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  • Singletons and constants

    - by devoured elysium
    I am making a program which makes use of a couple of constants. At first, each time I needed to use a constant, I'd define it as //C# private static readonly int MyConstant = xxx; //Java private static final int MyConstant = xxx; in the class where I'd need it. After some time, I started to realise that some constants would be needed in more than one class. At this time, I had 3 choises: To define them in the different classes that needed it. This leads to repetition. If by some reason later I need to change one of them, I'd have to check in all classes to replace them everywhere. To define a static class/singleton with all the constants as public. If I needed a constant X in ClassA, ClassB and ClassC, I could just define it in ClassA as public, and then have ClassB and ClassC refer to them. This solution doesn't seem that good to me as it introduces even more dependencies as the classes already have between them. I ended up implementing my code with the second option. Is that the best alternative? I feel I am probably missing some other better alternative. What worries me about using the singleton here is that it is nowhere clear to a user of the class that this class is using the singleton. Maybe I could create a ConstantsClass that held all the constants needed and then I'd pass it in the constructor to the classes that'd need it? Thanks

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  • Is it possible to start (and stop) a thread inside a DLL?

    - by Jerry Dodge
    I'm pondering some ideas for building a DLL for some common stuff I do. One thing I'd like to check if it's possible is running a thread inside of a DLL. I'm sure I would be able to at least start it, and have it automatically free on terminate (and make it forcefully terminate its self) - that I can see wouldn't be much of a problem. But once I start it, I don't see how I can continue communicating with it (especially to stop it) mainly because each call to the DLL is unique (as far as my knowledge tells me) but I also know very little of the subject. I've seen how in some occasions, a DLL can be loaded at the beginning and released at the end when it's not needed anymore. I have 0 knowledge or experience with this method, other than just seeing something related to it, couldn't even tell you what or how, I don't remember. But is this even possible? I know about ActiveX/COM but that is not what I want - I'd like just a basic DLL that can be used across languages (specifically C#). Also, if it is possible, then how would I go about doing callbacks from the DLL to the app? For example, when I start the thread, I most probably will assign a function (which is inside the EXE) to be the handler for the events (which are triggered from the DLL). So I guess what I'm asking is - how to load a DLL for continuous work and release it when I'm done - as opposed to the simple method of calling individual functions in the DLL as needed. In the same case - I might assign variables or create objects inside the DLL. How can I assure that once I assign that variable (or create the object), how can I make sure that variable or object will still be available the next time I call the DLL? Obviously it would require a mechanism to Initialize/Finalize the DLL (I.E. create the objects inside the DLL when the DLL is loaded, and free the objects when the DLL is unloaded). EDIT: In the end, I will wrap the DLL inside of a component, so when an instance of the component is created, DLL will be loaded and a corresponding thread will be created inside the DLL, then when the component is free'd, the DLL is unloaded. Also need to make sure that if there are for example 2 of these components, that there will be 2 instances of the DLL loaded for each component. Is this in any way related to the use of an IInterface? Because I also have 0 experience with this. No need to answer it directly with sample source code - a link to a good tutorial would be great.

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  • Python: What's a correct and good way to implement __hash__()?

    - by random-name
    What's a correct and good way to implement hash()? I am talking about the function that returns a hashcode that is then used to insert objects into hashtables aka dictionaries. As hash() returns an integer and is used for "binning" objects into hashtables I assume that the values of the returned integer should be uniformly distributed for common data (to minimize collisions). What's a good practice to get such values? Are collisions a problem? In my case I have a small class which acts as a container class holding some ints, some floats and a string.

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  • The cross-thread usage of "HttpContext.Current" property and related things

    - by smwikipedia
    I read from < Essential ASP.NET with Examples in C# the following statement: Another useful property to know about is the static Current property of the HttpContext class. This property always points to the current instance of the HttpContext class for the request being serviced. This can be convenient if you are writing helper classes that will be used from pages or other pipeline classes and may need to access the context for whatever reason. By using the static Current property to retrieve the context, you can avoid passing a reference to it to helper classes. For example, the class shown in Listing 4-1 uses the Current property of the context to access the QueryString and print something to the current response buffer. Note that for this static property to be correctly initialized, the caller must be executing on the original request thread, so if you have spawned additional threads to perform work during a request, you must take care to provide access to the context class yourself. I am wondering about the root cause of the bold part, and one thing leads to another, here is my thoughts: We know that a process can have multiple threads. Each of these threads have their own stacks, respectively. These threads also have access to a shared memory area, the heap. The stack then, as I understand it, is kind of where all the context for that thread is stored. For a thread to access something in the heap it must use a pointer, and the pointer is stored on its stack. So when we make some cross-thread calls, we must make sure that all the necessary context info is passed from the caller thread's stack to the callee thread's stack. But I am not quite sure if I made any mistake. Any comments will be deeply appreciated. Thanks. ADD Here the stack is limited to user stack.

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  • Does this pattern have a name?

    - by LK7jb
    Disclaimer: I'm trying to learn proper OO programming/design, so I'm pretty new to this stuff. I guess this is a general design patterns question, but I'll base my example on a game engine or something that renders objects to the display. Consider the following: How can this sort of separation between physical objects (e.g., cubes, spheres, etc.) and the rendering mechanism be achieved in an extensible manner? This design is not set in stone, and perhaps I've got something wrong from the start. I'm just curious as to how a problem like this is solved in real world code.

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  • C# determining generic type

    - by Chris Klepeis
    I have several templated objects that all implement the same interface: I.E. MyObject<datatype1> obj1; MyObject<datatype2> obj2; MyObject<datatype3> obj3; I want to store these objects in a List... I think I would do that like this: private List<MyObject<object>> _myList; I then want to create a function that takes 1 parameter, being a datatype, to see if an object using that datatype exists in my list.... sorta clueless how to go about this. In Pseudo code it would be: public bool Exist(DataType T) { return (does _myList contain a MyObject<T>?); }

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  • XML .NET Library

    - by osss
    Is it any XML .net library like simplexml in PHP? For example: <root> <obj> <val>value1</val> </obj> <obj> <val>value1</val> </obj> </root> objects = .....Parse(xml); Console.WriteLine(objects[0].val.ToString());

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  • Reverse Search Best Practices?

    - by edub
    I'm making an app that has a need for reverse searches. By this, I mean that users of the app will enter search parameters and save them; then, when any new objects get entered onto the system, if they match the existing search parameters that a user has saved, a notification will be sent, etc. I am having a hard time finding solutions for this type of problem. I am using Django and thinking of building the searches and pickling them using Q objects as outlined here: http://www.djangozen.com/blog/the-power-of-q The way I see it, when a new object is entered into the database, I will have to load every single saved query from the db and somehow run it against this one new object to see if it would match that search query... This doesn't seem ideal - has anyone tackled such a problem before?

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  • list of all commits SHA1_HASH

    - by dorelal
    git init echo 'I am foo' > foo.txt git add foo.txt # this woould create a git commit object echo ' I am foo2' > foo.txt git add foo.txt # this would create another git commit object git commit -m 'doe' # this would create two git # objects: one commit object and one tree object How do I get a list of all 4 commits SHA1_HASH ? cd .git/objects ls (master)$ ls -al total 0 drwxr-xr-x 8 nsingh staff 272 Mar 27 16:44 . drwxr-xr-x 13 nsingh staff 442 Mar 27 16:44 .. drwxr-xr-x 3 nsingh staff 102 Mar 27 16:44 37 drwxr-xr-x 3 nsingh staff 102 Mar 27 16:43 a2 drwxr-xr-x 3 nsingh staff 102 Mar 27 16:44 e1 drwxr-xr-x 3 nsingh staff 102 Mar 27 16:42 e6 drwxr-xr-x 2 nsingh staff 68 Mar 27 16:42 info drwxr-xr-x 2 nsingh staff 68 Mar 27 16:42 pack I can find the list of all 4 commits by looking at file here but there must be a better way.

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  • Django: Converting an entire Model into a single dictionary

    - by LarrikJ
    Is there a good way in Django to convert an entire model to a dictionary? I mean, like this: class DictModel(models.Model): key = models.CharField(20) value = models.CharField(200) DictModel.objects.all().to_dict() ... with the result being a dictionary with the key/value pairs made up of records in the Model? Has anyone else seen this as being useful for them? Thanks. Update I just wanted to add is that my ultimate goal is to be able to do a simple variable lookup inside a Template. Something like: {{ DictModel.exampleKey }} With a result of DictModel.objects.get(key__exact=exampleKey).value Overall, though, you guys have really surprised me with how helpful allof your responses are, and how different the ways to approach it can be. Thanks a lot.

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  • Constructor initialising an array of subobjects?

    - by ojw
    Say I have several objects within a class, each of which needs constructing with a different value. I can write something like this: class b { public: b(int num) { // 1 for a.b1, and 2 for a.b2 } }; class a { public: b b1; b b2; a() : b1(1), b2(2) { } }; However, is it possible to do the same thing if those multiple objects are stored in an array? My first attempt at it doesn't compile: class a { public: b bb[2]; a() : bb[0](1), bb[1](2) { } };

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  • Order a List (C#) by many fields?

    - by Esabe
    Hi everyone, I want to order a List of objects in C# by many fields, not just by one. For example, let's suppose I have a class called X with two Attributes, A and B, and I have the following objects, in that order: object1 = A = "a", B = "h" object2 = A = "a", B = "c" object3 = A = "b", B = "x" object4 = A = "b", B = "b" and I want to order the list by A attribute first, and when they are equals, by B element, so the order would be: "a" "c" "a" "h" "b" "b" "b" "x" As far as I know, the OrderBy method order by one parameter. Question: How can I order a C# List by more than one field? Thank you very much

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  • Java PropertyChangeListener

    - by Laphroaig
    Hi, i'm trying to figure out how to listen a property change on another class. this is my code: class with the property to listen: public class ClassWithProperty { private PropertyChangeSupport changes = new PropertyChangeSupport(this); private int usersOnline; public int getUsersOnline() { return usersOnline; } public ClassWithProperty() { usersOnline = 0; while (usersOnline<10) { changes.firePropertyChange("usersOnline", usersOnline, usersOnline++); } } public void addPropertyChangeListener( PropertyChangeListener l) { changes.addPropertyChangeListener(l); } public void removePropertyChangeListener( PropertyChangeListener l) { changes.removePropertyChangeListener(l); } } class where i need to know when the property change: public class Main { private static ClassWithProperty test; public static void main(String[] args) { test = new ClassWithProperty(); test.addPropertyChangeListener(listen()); } private static PropertyChangeListener listen() { System.out.println(test.getUsersOnline()); return null; } } I have the event fired only the last time (usersOnline=10). Sorry if it can be a stupid question, i'm learning now java and can't find a solution.

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  • Foreign Key Relationships

    - by Yehonathan Quartey
    I have two models class Subject(models.Model): name = models.CharField(max_length=100,choices=COURSE_CHOICES) created = models.DateTimeField('created', auto_now_add=True) modified = models.DateTimeField('modified', auto_now=True) syllabus = models.FileField(upload_to='syllabus') def __unicode__(self): return self.name and class Pastquestion(models.Model): subject=models.ForeignKey(Subject) year =models.PositiveIntegerField() questions = models.FileField(upload_to='pastquestions') def __unicode__(self): return str(self.year) Each Subject can have one or more past questions but a past question can have only one subject. I want to get a subject, and get its related past questions of a particular year. I was thinking of fetching a subject and getting its related past question. Currently am implementing my code such that I rather get the past question whose subject and year correspond to any specified subject like this_subject=Subject.objects.get(name=the_subject) thepastQ=Pastquestion.objects.get(year=2000,subject=this_subject) I was thinking there is a better way to do this. Or is this already a better way? Please Do tell ?

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  • Dispatching generic tasks in WCF or .Net Remoting

    - by Eric
    Hello all, I've been researching for a couple days on and off, and have yet to figure out the best way to achieve the following goal. I would like to define either an interface or abstract class in C# which has an associated Run method, similar to the Java runnable interface. The goal would be to have a shared queue which contains a list of these objects. Then individual clients would be able to derive their own concrete runnable classes and add them to the queue hosted by the server. Clients would also be able to pop these runnable objects off the queue and execute them arbitrarily. This seems like it should be feasible in a VM based language without needing to place any of the concrete implementations in a shared assembly, but I have thus far had no luck finding a working example of such a system. Does anyone know how this might be achieved?

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  • FLEX: how to ignore MouseEvents from the container ?

    - by Patrick
    hi, I've some objects on the canvas, and I added eventListeners to these objects for MOUSE_UP event. I'm know checking if it works by tracing e.target.name, and I found out that the event is triggered twice, before on the element container (Canvas) and then the element itself. I read several times the documentation about Capture, Bubbling etc.. but I don't understand how to trigger the events only from the element itself... child.addEventListener(MouseEvent.MOUSE_UP, updateSelectedTags); private function updateSelectedTags(e:MouseEvent):void { Alert.show(e.currentTarget.name); //I have 2 alerts, one for canvas, the other one for the child } } thanks

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  • Associate two sets of values

    - by PJW
    I have the following code - public static int GetViewLevel(string viewLevelDesc) { try { switch (viewLevelDesc) { case "All": return 0; case "Office": return 10; case "Manager": return 50; default: throw new Exception("Invalid View Level Description"); } } catch (Exception eX) { throw new Exception("Action: GetViewLevel()" + Environment.NewLine + eX.Message); } } public static string GetViewLevelDescription(int viewLevel) { try { switch (viewLevel) { case 0: return "All"; case 10: return "Office"; case 50: return "Manager"; default: throw new Exception("Invalid View Level Description"); } } catch (Exception eX) { throw new Exception("Action: GetViewLevelDescription()" + Environment.NewLine + eX.Message); } } The two static Methods enable me to either get an int ViewLevel from a string ViewLevelDesc or vice versa. I'm sure the way I have done this is far more cumbersome than it needs to be, and I'm looking for some advice how to achieve the same objective but more concisely. The list of int / string pairs will increase significantly. The ones in the above code are just the first three I intend to use.

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  • [C++] Simple inheritance question

    - by xbonez
    I was going over some sample questions for an upcoming test, and this question is totally confusing me. Any help would be appreciated. Consider the following code: class GraduateStudent : public Student { ... }; If the word "public" is omitted, GraduateStudent uses private inheritance, which means which of the following? GraduateStudent objects may not use methods of Student. GraduateStudent does not have access to private objects of Student. No method of GraduateStudent may call a method of Student. Only const methods of GraduateStudent can call methods of Student.

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  • Is there any alternative way of writing this switch statement(C#3.0)

    - by Newbie
    Can it be done in a better way public static EnumFactorType GetFactorEnum(string str) { Standardization e = new Standardization(); switch (str.ToLower()) { case "beta": e.FactorType = EnumFactorType.BETA; break; case "bkp": e.FactorType = EnumFactorType.BOOK_TO_PRICE; break; case "yld": e.FactorType = EnumFactorType.DIVIDEND_YIELD; break; case "growth": e.FactorType = EnumFactorType.GROWTH; break; case "mean": e.FactorType = EnumFactorType.MARKET_CAP; break; case "momentum": e.FactorType = EnumFactorType.MOMENTUM; break; case "size": e.FactorType = EnumFactorType.SIZE; break; case "stat_fact1": e.FactorType = EnumFactorType.STAT_FACT_1; break; case "stat_fact2": e.FactorType = EnumFactorType.STAT_FACT_2; break; case "value": e.FactorType = EnumFactorType.VALUE; break; } return e.FactorType; } If I create a Static class(say Constatant) and declare variable like public static string BETA= "beta"; and then if I try to put that in the Case expression like Case Constants.BETA : e.FactorType = EnumFactorType.BETA; break; then the compiler will report error.(quite expected) So is there any other way?(I canot change the switch statement) Using C#3.0 Thanks

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  • What type of data should I send to view?

    - by Vizualni
    Hello, this question I've been asking myself since the day I started programming in MVC way. Should I send to view arrays filled with data or should I send it as on objects I retrieved from database? My model returns me data as objects. What would be the best way to create such a thing? $new_data = $model->find_by_id(1); echo $new_data->name; $new_data->name= "whatever"; $new_data->save(); For example. view.php echo $object->name; or echo $array['name'] Language is php :).

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  • Data Structure Brushup (Java)

    - by Daddy Warbox
    This should be easy for many of you, but for me it's just another bit of rust needing to be chipped away as I get back into basic Java coding. Using bloody associative arrays for so long in other languages have turned me nice and spoiled. :P My problem is simple: I'm storing a set of objects, each containing a string and a number, in a list. I would like each object inserted into this list to be sorted alphabetically by its string. I would also like to be able to retrieve objects from the list by their string as well. I would like to do this as formally and/or efficiently as possible. Is there something already available in the Java standard libraries for this?

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  • Is it possible to Store Enum value in String?

    - by Narasimham K
    Actally my java progrem like... public class Schedule{ public static enum RepeatType { DAILY, WEEKLY, MONTHLY; } public static enum WeekdayType { MONDAY(Calendar.MONDAY), TUESDAY(Calendar.TUESDAY), WEDNESDAY( Calendar.WEDNESDAY), THURSDAY(Calendar.THURSDAY), FRIDAY( Calendar.FRIDAY), SATURDAY(Calendar.SATURDAY), SUNDAY( Calendar.SUNDAY); private int day; private WeekdayType(int day) { this.day = day; } public static List<Date> generateSchedule(RepeatType repeatType,List<WeekdayType> repeatDays) { ----------------------------- ----------------------------//hear some logic i wrote }//Method } And i'm calling the method into my Business class like following... @RemotingInclude public void createEvent(TimetableVO timetableVO) { if ("repeatDays".equals(timetableVO.getSearchKey())) { List<Date> repeatDaysList=Schedule.generateSchedule(timetableVO.getRepeatType(),timetableVO.getRepeatDays()); } } And Finally TimetableVO is @Entity @Table(name="EC_TIMETABLE") public class TimetableVO extends AbstractVO{ ----- private RepeatType repeatType; private List<WeekdayType> repeatDays;//But in this case the method generateSchedule(-,-) was not calling. ----- } So my Question is Which one is Better Statement in the Following... private List<WeekdayType> repeatDays; (or) private String repeatDays;//if we give like this `How to Convert Enum type to String` because generateSchedule() method taking enum type value....

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  • Finding an odd perfect number

    - by Coin Bird
    I wrote these two methods to determine if a number is perfect. My prof wants me to combine them to find out if there is an odd perfect number. I know there isn't one(that is known), but I need to actually write the code to prove that. The issue is with my main method. I tested the two test methods. I tried debugging and it gets stuck on the number 5, though I can't figure out why. Here is my code: public class Lab6 { public static void main (String[]args) { int testNum = 3; while (testNum != sum_of_divisors(testNum) && testNum%2 != 0) testNum++; } public static int sum_of_divisors(int numDiv) { int count = 1; int totalDivisors = 0; while (count < numDiv) if (numDiv%count == 0) { totalDivisors = totalDivisors + count; count++; } else count++; return totalDivisors; } public static boolean is_perfect(int numPerfect) { int count = 1; int totalPerfect = 0; while (totalPerfect < numPerfect) { totalPerfect = totalPerfect + count; count++; } if (numPerfect == totalPerfect) return true; else return false; } }

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