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  • Circular dependency with generics

    - by devoured elysium
    I have defined the following interface: public interface IStateSpace<State, Action> where State : IState where Action : IAction<State, Action> // <-- this is the line that bothers me { void SetValueAt(State state, Action action); Action GetValueAt(State state); } Basically, an IStateSpace interface should be something like a chess board, and in each position of the chess board you have a set of possible movements to do. Those movements here are called IActions. I have defined this interface this way so I can accommodate for different implementations: I can then define concrete classes that implement 2D matrix, 3D matrix, graphs, etc. public interface IAction<State, Action> { IStateSpace<State, Action> StateSpace { get; } } An IAction, would be to move up(this is, if in (2, 2) move to (2, 1)), move down, etc. Now, I'll want that each action has access to a StateSpace so it can do some checking logic. Is this implementation correct? Or is this a bad case of a circular dependence? If yes, how to accomplish "the same" in a different way? Thanks

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  • Base class with abstract subclasses in C# ?

    - by Nick Brooks
    public abstract class Request { public class Parameters { //Threre are no members here //But there should be in inherited classes } public Request() { parameters = new Parameters(); } public Parameters parameters; } Two questions: How do I make it so I can add stuff to the constructor but the original constructor will still be executed? How do I make it so the subclasses can add members to the Parameters class?

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  • How to extend this design for a generic converter in java?

    - by Jay
    Here is a small currency converter piece of code: public enum CurrencyType { DOLLAR(1), POUND(1.2), RUPEE(.25); private CurrencyType(double factor) { this.factor = factor; } private double factor; public double getFactor() { return factor; } } public class Currency { public Currency(double value, CurrencyType type) { this.value = value; this.type = type; } private CurrencyType type; private double value; public CurrencyType getCurrencyType() { return type; } public double getCurrencyValue() { return value; } public void setCurrenctyValue(double value){ this.value = value; } } public class CurrencyConversion { public static Currency convert(Currency c1, Currency c2) throws Exception { if (c1 != null && c2 != null) { c2.setCurrenctyValue(c1.getCurrencyValue() * c1.getCurrencyType().getFactor() * c2.getCurrencyType().getFactor()); return c2; } else throw new Exception(); } } I would like to improve this code to make it work for different units of conversion, for example: kgs to pounds, miles to kms, etc etc. Something that looks like this: public class ConversionManager<T extends Convertible> { public T convert(T c1, T c2) { //return null; } } Appreciate your ideas and suggestions.

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  • Where to start .NET Entity Framework and ORM?

    - by Freshblood
    Hello I haven't used any database system enough but i believe i know logic of databases and i have learnt little sql so i shouldn't start to learn ORM before learn them well? Where can i start to learn .NET Entity Framework and which version of framework i have to start 3.5 or 4.0 because i heard that 4.0 has strong support for Entity Framework.I am looking sources web pages,e-books or other else.

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  • Designing different Factory classes (and what to use as argument to the factories!)

    - by devoured elysium
    Let's say we have the following piece of code: public class Event { } public class SportEvent1 : Event { } public class SportEvent2 : Event { } public class MedicalEvent1 : Event { } public class MedicalEvent2 : Event { } public interface IEventFactory { bool AcceptsInputString(string inputString); Event CreateEvent(string inputString); } public class EventFactory { private List<IEventFactory> factories = new List<IEventFactory>(); public void AddFactory(IEventFactory factory) { factories.Add(factory); } //I don't see a point in defining a RemoveFactory() so I won't. public Event CreateEvent(string inputString) { try { //iterate through all factories. If one and only one of them accepts //the string, generate the event. Otherwise, throw an exception. return factories.Single(factory => factory.AcceptsInputString(inputString)).CreateEvent(inputString); } catch (InvalidOperationException e) { throw new InvalidOperationException("No valid factory found to generate this kind of Event!", e); } } } public class SportEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("SportEvent1"); } public Event CreateEvent(string inputString) { return new SportEvent1(); } } public class MedicalEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("MedicalEvent1"); } public Event CreateEvent(string inputString) { return new MedicalEvent1(); } } And here is the code that runs it: static void Main(string[] args) { EventFactory medicalEventFactory = new EventFactory(); medicalEventFactory.AddFactory(new MedicalEvent1Factory()); medicalEventFactory.AddFactory(new MedicalEvent2Factory()); EventFactory sportsEventFactory = new EventFactory(); sportsEventFactory.AddFactory(new SportEvent1Factory()); sportsEventFactory.AddFactory(new SportEvent2Factory()); } I have a couple of questions: Instead of having to add factories here in the main method of my application, should I try to redesign my EventFactory class so it is an abstract factory? It'd be better if I had a way of not having to manually add EventFactories every time I want to use them. So I could just instantiate MedicalFactory and SportsFactory. Should I make a Factory of factories? Maybe that'd be over-engineering? As you have probably noticed, I am using a inputString string as argument to feed the factories. I have an application that lets the user create his own events but also to load/save them from text files. Later, I might want to add other kinds of files, XML, sql connections, whatever. The only way I can think of that would allow me to make this work is having an internal format (I choose a string, as it's easy to understand). How would you make this? I assume this is a recurrent situation, probably most of you know of any other more intelligent approach to this. I am then only looping in the EventFactory for all the factories in its list to check if any of them accepts the input string. If one does, then it asks it to generate the Event. If you find there is something wrong or awkward with the method I'm using to make this happen, I'd be happy to hear about different implementations. Thanks! PS: Although I don't show it in here, all the different kind of events have different properties, so I have to generate them with different arguments (SportEvent1 might have SportName and Duration properties, that have to be put in the inputString as argument).

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  • same flash file (.swf) downloaded multiple times on a page

    - by Gunjan
    I have a page that has a table with each row corresponding to an audio file. The last cell in each row embeds a simple flash audio player. The problem is that the flash file for the player is being downloaded for each row separately and as soon as rows go beyond 40-50 it crashes the browser. I tried using different players (1pixelout, flash-mp3-player) and the problem is still there, so its not a player specific issue. Is there any way to cache the player so that it is only downloaded once?

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  • Cohesion and Decoupling.

    - by dbtek
    Can anyone tell me what are Cohesion and Decoupling? I found coupling but there is no Decoupling anywhere. I need to learn their meanings. Any help will be appreciated. Thanks for replying.

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  • Why Java interfaces can't have constructors?

    - by AndrejaKo
    This question showed up on my mid-term exams and I've been searching for correct answer for some time. I know that Java interfaces can't be directly instantiated so they don't need constructors and that they can have only public static final attributes so they don't need constructors to set them up but that's not the expected answer.

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  • C# animation - move object from A to B or by angle

    - by Nullstr1ng
    Hi am just doing a little animation which moves an object from point a to point b or by angle/radians. what I currently have is this Point CalcMove(Point pt, double angle, int speed) { Point ret = pt; ret.X = (int)(ret.X + speed * Math.Sin(DegToRad(angle))); ret.Y = (int)(ret.Y + speed * Math.Cos(DegToRad(angle))); return ret; } but it doesn't look what i expected. please help? update: oh and am using NETCF

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  • Events in Classes (VB.NET)

    - by Otaku
    I find that I write a lot of code within my classes to keep properties in sync with each other. I've read about Events in Classes, but have not been able to wrap my head around how to make them work for what I'm looking for. I could use some advice here. For example, in this one I always want to keep myColor up to date with any change whatsoever in any or all of the Red, Green or Blue properties. Class myColors Private Property Red As Byte Private Property Green As Byte Private Property Blue As Byte Private Property myColor As Color Sub New() myColor = Color.FromArgb(0, 0, 0) End Sub Sub ChangeRed(ByVal r As Byte) Red = r myColor = Color.FromArgb(Red, Green, Blue) End Sub Sub ChangeBlue(ByVal b As Byte) Blue = b myColor = Color.FromArgb(Red, Green, Blue) End Sub End Class If one or more of those changes, I want myColor to be updated. Easy enough as above, but is there a way to work with events that would automatically do this so I don't have to put myColor = Color.FromArgb(Red, Green, Blue) in every sub routine?

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  • How to return a value when destroying/cleaning-up an object instance

    - by Mridang Agarwalla
    When I initiate a class in Python, I give it some values. I then call method in the class which does something. Here's a snippet: class TestClass(): def __init__(self): self.counter = 0 def doSomething(self): self.counter = self.counter + 1 print 'Hiya' if __name__ == "__main__": obj = TestClass() obj.doSomething() obj.doSomething() obj.doSomething() print obj.counter As you can see, everytime I call the doSomething method, it prints some text and increments an internal variable i.e. counter. When I initiate the class, i set the counter variable to 0. When I destroy the object, I'd like to return the internal counter variable. What would be a good way of doing this? I wanted to know if there were other ways apart from doing stuff like: accessing the variable directly. Like obj.counter. creating a method like getCounter. Thanks.

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  • Why does C# not provide the C++ style 'friend' keyword?

    - by Ash
    The C++ friend keyword allows a class A to designate class B as it's friend. This allows Class B to access the private/protected members of class A. I've never read anything as to why this was left out of C# (and VB.NET). Most answers to this earlier StackOverflow question seem to be saying it is a useful part of C++ and there are good reasons to use it. In my experience I'd have to agree. Another question seems to me to be really asking how to do something similar to friend in a C# application. While the answers generally revolve around nested classes, it doesn't seem quite as elegant as using the friend keyword. The original Design Patterns book uses the friend keyword regularly throughout its examples. So in summary, why is friend missing from C#, and what is the "best practice" way (or ways) of simulating it in C#? (By the way, the "internal" keyword is not the same thing, it allows ALL classes within the entire assembly to access internal members, friend allows you to give access to a class to just one other class.)

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  • jQuery object are immutable?

    - by Daniel
    Hello a new noob on jQuery here and I was wondering if jQuery objects are immutable. For example: var obj1 = $("<tag></tag>"); var obj2 = obj1.append("something"); Will obj1 and obj2 be the same meaning obj2 will reference obj1? UPDATE: The above example kind of scratches the surface of what i want to know, a more accurate question is : If i chain function from the jQuery api will they return the same object or a new one (as the case with strings in Java)?

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  • convert String "11-10-10 12:00:00" into Date Object

    - by Mahendra Athneria
    Hi, I want to convert String "11-10-10 12:00:00" into Date object but i am not able to do so. can you please help me out? below is the code snippet. i have the Date obj which has the value = Mon Oct 11 00:00:00 IST 2010 DateFormat newDateFormat = new SimpleDateFormat("dd-MM-yy hh:mm:ss"); String strDate = newDateFormat.format(tempDate); //**i got strDate as strDate is : 11-10-10 12:00:00** DateFormat newDateFormat1 = new SimpleDateFormat("dd-MM-yy hh:mm:ss"); try { tempDate = newDateFormat1.parse(strDate); // **getting tempDate as - Mon Oct 11 00:00:00 IST 2010** } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } Can someone help me to solve this issue? Regards, Mahendra Athneria Mumbai, India

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  • Strange Error - "Object moved to here."

    - by Dkong
    I get the strange error "Object moved to here." on a blank white page when I try to login on a site I created. It works fine locally but not when I deploy it to the test or production server. I am not doing anything odd, just using basic authentication code in a helper function as follows... public static bool AuthenticateUser(string Username, string Password, bool PersistLogin, string RedirectionURL) { if (Membership.ValidateUser(Username, Password)) { FormsAuthentication.SetAuthCookie(Username, PersistLogin); HttpContext.Current.Response.Redirect(RedirectionURL,true); return true; } else return false; }

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  • Doctrine: Relating a model to itself using a link table, like "This event is related to to the following other events"

    - by mattalexx
    So in English, the relationship would sound like "This event is related to to the following other events". My first instinct is to create an EventEvent model, with a first_event_id field and a second_event_id field. Then I would define the following two relationships in the Event model: $this->hasMany('Event as FirstRelatedEvents', array('local' => 'first_event_id', 'foreign' => 'second_event_id', 'refClass' => 'EventEvent')); $this->hasMany('Event as SecondRelatedEvents', array('local' => 'second_event_id', 'foreign' => 'first_event_id', 'refClass' => 'EventEvent')); But I would rather not have to use two relationships on the Event model. Is there a better way to do this?

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  • Do ORMs normally allow circular relations? If so, how would they handle it?

    - by SeanJA
    I was hacking around trying to make a basic orm that has support for the one => one and one => many relationships. I think I succeeded somewhat, but I am curious about how to handle circular relationships. Say you had something like this: user::hasOne('car'); car::hasMany('wheels'); car::property('type'); wheel::hasOne('car'); You could then do this (theoretically): $u = new user(); echo $u->car->wheels[0]->car->wheels[1]->car->wheels[2]->car->wheels[3]->type; #=> "monster truck" Now, I am not sure why you would want to do this. It seems like it wastes a whole pile of memory and time just to get to something that could have been done in a much shorter way. In my small ORM, I now have 4 copies of the wheel class, and 4 copies of the car class in memory, which causes a problem if I update one of them and save it back to the database, the rest get out of date, and could overwrite the changes that were already made. How do other ORMs handle circular references? Do they even allow it? Do they go back up the tree and create a pointer to one of the parents? DO they let the coder shoot themselves in the foot if they are silly enough to go around in circles?

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  • read java.security.key stored as object inside a file which is in jar

    - by Tal
    I saved a PublicKey instance in a file using ObjectOutputStream. This file is then stored inside a jar file which is then loaded by JBoss. I'm trying to read this file but it throws me an exception telling that it's not serializable. Here is the code : InputStream input = KeyLoader.class.getClassLoader().getResourceAsStream(resource); ObjectInputStream objectInputStream = new ObjectInputStream(input); Object obj = objectInputStream.readObject(); Key output = (Key) obj; objectInputStream.close(); return output; which throws me this exception An exception occurred: java.io.NotSerializableException

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  • Help with prototype object

    - by nemiss
    Hi, I am mlearning javascript and have some trouble creating an onject via prototype. I have this: <script type="text/javascript"> function myclass(a, b, c) { if (arguments.length) { this.Init(a, b, c); } } myclass.prototype.Init = function(a, b, c) { this.param1 = a; this.param2 = b; this.param3 = c; }; myclass.prototype.Print = function() { alert(this.param1 + '-' + this.param2 + '-' + this.param3); }; var myObject = myclass(3, 5, 6); myObject.Print(); </script> but I get an error on line with this.Init(a, b, c); Error: Object doesn't support this property or method

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  • Proxy object references in MVC code

    - by krystan honour
    Hi there, I am just figuring out best practice with MVC now I have a project where we have chosen to use it in anger. My question is. If creating a list view which is bound to an IEnumerable is this bad practise? Would it be better to seperate the code generated by the WCF Service reference into a datastructure which essentially holds the same data but abstracts further from the service, meaning that the UI is totally unaware of the service implementation beneath. or do people just bind to the proxy object types and have done with it ? My personal feeling is to create an abstraction but this seems to violate the DRY principle.

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  • jquery split() and indexOf results in "Object doesn't support this property or method"

    - by chris
    I have the following code: var selected = $('#hiddenField').val().split(","); ... if (selected.indexOf(id) > 0) { ... set value ... } I'm dynamically creating a CheckBoxList, and trying to remember the state of the checkboxes by putting the selected IDs into the hidden field. I get an error stating that "Object doesn't support this property or method". My assumption is that selected is an array, which should support indexOf. Is that incorrect?

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  • Question of using static_cast on "this" pointer in a derived object to base class

    - by Johnyy
    Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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  • How can I define an empty array in a Perl construtor?

    - by Laimoncijus
    I am just beginner with Perl, so if it sounds stupid - sorry for that :) My problem is - I am trying to write a class, which has an empty array, defined in constructor of a class. So I am doing this like this: package MyClass; use strict; sub new { my ($C) = @_; my $self = { items => () }; bless $self, ref $C || $C; } sub get { return $_[0]->{items}; } 1; Later I am testing my class with simple script: use strict; use Data::Dumper; use MyClass; my $o = MyClass->new(); my @items = $o->get(); print "length = ", scalar(@items), "\n", Dumper(@items); And while running the script I get following: $ perl my_test.pl length = 1 $VAR1 = undef; Why am I doing wrong what causes that I get my items array filled with undef? Maybe someone could show me example how the class would need to be defined so I would not get any default values in my array?

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