, stream-map etc.) if necessary, too. With the exception of the system-dependent code for cons-stream, they are all in the book. My own implementation of cons-stream for Guile is as follows: (define-macro (cons-stream a b) `(cons ,a (delay ,b)))

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  • Circular gradient in android

    - by sandis
    Im trying to make a gradient that emits from the middle of the screen in white, and turns to black as it moves toward the edges of the screen. As I make a "normal" gradient like this, I have been experimenting with different shapes: <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle"> <gradient android:startColor="#E9E9E9" android:endColor="#D4D4D4" android:angle="270"/> </shape> When using the "oval"-shape I at least got a round shape, but there were no gradient effect. How can I achieve this? Cheers,

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  • implementation of a queue using a circular array

    - by matin1234
    Hi I have found these algorithms in the internet but I can not understand that why in the enqueue method we compare size with N-1??? please help me thanks!! Algorithm size(): return (N-f+r)mod N Algorithm enqueue(e): if size()=N-1 then throw a FullQueueException Q[r]<---e r<----(r+1)mod N

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  • C++ circular dependency - namespace vs struct

    - by Dead or Alive
    Please educate me. Why does this compile: struct compiles { struct A; struct B { B(const A &a) : member(a.member) { } int member; }; struct A { A(const B &b) : member(b.member) { } int member; }; }; while this does not: namespace doesnt { struct A; struct B { B(const A &a) : member(a.member) { } int member; }; struct A { A(const B &b) : member(b.member) { } int member; }; } (in MSVC 9.0)

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  • Generics with constraints hierarchy

    - by devoured elysium
    I am currently facing a very disturbing problem: interface IStateSpace<Position, Value> where Position : IPosition // <-- Problem starts here where Value : IValue // <-- and here as I don't { // know how to get away this // circular dependency! // Notice how I should be // defining generics parameters // here but I can't! Value GetStateAt(Position position); void SetStateAt(Position position, State state); } As you'll down here, both IPosition, IValue and IState depend on each other. How am I supposed to get away with this? I can't think of any other design that will circumvent this circular dependency and still describes exactly what I want to do! interface IState<StateSpace, Value> where StateSpace : IStateSpace where Value : IValue { StateSpace StateSpace { get; }; Value Value { get; set; } } interface IPosition { } interface IValue<State> where State : IState { State State { get; } } Basically I have a state space IStateSpace that has states IState inside. Their position in the state space is given by an IPosition. Each state then has one (or more) values IValue. I am simplifying the hierarchy, as it's a bit more complex than described. The idea of having this hierarchy defined with generics is to allow for different implementations of the same concepts (an IStateSpace will be implemented both as a matrix as an graph, etc). Would can I get away with this? How do you generally solve this kind of problems? Which kind of designs are used in these cases? Thanks

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  • Resolving a Forward Declaration Issue Involving a State Machine in C++

    - by hypersonicninja
    I've recently returned to C++ development after a hiatus, and have a question regarding implementation of the State Design Pattern. I'm using the vanilla pattern, exactly as per the GoF book. My problem is that the state machine itself is based on some hardware used as part of an embedded system - so the design is fixed and can't be changed. This results in a circular dependency between two of the states (in particular), and I'm trying to resolve this. Here's the simplified code (note that I tried to resolve this by using headers as usual but still had problems - I've omitted them in this code snippet): #include <iostream> #include <memory> using namespace std; class Context { public: friend class State; Context() { } private: State* m_state; }; class State { public: State() { } virtual void Trigger1() = 0; virtual void Trigger2() = 0; }; class LLT : public State { public: LLT() { } void Trigger1() { new DH(); } void Trigger2() { new DL(); } }; class ALL : public State { public: ALL() { } void Trigger1() { new LLT(); } void Trigger2() { new DH(); } }; // DL needs to 'know' about DH. class DL : public State { public: DL() { } void Trigger1() { new ALL(); } void Trigger2() { new DH(); } }; class HLT : public State { public: HLT() { } void Trigger1() { new DH(); } void Trigger2() { new DL(); } }; class AHL : public State { public: AHL() { } void Trigger1() { new DH(); } void Trigger2() { new HLT(); } }; // DH needs to 'know' about DL. class DH : public State { public: DH () { } void Trigger1() { new AHL(); } void Trigger2() { new DL(); } }; int main() { auto_ptr<LLT> llt (new LLT); auto_ptr<ALL> all (new ALL); auto_ptr<DL> dl (new DL); auto_ptr<HLT> hlt (new HLT); auto_ptr<AHL> ahl (new AHL); auto_ptr<DH> dh (new DH); return 0; } The problem is basically that in the State Pattern, state transitions are made by invoking the the ChangeState method in the Context class, which invokes the constructor of the next state. Because of the circular dependency, I can't invoke the constructor because it's not possible to pre-define both of the constructors of the 'problem' states. I had a look at this article, and the template method which seemed to be the ideal solution - but it doesn't compile and my knowledge of templates is a rather limited... The other idea I had is to try and introduce a Helper class to the subclassed states, via multiple inheritance, to see if it's possible to specify the base class's constructor and have a reference to the state subclasse's constructor. But I think that was rather ambitious... Finally, would a direct implmentation of the Factory Method Design Pattern be the best way to resolve the entire problem?

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  • Java: how to avoid circual references when dumping object information with reflection?

    - by Tom
    I've modified an object dumping method to avoid circual references causing a StackOverflow error. This is what I ended up with: //returns all fields of the given object in a string public static String dumpFields(Object o, int callCount, ArrayList excludeList) { //add this object to the exclude list to avoid circual references in the future if (excludeList == null) excludeList = new ArrayList(); excludeList.add(o); callCount++; StringBuffer tabs = new StringBuffer(); for (int k = 0; k < callCount; k++) { tabs.append("\t"); } StringBuffer buffer = new StringBuffer(); Class oClass = o.getClass(); if (oClass.isArray()) { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("["); for (int i = 0; i < Array.getLength(o); i++) { if (i < 0) buffer.append(","); Object value = Array.get(o, i); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if (value.getClass().isPrimitive() || value.getClass() == java.lang.Long.class || value.getClass() == java.lang.String.class || value.getClass() == java.lang.Integer.class || value.getClass() == java.lang.Boolean.class) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } buffer.append(tabs.toString()); buffer.append("]\n"); } else { buffer.append("\n"); buffer.append(tabs.toString()); buffer.append("{\n"); while (oClass != null) { Field[] fields = oClass.getDeclaredFields(); for (int i = 0; i < fields.length; i++) { if (fields[i] == null) continue; buffer.append(tabs.toString()); fields[i].setAccessible(true); buffer.append(fields[i].getName()); buffer.append("="); try { Object value = fields[i].get(o); if (value != null) { if (excludeList.contains(value)) { buffer.append("circular reference"); } else if ((value.getClass().isPrimitive()) || (value.getClass() == java.lang.Long.class) || (value.getClass() == java.lang.String.class) || (value.getClass() == java.lang.Integer.class) || (value.getClass() == java.lang.Boolean.class)) { buffer.append(value); } else { buffer.append(dumpFields(value, callCount, excludeList)); } } } catch (IllegalAccessException e) { System.out.println("IllegalAccessException: " + e.getMessage()); } buffer.append("\n"); } oClass = oClass.getSuperclass(); } buffer.append(tabs.toString()); buffer.append("}\n"); } return buffer.toString(); } The method is initially called like this: System.out.println(dumpFields(obj, 0, null); So, basically I added an excludeList which contains all the previousely checked objects. Now, if an object contains another object and that object links back to the original object, it should not follow that object further down the chain. However, my logic seems to have a flaw as I still get stuck in an infinite loop. Does anyone know why this is happening?

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  • Game Objects Talking To Each Other

    - by PhilCK
    What is a good way of dealing with objects and having them talk to each other? Up until now all my games hobby/student have been small so this problem was generally solved in a rather ugly way, which lead to tight integration and circular dependencies. Which was fine for the size of projects I was doing. However my projects have been getting bigger in size and complexity and now I want to start re-using code, and making my head a simpler place. The main problem I have is generally along the lines of Player needs to know about the Map and so does the Enemy, this has usually descended into setting lots of pointers and having lots of dependencies, and this becomes a mess quickly. I have thought along the lines of a message style system. but I cant really see how this reduces the dependencies, as I would still be sending the pointers everywhere. Thanks. PS: I guess this has been discussed before, but I don't know what its called just the need I have.

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  • How can I get my business objects layer to use the management layer in their methods?

    - by Tom Pickles
    I have a solution in VS2010 with several projects, each making up a layer within my application. I have business entities which are currently objects with no methods, and I have a management layer which references the business entities layer in it's project. I now think I have designed my application poorly and would like to move methods from helper classes (which are in another layer) into methods I'll create within the business entities themselves. For example I have a VirtualMachine object, which uses a helper class to call a Reboot() method on it which passes the request to the management layer. The static manager class talks to an API that reboots the VM. I want to move the Reboot() method into the VirtualMachine object, but I will need to reference the management layer: public void Reboot() { VMManager.Reboot(this.Name); } So if I add a reference to my management project in my entities project, I get the circular dependency error, which is how it should be. How can I sort this situation out? Do I need to an yet another layer between the entity layer and the management layer? Or, should I just forget it and leave it as it is. The application works ok now, but I am concerned my design isn't particularly OOP centric and I would like to correct this.

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