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• Reference variable to an object instantiated/initialized in another class in Java

  - by Alex

  The reason I'm asking is because I'm getting NullPointerException. I now this is very easy but I'm pretty new programming and find this a bit confusing. So say I have initialized an object in a class and want to access that same object from another class. Like now for instance I'm working on a small Chess game, in my model Game class I have an instance of Board, an object. Board, in turn, has an array of Squares. Square[][]. Game has board, board has Square[][]. Now if I want to access the Square[][] through the object board (in Game) of type Board. Do I just declare a variable with the same name and type or do I have to initialize it again? Board board OR Board board = new Board(); Note, I have already initialized board in the class Game so if I do it again, won't they be two totally different Board objects?

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• Sorting 1000-2000 elements with many cache misses

  - by Soylent Graham

  I have an array of 1000-2000 elements which are pointers to objects. I want to keep my array sorted and obviously I want to do this as quick as possible. They are sorted by a member and not allocated contiguously so assume a cache miss whenever I access the sort-by member. Currently I'm sorting on-demand rather than on-add, but because of the cache misses and [presumably] non-inlining of the member access the inner loop of my quick sort is slow. I'm doing tests and trying things now, (and see what the actual bottleneck is) but can anyone recommend a good alternative to speeding this up? Should I do an insert-sort instead of quicksorting on-demand, or should I try and change my model to make the elements contigious and reduce cache misses? OR, is there a sort algorithm I've not come accross which is good for data that is going to cache miss?

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• Examples of both beautiful and ugly java code?

  - by tputkonen

  I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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• How can I traverse a reverse generic relation in a Django template?

  - by user569139

  I have the following class that I am using to bookmark items: class BookmarkedItem(models.Model): is_bookmarked = models.BooleanField(default=False) user = models.ForeignKey(User) content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey() And I am defining a reverse generic relationship as follows: class Link(models.Model): url = models.URLField() bookmarks = generic.GenericRelation(BookmarkedItem) In one of my views I generate a queryset of all links and add this to a context: links = Link.objects.all() context = { 'links': links } return render_to_response('links.html', context) The problem I am having is how to traverse the generic relationship in my template. For each link I want to be able to check the is_bookmarked attribute and change the add/remove bookmark button according to whether the user already has it bookmarked or not. Is this possible to do in the template? Or do I have to do some additional filtering in the view and pass another queryset?

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• How to draw or put a text on empty an UITableViewController ?

  - by elementsense

  Hi I have a app that starts with a empty UITableViewController, which is pretty .. well, emtpy. Now I was wondering if I could hint the user by painting something else on the view, like pointing an arrow to the plus button and say something like "press here to add something new" I'll guess I have to do this in the viewDidLoad method, where I also init my NSFetchedResultsController, so I actually know if there are any objects in my list. I never put controls on the screen by code so I am not sure where to start and where to put em on. will that be the [self view] ? Thanks

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• Check if NSMutableArray contains text from textfield

  - by Polo Swelsen

  I want to check if the text inserted in a textfield is also in my NSMutableArray. So let's say my NSMutableArray has these objects: "Hey, Hello, No, Yes". Then when a user enters the text: "Hello" i want there to appear a UIAlertView. I now have the following: for (int slt = 0; slt < [zouten count]; slt++) { if (zout.text = [zouten objectAtIndex:slt]) { alert = [[UIAlertView alloc]initWithTitle:@"Goedzo!" message:[NSString stringWithFormat:@"Je hebt een zout gevonden"] delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; } } [alert show]; But somehow the message appears with every word. what am i doing wrong?

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• Multiple key map in c++

  - by Morgan

  Hi, I'm wondering if any of you know of a c++ associative map container type which I can perform multiple key lookups on. The map needs to have constant time lookups but I don't care if it's ordered or unordered. It just needs to be fast. For example, I want to store a bunch of std::vector objects in a map with an integer and a void* as the lookup keys. Both the int and the void* must match for my vector to be retrieved. Does anything like this exist already? Or am I going to have to roll my own. If so, any suggestions? I've been trying to store a boost::unordered_map inside another boost::unordered_map, but I have not had any success with this method yet. Maybe I will continue Pershing this method if there is no simpler way. Thanks!

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• NSCoding and ostream

  - by Stephen Furlani

  Is there a better way to serialize an ObjC object than using /NSKeyedArchive? I need to distribute the object through a C++ std:ostream-like object to put on another computer. The object has over 122 members of various types... for which wants me to [coder encodeObject: (id) forKey: @"blah"]; for all of them... Does anyone have a nice Perl Script that will at least write it out? I don't even know if the objects it contains implement which means this could turn into a huge ugly mess since I can't change the source of the object - I'll have to inherit & add the @interface to it... Or am I being dumb? Apple's guide doesn't help me since archiving to XML won't pass nicely though the ostream. Is there a better way to do this? -S!

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• How to resize a group of vectors in Expression Blend/WPF/Silverlight ?

  - by Shnitzel

  So say for example I created a few small squares in expression blend. I then group them together by selecting them, right clicking and selecting "Group Into - Grid" So now that they are in the grid, I'd like to be able to resize this grid and then they would resize but it doesn't happen, it just resizes the grid but leaves the vectors the same. Is there a way to do what I am looking for? p.s I know you can just select all the vectors and then resize them all, but I am looking for a way to just resize one container and not all the objects in there..

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• C++ Variable declarable in function body, but not class member?

  - by anon

  I want to create a C++ class with the following type: It can be declared inside of a function. It can be declared inside of a member function. It can not be declared as a class member. The use of this: think "Root" objects for a GC. Is this possible in C++? In particular, I'm using g++. Willing to switch to clang. Either templates or macro solution fine. Thanks!

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• Pass structured data from C++ app to ASP.NET web service.

  - by Odrade

  I have Visual C++ application that needs to communicate with a ASP.NET web service. Specifically, the app needs to pass structured data (e.g. objects that contain lists of structures, etc) as a parameter to one of the service methods. The C++ application is already generating an xml document that contains this data. The document is generating using an xml library, so it should always well-formed. What is a good method for passing this data to the web service? I'm thinking about passing the document to the web service as a string parameter, then deserializing to a .NET object based on an xsd. But, I hear that passing an xml doc as a string parameter is not recommended. So, my questions: What are the pitfalls associated with sending the document as a string parameter, assuming that the document itself is always well-formed? Assuming the above is a bad idea, what are some good alternate approaches?

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• PHP Casting as Object type in foreach Loop

  - by Coulton

  Within the following code, $quiz_object->personalities contains an array of Personality() objects. // Loop through each personality that exists for the quiz foreach($quiz_object->personalities AS $existing_personality) { // Show all of the existing personalities echo $existing_personality->GetQuizMakerPersonalityHTML(); } How do I "cast" (I think that's the right word) my variable $existing_personality within the foreach loop as the object type? I wish to do this so that when I type $existing_personality->, I get the list of public functions available for that object type. At the moment, Zend doesn't know that it refers to a Personality object within the loop.

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• Getting a random element in Django

  - by Sarah

  I just finished the Django tutorial and started work on my own project, however, I seem to have missed something completely. I wanted to get a random slogan from this model: from django.db import models class Slogan(models.Model): slogan = models.CharField(max_length=200) And return it in this view: from django.http import HttpResponse from swarm.sloganrotator.models import Slogan def index(request): return HttpResponse(Slogan.objects.order_by('?')[:1]) However, the view just returns 'Slogan object'. Then I thought, maybe I can access the slogan string itself by simply appending .slogan to the slice, but that gives me an error indicating that the object I have is actually a QuerySet and has no attribute slogan. I've obviously misunderstood something about Django here, but it just doesn't fall into place for me. Any help?

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• Proper usage of Java Weak Reference in case of nested collections

  - by Tong Wang

  I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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• iPhone - Create not persistant entities in core data

  - by ncohen

  Hi everyone, I would like to use entity objects but not store them... I read that I could create them like this: myElement = (Element *)[NSEntityDescription insertNewObjectForEntityForName:@"Element" inManagedObjectContext:managedObjectContext]; And right after that remove them: [managedObjectContext deleteObject:myElement]; then I can use my elements: myElement.property1 = @"Hello"; This works pretty well even though I think this is probably not the most optimal way to do it... Then I try to use it in my UITableView... the problem is that the object get released after the initialization. My table becomes empty when I move it! Thanks

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• Binding a select box to a Collection (with Spring)

  - by WiPU

  i have the following problem. I have a form bean and in this bean is a list with objects. List<SomeObjectForm> toDisplay; Now i want map a html select to this list. Something like that: <form:select id="inputGroupFields" path="templateKey" multiple="true"... <form:select id="inputGroupFields" path="templateKey.id" multiple="true"... And this dosnt work of course. Now i have tryed to add different custom Converter like: myConv implements Converter<SomeObjectForm, String> myConv extends StringToObject And this also not work. I'm not sure if this is the right approach or there is a easier way to do that. Some addional Infos: --i'm using spring 3.0.5 --all this happens during a web flow regards and thanks, WiPu

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• 3d movement around a sphere

  - by user578954

  Hey guys, Im working in 3d for the first time in a long time. Basically im rotating a sphere and projecting x y z cords to place things on the surface based on the spheres X and Y rotation. Heres the code im using: #define piover180 0.01745329252f GLfloat cosy = cos(yrot * piover180); island[i].x = rad * sin(xrot * piover180)* cosy; island[i].y = rad * sin(yrot * piover180); island[i].z = rad * cos(xrot * piover180) * cosy; Problem is the Xrot positioning works fine but the Yrot placement always draw the objects into the north and south pole so they all cross at the top, which isnt correct for rotating. I need a way to solve this. Heres a picture to help explain http://llllost.com/shuttle/47bcde62.jpg Any help would be greatly appreciated, let me know if you need any more information

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• Scala importing a file in all files of a package

  - by Core_Dumped

  I need to use an implicit ordering that has been defined in an object in a file abc in the following way: object abc{ implicit def localTimeOrdering: Ordering[LocalDate] = Ordering.fromLessThan(_.isBefore(_)) } So, I make a package object xyz inside a file 'package.scala' that in turn is in the package 'xyz' that has files in which I need the implicit ordering to be applicable. I write something like this: package object xyz{ import abc._ } It does not seem to work. If I manually write the implicit definition statement inside the package object, it works perfectly. What is the correct way to import the object (abc) such that all of its objects/classes/definitions can be used in my entire package 'xyz' ?

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• Java - Handling Non-Blocking Calls

  - by sarav

  In my application I am using a third-party API. It is a non-blocking method which returns immediately. I have a collection of elements over which I have to invoke this method. Now, my problem is that I have to find a way till all the method execution gets completed and do my next operation. How can I handle this? I cannot modify the third-party API. In short it looks like this for(Object object: objects){ methodA(object); //this is a non-blocking call and returns immediately } // here I want to do my next task only after all the methodA calls completed execution

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• Serialize an object to string

  - by Vaccano

  I have the following method to save an Object to a file: // Save an object out to the disk public static void SerializeObject<T>(this T toSerialize, String filename) { XmlSerializer xmlSerializer = new XmlSerializer(toSerialize.GetType()); TextWriter textWriter = new StreamWriter(filename); xmlSerializer.Serialize(textWriter, toSerialize); textWriter.Close(); } I confess I did not write it (I only converted it to a extension method that took a type parameter). Now I need it to give the xml back to me as a string (rather than save it to a file). I am looking into it, but I have not figured it out yet. I thought this might be really easy for someone familiar with these objects. If not I will figure it out eventually.

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• Nhibernate and not-exists query

  - by Dan

  I'm trying to construct a query in NHibernate to return a list of customers with no orders matching a specific criteria. My Customer object contains a set of Orders: <set name="Orders"> <key column="CustomerID" /> <one-to-many class="Order" /> </set> How do I contruct a query using NHibernate's ICriteria API to get a list of all customers who have no orders? Using native SQL, I am able to represent the query like this: select * from tblCustomers c where not exists (select 1 from tblOrders o where c.ID = o.CustomerID) I have been unable to figure out how to do this using aliases and DetatchedCriteria objects. Any guidance would be appreciated! Thanks!

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• transform file/directory structure into 'tree' in javascript

  - by dave

  I have an array of objects that looks like this: [{ name: 'test', size: 0, type: 'directory', path: '/storage/test' }, { name: 'asdf', size: 170, type: 'directory', path: '/storage/test/asdf' }, { name: '2.txt', size: 0, type: 'file', path: '/storage/test/asdf/2.txt' }] There could be any number of arbitrary path's, this is the result of iterating through files and folders within a directory. What I'm trying to do is determine the 'root' node of these. Ultimately, this will be stored in mongodb and use materialized path to determine it's relationships. In this example, /storage/test is a root with no parent. /storage/test/asdf has the parent of /storage/test which is the parent to /storage/test/asdf/2.txt. My question is, how would you go about iterating through this array, to determine the parent's and associated children? Any help in the right direction would be great! Thank you

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• iPhone memory management: a release after setting self.someProperty = nil

  - by ddawber

  I am reading the LazyTableImages code that Apple have released and they do something to this effect (in an NSOperation subclass): - (void)dealloc { [myProperty release]; [myProperty2 release]; } - (void)main { // // Parse operation undertaken here // self.myProperty = nil; self.myProperty2 = nil; } My thinking is that they do this in case dealloc is called before setting properties to nil. Is my thinking correct here? Are the releases unnecessary, as self.myProperty = nil effectively releases myProperty? One thing I have noticed in this code is that they don't release all retained objects in dealloc, only some of them, which is really the cause for my confusion. Cheers

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• simple obj-c naming question

  - by Highstead

  This question is more to figure out how to look up classes and objects in objective-c but i lack the knowledge to figure out how to look this up so i pose the question here. In .Net if i had a MyObject.MyValue the MyValue would be called a property, and I could look this up in MSDN. In java i would check the javadocs online (and that property would have to be a value). With objective-c that is called a ? and if i wanted to look it up i would look where? Example: //Object.??? UIImage.backgroundColor = [UIColor blueColor];

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• Hibernate Hql find result size for paginator

  - by KCore

  Hi, I need to add paginator for my Hibernate application. I applied it to some of my database operations which I perform using Criteria by setting Projection.count().This is working fine. But when I use hql to query, I can't seem to get and efficient method to get the result count. If I do query.list().size() it takes lot of time and I think hibernate does load all the objects in memory. Can anyone please suggest an efficient method to retrieve the result count when using hql?

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