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• More strict query yields more results?

  - by Mark

  I've got a query that looks like this affiliates = User.objects.annotate(referral_count=Count('referrals')).filter(referral_count__gt=0) But when I restrict it more by adding referrals__user__date_joined__gt=start_date to the filter, I get even higher referral counts. I'm trying to count the number of people a user has referred within a time period. The relevant model looks like this: class Profile(models.Model): user = models.ForeignKey(User, unique=True, related_name='profile') referred_by = models.ForeignKey(User, null=True, blank=True, related_name='referrals') In contrast, when I try it like this: affiliates = User.objects \ .exclude(referrals__user__date_joined__lte=sd, referrals__user__date_joined__gt=ed) \ .annotate(referral_count=Count('referrals')) \ .filter(referral_count__gt=0) The exclude statement seems to do nothing... the counts don't change (should be 0 if no referred users have joined within that time period, but it isn't).

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• How to keep historic details of modification in a database (Audit trail)?

  - by mada

  I'm a J2EE developer & we are using hibernate mapping with a PostgreSQL database. We have to keep track of any changes occurs in the database, in others words all previous & current values of any field should be saved. Each field can be any type (bytea, int, char...) With a simple table it is easy but we a graph of objects things are more difficult. So we have, speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that?

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• PHP 'instanceof' failing with class constant

  - by Nathan Loding

  I'm working on a framework that I'm trying to type as strongly as I possibly can. (I'm working within PHP and taking some of the ideas that I like from C# and trying to utilize them within this framework.) I'm creating a Collection class that is a collection of domain entities/objects. It's kinda modeled after the List<T> object in .Net. I've run into an obstacle that is preventing me from typing this class. If I have a UserCollection, it should only allow User objects into it. If I have a PostCollection, it should only allow Post objects. All Collections in this framework need to have certain basic functions, such as add, remove, iterate. I created an interface, but found that I couldn't do the following: interface ICollection { public function add($obj) } class PostCollection implements ICollection { public function add(Post $obj) {} } This broke it's compliance with the interface. But I can't have the interface strongly typed because then all Collections are of the same type. So I attempted the following: interface ICollection { public function add($obj) } abstract class Collection implements ICollection { const type = 'null'; } class PostCollection { const type = 'Post'; public function add($obj) { if(!($obj instanceof self::type)) { throw new UhOhException(); } } } When I attempt to run this code, I get syntax error, unexpected T_STRING, expecting T_VARIABLE or '$' on the instanceof statement. A little research into the issue and it looks like the root of the cause is that $obj instanceof self is valid to test against the class. It appears that PHP doesn't process the entire self::type constant statement in the expression. Adding parentheses around the self::type variable threw an error regarding an unexpected '('. An obvious workaround is to not make the type variable a constant. The expression $obj instanceof $this->type works just fine (if $type is declared as a variable, of course). I'm hoping that there's a way to avoid that, as I'd like to define the value as a constant to avoid any possible change in the variable later. Any thoughts on how I can achieve this, or have I take PHP to it's limit in this regard? Is there a way of "escaping" or encapsulating self::this so that PHP won't die when processing it?

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• what is this 'map' mean..in django

  - by zjm1126

  this is the code: def create(request, form_class=MapForm, template_name="maps/create.html"): map_form = form_class(request.POST or None) if map_form.is_valid(): map = map_form.save(commit=False) and the map_form is : class MapForm(forms.ModelForm): slug = forms.SlugField(max_length=20, help_text = _("a short version of the name consisting only of letters, numbers, underscores and hyphens."), #error_message = _("This value must contain only letters, numbers, underscores and hyphens.")) ) def clean_slug(self): if Map.objects.filter(slug__iexact=self.cleaned_data["slug"]).count() > 0: raise forms.ValidationError(_("A Map already exists with that slug.")) return self.cleaned_data["slug"].lower() def clean_name(self): if Map.objects.filter(name__iexact=self.cleaned_data["name"]).count() > 0: raise forms.ValidationError(_("A Map already exists with that name.")) return self.cleaned_data["name"] class Meta: model = Map fields = ('name', 'slug', 'description')

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• Library to encode/decode from json to java.util.Map?

  - by Oscar Reyes

  Does anyone knows a java library that could easily encode java Maps into json objects and the other way around?

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• SForceAPI : unable to find classes listed on API? (Account, Contact, etc)

  - by Firefox

  Hi, API referred : http://www.salesforce.com/us/developer/docs/api/index.htm subsection: reference-standard objects Client side details : partner.wsdl, Axis2 1.5, generated stubs using unpacked option (-u). I was hoping to find some basic objects like Account, Contact, etc (which were listed on above url) so that I can do something like - SObject[] sObjArray = queryResult.getRecords(); for(SObject sObj : sObjArray){ Account acc = [Account] sObj; } [used above approach successfully in another webservice - 'Zuora'] However, I could not find Account class in the generated classes. I guess I am into wrong approach, but atleast I should be finding the classes listed in the reference API. Please help.

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• Extracting Information from Images

  - by Khorkrak

  What are some fast and somewhat reliable ways to extract information about images? I've been tinkering with openCV and this seems so far to be the best route plus it has Python bindings. So to be more specific I'd like to determine what I can about what's in an image. So for example the haar face detection and full body detection classifiers are great - now I can tell that most likely there are faces and / or people in the image as well as about how many. okay - what else - how about whether there are any buildings and if so what do they seem to be - huts, office buildings etc? Is there sky visible, grass, trees and so forth. From what I've read about training classifiers to detect objects, it seems like a rather laborious process 10,000 or so wrong images and 5,000 or so correct samples to train a classifier. I'm hoping that there are some decent ones around already instead of having to do this all myself for a bunch of different objects - or is there some other way to go about this sort of thing?

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• Conceptual question about NSAutoreleasePools

  - by ryyst

  In my Cocoa program, wouldn't a really simple way of dealing with autoreleased objects be to just create a timer object inside the app delegate that calls the following method e.g. every 10 seconds: if (pool) { // Release & drain the current pool to free the memory. [pool release]; } // Create a new pool. pool = [[NSAutoreleasePool alloc] init]; The only problems I can imagine are: 1) If the above code runs in a separate thread, an object might get autoreleased between the release call to the old pool and the creation of the new pool - that seems highly unlikely though. 2) It's obviously not that efficient, because the pool might get released if there's nothing in it. Likewise, in the 10 second gap, many many objects might be autoreleased, causing the pool to grow a lot. Still, the above solution seems pretty suitable to small and simple projects. Why doesn't anybody use it? What's the best practice of using NSAutoreleasePools?

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• Can a variable bu used 2nd time after releasing it?

  - by Jakub

  Hello, I try to understand the memory management in ObjectiveC and still some things are a misery for me. I've got an instance variable: NSMutableArray *postResultsArray; when a button is clicked in the UI I create new array: self.postResultsArray = [NSMutableArray array]; then I add some objects to the array and when the whole operation is done I would like to release the array: [self.postResultsArray release]; (I assume that all the objects stoed in the array will be released along with the array). The problem appears when I click the button again and in the code I want to create the array again with: self.postResultsArray = [NSMutableArray array]; I get: [CFArray release]: message sent to deallocated instance 0x3d9e390 Can't I initialize the same instance variable for the second time? or maybe I should not release it? and if so, why? Thanks!

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• what is this 'content_type' mean..

  - by zjm1126

  content_type = ContentType.objects.get_for_model(Map) maps = maps.extra(select=SortedDict([ ('member_count', MEMBER_COUNT_SQL), ('topic_count', TOPIC_COUNT_SQL), ]), select_params=(content_type.id,)) and the ContentType is: class ContentType(models.Model): name = models.CharField(max_length=100) app_label = models.CharField(max_length=100) model = models.CharField(_('python model class name'), max_length=100) objects = ContentTypeManager() class Meta: verbose_name = _('content type') verbose_name_plural = _('content types') db_table = 'django_content_type' ordering = ('name',) unique_together = (('app_label', 'model'),) def __unicode__(self): return self.name def model_class(self): "Returns the Python model class for this type of content." from django.db import models return models.get_model(self.app_label, self.model) def get_object_for_this_type(self, **kwargs): """ Returns an object of this type for the keyword arguments given. Basically, this is a proxy around this object_type's get_object() model method. The ObjectNotExist exception, if thrown, will not be caught, so code that calls this method should catch it. """ return self.model_class()._default_manager.using(self._state.db).get(**kwargs) def natural_key(self): return (self.app_label, self.model) i want to know: what is the 'content_type' used for ??

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• How does Hibernate detect dirty state of an entity object?

  - by ???'Lenik

  Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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• Set sprite width or height without scaling it's children

  - by Gabi Barrientos

  I am trying to dynamically change the width and height of a Sprite object, which is a container for other similar Sprite objects. The container object automatically changes it's size according to the size of it's children, but when I change the position of the children objects, the size of the container stays the same and it's children appear to be placed outside of the container. I tried to solve this problem by using something like this: if (container.width < (child.x + child.width)) { container.width = (child.x + child.width); } but when I use this code, the container object's children are scaled. Is there a way to change the container's size without scaling it's children?

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• How to analyse contents of binary serialization stream?

  - by Tao

  I'm using binary serialization (BinaryFormatter) as a temporary mechanism to store state information in a file for a relatively complex (game) object structure; the files are coming out much larger than I expect, and my data structure includes recursive references - so I'm wondering whether the BinaryFormatter is actually storing multiple copies of the same objects, or whether my basic "number of objects and values I should have" arithmentic is way off-base, or where else the excessive size is coming from. Searching on stack overflow I was able to find the specification for Microsoft's binary remoting format: http://msdn.microsoft.com/en-us/library/cc236844(PROT.10).aspx What I can't find is any existing viewer that enables you to "peek" into the contents of a binaryformatter output file - get object counts and total bytes for different object types in the file, etc; I feel like this must be my "google-fu" failing me (what little I have) - can anyone help? This must have been done before, right??

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• Javascript instanceof & typeof in GWT (JSNI)

  - by rybz

  Hi, I've encountered an curious problem while trying to use some objects through JSNI in GWT. Let's say we have javscript file with the function defined: test.js: function test(arg){ var type = typeof(arg); if (arg instanceof Array) alert('Array'); if (arg instanceof Object) alert('Object'); if (arg instanceof String) alert('String'); } And the we want to call this function user JSNI: public static native void testx()/ *-{ $wnd.test( new Array(1, 2, 3) ); $wnd.test( [ 1, 2, 3 ] ); $wnd.test( {val:1} ); $wnd.test( "Some text" ); }-*/; The questions are: why instanceof instructions will always return false? why typeof will always return "object" ? how to pass these objects so that they were recognized properly?

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• Sharepoint: How to obtain the current site/web/list properly

  - by driAn

  Hi all What is the best way to obtain the current site/web/list ? Option 1 - Reusing existing objects SPSite site = SPContext.Current.Site; SPweb web = SPContext.Current.Web; SPList list = SPContext.Current.List; Option 2 - Creating new objects SPSite site = new SPSite(SPContext.Current.Site.ID); // dispose me SPweb web = site.OpenWeb(SPContext.Current.Web.ID); // dispose me SPList list = web.Lists[SPContext.Current.List.ID]; I experienced problems when using option 1 in some situations. Since then I chose the 2nd option and it worked fine so far. What is your opinion on this? I is generally better to go with option 2? Other suggestions?

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• Persisting a single UISearchBar instance across 4 separate UITableViews

  - by Jacob Relkin

  Hi fellas, I'm in the midst of an iPhone app that needs to have 4 separate UITableView objects sharing access to one UISearchBar in the first section and first row of the aforementioned UITableView objects. I have tried to offset the UITableView's frame by 44 pixels, then adding the search bar as a subview of my UIViewController's view. That works, but I cannot use the table index to scroll up to the search bar, since it is not a cell in the tableview. I need to have the search bar in the table view itself. My goal is to have the same UISearchBar in the first section of multiple tableviews. Thanks so much.

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• How to manually manage Core Data relationships when deleting

  - by Simon

  I have a Core Data entity, which contains a relationship to another entity. Under certain circumstances, I need to delete the managed objects in the relationship, and at other times no action needs to be taken. I have the Delete Rule on the entity is No Action because of this manual management. The problem I have is, where is the best place to enforce these rules? I cannot see any suitable messages to override on NSManagedObject (something that might notify the object it has been deleted and should clear up its relationships). I would rather not do it higher up in the application logic, because the entity objects can get deleted from array controllers and at different points in the applications, making it necessary to stuff relationship update code at all those levels.

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• how to search values in a dictionary that is assigned to a key for a PFObject without downloading all PFObjects of that class (iOS/Parse)

  - by mkc842

  Suppose I have a set of PFObjects (essentially dictionaries) of class "myObject". Objects of this class contain for key "myDictionary" a dictionary. "myDictionary", in turn, has a key "myKey" that I want to access and search for matches against "mySearchTerm". I don't want to download all myObject objects and then iterate through them to check myKey in each, because that would be very inefficient. I want to use a findObjects message to return just the matches. Is such a query possible? In other words, how can I search the values in a dictionary that is assigned to a key for a PFObject without downloading all PFObjects of that class? Here's what it might look like if there were a simple method for it, but I made up the containsKey part to clarify what I am contemplating: PFQuery *objectQuery = [PFQuery queryWithClassName:@"myObject"]; [objectQuery whereKey:@"myDictionary" ~containsKey~:@"myKey" equalTo:"mySearchTerm"];

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• Filtering data in an array.

  - by user276424

  Hi all, I have an array that has 30 date objects. The date objects are indexed in the array from the minimum date value to the maximum date value. What I would like to do is retrieve only 7 dates from the array. Out of the 7, the first one should be the minDate and the last should be the maxDate, with 5 dates in the middle. The 7 numbers should increment evenly from the minDate to the maxDate. How would I accomplish this? Hope I was clear. Thanks, Tonih

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• Cocoa : Remove Item from NSArrayController

  - by Holli

  I have a NSArrayController bound to a NSTableView. With this I have the typical Add/Remove buttons. While Adding an item is very straight forward (I call a method, create an object with default values and add it) I have problems deleting objects from the controller. I know I can do this the easy way when connecting the button with the remove action from the ArrayController. But this is not what I want. I need to remove the object manually because I have some additional code to process. Anway, removing objects seems far more complcated then I expected. It already tried: NSArray *items = [doToItemsArrayController selectedObjects]; [doToItemsArrayController removeSelectedObjects:items]; or NSIndexSet *iSet = [doToItemsArrayController selectionIndexes]; [doToItemsArrayController removeSelectionIndexes:iSet]; None of them seems to work. How do I remove the selected Object from an NSArrayController with Objective-C code?

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• Python: Repeat elements in a list comprehension?

  - by User

  I have the following list comprehension which returns a list of coordinate objects for each location. coordinate_list = [Coordinates(location.latitude, location.longitude) for location in locations] This works. Now suppose the location object has a number_of_times member. I want a list comprehension to generate n Coordinate objects where n is the number_of_times for the particular location. So if a location has number_of_times = 5 then the coordinates for that location will be repeated 5 times in the list. (Maybe this is a case for a for-loop but I'm curious if it can be done via list comprehensions)

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• How to persist non-trivial fields in Play Framework

  - by AlexR

  I am trying to persist complex objects using Ebeans in Play Framework (2.03). In particular, I've created a class that contains a field of type weka.classifier.Classifier (Weka is a popular machine learning library - see http://weka.sourceforge.net/doc/weka/classifiers/Classifier.html). Classifier implements Serializeable so I hoped that I can get away with something like @Entity @Table(name = "classifiers") public class ClassifierData extends Model { @Id public Long id; public Classifier classifier; } However, the Evolutions script suggests the following database structure: create table classifiers ( id bigint auto_increment not null, constraint pk_classifiers primary key (id)) ) In other words, it ignores the field of type Classifier. (The database is MySQL if it makes any difference) What should I do to store complex serializeable objects using Ebean/Evolutions/PlayFramework?

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• Setting up a "to-many" relationship value dependency for a transient Core Data attribute

  - by Greg Combs

  I've got a relatively complicated Core Data relationship structure and I'm trying to figure out how to set up value dependencies (or observations) across various to-many relationships. Let me start out with some basic info. I've got a classroom with students, assignments, and grades (students X assignments). For simplicity's sake, we don't really have to focus much on the assignments yet. StudentObj <--->> ScoreObj <<---> AssignmentObj Each ScoreObj has a to-one relation with the StudentObj and the AssignmentObj. ScoreObj has real attributes for the numerical grade, the turnInDate, and notes. AssignmentObj.scores is the set of Score objects for that assignment (N = all students). AssignmentObj has real attributes for name, dueDate, curveFunction, gradeWeight, and maxPoints. StudentObj.scores is the set of Score objects for that student (N = all assignments). StudentObj also has real attributes like name, studentID, email, etc. StudentObj has a transient (calculated, not stored) attribute called gradeTotal. This last item, gradeTotal, is the real pickle. it calculates the student's overall semester grade using the scores (ScoreObj) from all their assignments, their associated assignment gradeWeights, curves, and maxPoints, and various other things. This gradeTotal value is displayed in a table column, along with all the students and their individual assignment grades. Determining the value of gradeTotal is a relatively expensive operation, particularly with a large class, therefore I want to run it only when necessary. For simplicity's sake, I'm not storing that gradeTotal value in the core data model. I don't mind caching it somewhere, but I'm having a bitch of a time determining where and how to best update that cache. I need to run that calculation for each student whenever any value changes that affects their gradeTotal. If this were a simple to-one relationship, I know I could use something like keyPathsForValuesAffectingGradeTotal ... but it's more like a many-to-one-to-many relationship. Does anyone know of an elegant (and KVC correct) solution? I guess I could tear through all those score and assignment objects and tell them to register their students as observers. But this seems like a blunt force approach.

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• Django check for any exists for a query

  - by Hulk

  In django how to check whether any entry exists for a query sc=scorm.objects.filter(Header__id=qp.id) This was how it was done in php if(mysql_num_rows($resultn)) { } else { }

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• Iterating dictionary indexes in django templates

  - by unclaimedbaggage

  Hi folks...I have a dictionary with embedded objects, which looks something like this: notes = { 2009: [<Note: Test note>, <Note: Another test note>], 2010: [<Note: Third test note>, <Note: Fourth test note>], } I'm trying to access each of the note objects inside a django template, and having a helluva time navigating to them. In short, I'm not sure how to extract by index in django templating. Current template code is: <h3>Notes</h3> {% for year in notes %} {{ year }} # Works fine {% for note in notes.year %} {{ note }} # Returns blank {% endfor %} {% endfor %} If I replace {% for note in notes.year %} with {% for note in notes.2010 %} things work fine, but I need that '2010' to be dynamic. Any suggestions much appreciated.

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