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• SQL Injection with Plain-Vanilla NHibernate

  - by James D

  Hello, Plain-vanilla NHibernate setup, eg, no fluent NHibernate, no HQL, nothing except domain objects and NHibernate mapping files. I load objects via: _lightSabers = session.CreateCriteria(typeof(LightSaber)).List<LightSaber>(); I apply raw user input directly to one property on the "LightSaber" class: myLightSaber.NameTag = "Raw malicious text from user"; I then save the LightSaber: session.SaveOrUpdate(myLightSaber); Everything I've seen says that yes, under this situation you are immune to SQL injection, because of the way NHibernate parameterizes and escapes the queries under the hood. However, I'm also a relative NHibernate beginner so I wanted to double-check. *waves hand* these aren't the droids you're looking for. Thanks!

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• Django : json serialize a queryset which uses defer() or only()

  - by PlanetUnknown

  Now I've been using json serializer and it works great. I had to modify my queries where I started using the only() & defer() filters, like so - retObj = OBJModel.objects.defer("create_dt").filter(loged_in_dt__gte=dtStart) After I've done the above, suddenly the json serializer is returning empty fields - {"pk": 19047, "model": "OBJModel_deferred_create_dt", "fields": {}} If I remove the defer(), the serializer gives all the data correctly. import json from django.utils import simplejson from django.core import serializers json_serializer = serializers.get_serializer("json")() retObj = OBJModel.objects.defer("create_dt").filter(loged_in_dt__gte=dtStart) json_serializer.serialize(retObj, ensure_ascii=False) I've scratched my head on this for a while now. Any insight would be great. NOTE : I am using django 1.1

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• myth about factory pattern

  - by leiz

  This has bothered me for awhile, and I have no clues if this is a myth. It seems that a factory pattern can ease the pain of adding a dependency for a class. For example, in a book, it has something like this Suppose that you have a class named Order. Initially it did not depend on anything. Therefore you didn't bother using a factory to create Order objects and you just used plain new to instantiate the objects. However, you now have a requirement that Order has to be created in association with a Customer. There are million places you need to change to add this extra parameter. If only you had de?ned a factory for the Order class, you would have met the new requirement without the same pain. How is this not same pain as adding an extra parameter to the constructor? I mean you would still need to provide an extra argument for the factory and that is also used by million places, right?

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• Python equivalent of Java's compareTo()

  - by astay13

  I'm doing a project in Python (3.2) for which I need to compare user defined objects. I'm used to OOP in Java, where one would define a compareTo() method in the class that specifies the natural ordering of that class, as in the example below: public class Foo { int a, b; public Foo(int aa, int bb) { a = aa; b = bb; } public int compareTo(Foo that) { // return a negative number if this < that // return 0 if this == that // return a positive number if this > that if (this.a == that.a) return this.b - that.b; else return this.a - that.a; } } I'm fairly new to classes/objects in Python, so I'd like to know what is the "pythonic" way to define the natural ordering of a class?

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• setIncludesSubentities: in an NSFetchRequest is broken for entities across multiple persistent store

  - by SG

  Prior art which doesn't quite address this: http://stackoverflow.com/questions/1774359/core-data-migration-error-message-model-does-not-contain-configuration-xyz I have narrowed this down to a specific issue. It takes a minute to set up, though; please bear with me. The gist of the issue is that a persistentStoreCoordinator (apparently) cannot preserve the part of an object graph where a managedObject is marked as a subentity of another when they are stored in different files. Here goes... 1) I have 2 xcdatamodel files, each containing a single entity. In runtime, when the managed object model is constructed, I manually define one entity as subentity of another using setSubentities:. This is because defining subentities across multiple files in the editor is not supported yet. I then return the complete model with modelByMergingModels. //Works! [mainEntity setSubentities:canvasEntities]; NSLog(@"confirm %@ is super for %@", [[[canvasEntities lastObject] superentity] name], [[canvasEntities lastObject] name]); //Output: "confirm Note is super for Browser" 2) I have modified the persistentStoreCoordinator method so that it sets a different store for each entity. Technically, it uses configurations, and each entity has one and only one configuration defined. //Also works! for ( NSString *configName in [[HACanvasPluginManager shared].registeredCanvasTypes valueForKey:@"viewControllerClassName"] ) { storeUrl = [NSURL fileURLWithPath:[[self applicationDocumentsDirectory] stringByAppendingPathComponent:[configName stringByAppendingPathExtension:@"sqlite"]]]; //NSLog(@"entities for configuration '%@': %@", configName, [[[self managedObjectModel] entitiesForConfiguration:configName] valueForKey:@"name"]); //Output: "entities for configuration 'HATextCanvasController': (Note)" //Output: "entities for configuration 'HAWebCanvasController': (Browser)" if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:configName URL:storeUrl options:options error:&error]) //etc 3) I have a fetchRequest set for the parent entity, with setIncludesSubentities: and setAffectedStores: just to be sure we get both 1) and 2) covered. When inserting objects of either entity, they both are added to the context and they both are fetched by the fetchedResultsController and displayed in the tableView as expected. // Create the fetch request for the entity. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setEntity:entity]; [fetchRequest setIncludesSubentities:YES]; //NECESSARY to fetch all canvas types [fetchRequest setSortDescriptors:sortDescriptors]; [fetchRequest setFetchBatchSize:20]; // Set the batch size to a suitable number. [fetchRequest setAffectedStores:[[managedObjectContext persistentStoreCoordinator] persistentStores]]; [fetchRequest setReturnsObjectsAsFaults:NO]; Here is where it starts misbehaving: after closing and relaunching the app, ONLY THE PARENT ENTITY is fetched. If I change the entity of the request using setEntity: to the entity for 'Note', all notes are fetched. If I change it to the entity for 'Browser', all the browsers are fetched. Let me reiterate that during the run in which an object is first inserted into the context, it will appear in the list. It is only after save and relaunch that a fetch request fails to traverse the hierarchy. Therefore, I can only conclude that it is the storage of the inheritance that is the problem. Let's recap why: - Both entities can be created, inserted into the context, and viewed, so the model is working - Both entities can be fetched with a single request, so the inheritance is working - I can confirm that the files are being stored separately and objects are going into their appropriate stores, so saving is working - Launching the app with either entity set for the request works, so retrieval from the store is working - This also means that traversing different stores with the request is working - By using a single store instead of multiple, the problem goes away completely, so creating, storing, fetching, viewing etc is working correctly. This leaves only one culprit (to my mind): the inheritance I'm setting with setSubentities: is effective only for objects creating during the session. Either objects/entities are being stored stripped of the inheritance info, or entity inheritance as defined programmatically only applies to new instances, or both. Either of these is unacceptable. Either it's a bug or I am way, way off course. I have been at this every which way for two days; any insight is greatly appreciated. The current workaround - just using a single store - works completely, except it won't be future-proof in the event that I remove one of the models from the app etc. It also boggles the mind because I can't see why you would have all this infrastructure for storing across multiple stores and for setting affected stores in fetch requests if it by core definition (of setSubentities:) doesn't work.

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• How to implement a memory transaction scope in C#?

  - by theburningmonk

  Hi, we have a cache which I would like to put some transaction scopes around so that any process have to explicitly 'commit' the changes it wants to do to the cached objects and make it possible to rollback any changes when the process fails halfway as well. Right now, we're deep cloning the cached objects on get requests, it works but it's not a clean solution and involves a fair bit of maintenance too. I remember hearing about some MTS (memory transaction scope) solution on .NetRocks a while back but can't remember the name of it! Does anyone know of a good MTS framework out there? Alternatively, if I was to implement my own, are there any good guidelines/patterns on how to do this? Thanks,

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• How do I draw a proper parallelogram that can be animated on iPhone?

  - by Robert Kosara

  I'm trying to do something very simple: I need some parallelograms in my program. These are attached to other objects, all of which are UIViews. It's important that I be able to animate these, since the objects they are attached to can also be animated. I've figured out how to use the transform in UIView/CALayer to do this, but the problem is that these sheared UIViews don't look very nice: there is no anti-aliasing of the edges. Is there some other way to do this? I would like to use UIViews, since I also use them for user interaction and animation is so much easier than drawing by hand. I don't want to use OpenGL for this.

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• Tracking upstream svn changes with git-svn and github?

  - by Joseph Turian

  How do I track upstream SVN changes using git-svn and github? I used git-svn to convert an SVN repo to git on github: $ git svn clone -s http://svn.osqa.net/svnroot/osqa/ osqa $ cd osqa $ git remote add origin [email protected]:turian/osqa.git $ git push origin master I then made a few changes in my git repo, committed, and pushed to github. Now, I am on a new machine. I want to take upstream SVN changes, merge them with my github repo, and push them to my github repo. This documentation says: "If you ever lose your local copy, just run the import again with the same settings, and you’ll get another working directory with all the necessary SVN metainfo." So I did the following. But none of the commands work as desired. How do I track upstream SVN changes using git-svn and github? What am I doing wrong? $ git svn clone -s http://svn.osqa.net/svnroot/osqa/ osqa $ cd osqa $ git remote add origin [email protected]:turian/osqa.git $ git push origin master To [email protected]:turian/osqa.git ! [rejected] master -> master (non-fast forward) error: failed to push some refs to '[email protected]:turian/osqa.git' $ git pull remote: Counting objects: 21, done. remote: Compressing objects: 100% (17/17), done. remote: Total 17 (delta 7), reused 9 (delta 0) Unpacking objects: 100% (17/17), done. From [email protected]:turian/osqa * [new branch] master -> origin/master From [email protected]:turian/osqa * [new tag] master -> master You asked me to pull without telling me which branch you want to merge with, and 'branch.master.merge' in your configuration file does not tell me either. Please name which branch you want to merge on the command line and try again (e.g. 'git pull <repository> <refspec>'). See git-pull(1) for details on the refspec. ... $ /usr//lib/git-core/git-svn rebase warning: refname 'master' is ambiguous. First, rewinding head to replay your work on top of it... Applying: Added forum/management/commands/dumpsettings.py error: Ref refs/heads/master is at 6acd747f95aef6d9bce37f86798a32c14e04b82e but expected a7109d94d813b20c230a029ecd67801e6067a452 fatal: Cannot lock the ref 'refs/heads/master'. Could not move back to refs/heads/master rebase refs/remotes/trunk: command returned error: 1

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• qt in windows7 environment

  - by sneha

  Hello everyone, i am having problem with running an example from qt which uses win32 libraries when i compile i dnt get any errors but when i run it is not able to open the application (.exe) file in windows 7.but when i compile this example in windowsXP it works fine. can anyone let me know whether i need to change my .pro file inorder to get it worked under windows 7. PLease help me out.thanks in advance. here is my .pro file # ------------------------------------------------- # Project created by QtCreator 2010-04-16T11:45:43 # ------------------------------------------------- QT += network QT += xml QT += opengl TARGET = Application TEMPLATE = app SOURCES += main.cpp \ mainwindow.cpp \ Tools.cpp \ Objects.cpp HEADERS += mainwindow.h \ Tools.h\ Objects.h unix { OBJECTS_DIR = .obj MOC_DIR = .moc } # UNIX installation isEmpty(PREFIX):PREFIX = /usr/local unix { headers.path = $$PREFIX/include/ZIP headers.files = $$HEADERS target.path = $$PREFIX/lib INSTALLS += headers \ target } !mac:x11:LIBS += -ldns_sd win32:LIBS += -ldnssd LIBPATH = C:/Temp/mDNSResponder-107.6/mDNSWindows/DLL/Debug INCLUDEPATH += c:/Temp/mDNSResponder-107.6/mDNSShared

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• Tracking object entries when "playing" a Windows Enhanced Metafile

  - by lzcd

  One of my current projects requires that I work out what colours are being used in an EMF file. I have been able to successfully whip up a file parser in C# that notes all references to colours... but haven't had any luck tracking which objects are in use across the entire file so I can apart colours that are referenced from colours that are used to paint on screen. The older style WMF files are easy as the object library starts at zero and one can simply track each "Create Object" style command... but EMF files are proving to be trickier as there seems to be preexisting entries in the library (if the "Select Object" commands I'm seeing are to be believed). Would anyone be able to either enlighten me on how to track objects in the library correctly with EMF files... or suggest an easier alternative to work out which colours are actually being used in the file (as opposed to just being defined)?

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• Using a Loader for a string of QML

  - by Robbert

  In Qt 5.3 I've been using the Loader QML element for loading screens. Now I'm trying to load a string of QML dynamically. Qt.createQmlObject enables me to do so, but I can't seem to get the Loader element to play along. Seems like Loader only takes a URL (QUrl) or component (QQmlComponent), but Qt.createQmlObject creates an object (QObject). I'm new to QML, but from my understanding components are reusable elements, similar to classes, and objects are the instances of those classes. I thus can't seem to wrap my head around why Loader wouldn't work with objects. How can I show a loading screen while (asynchronously) parsing and initializing a string of QML? Example QML code: Item { Rectangle {id: content} Loader {id: loader} Component.onCompleted: { var obj = Qt.createQmlObject('import QtQuick 2.3; Rectangle {}', content); loader.source = obj; // Throws error. } }

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• Exception design: Custom exceptions reading data from file?

  - by User

  I have a method that reads data from a comma separated text file and constructs a list of entity objects, let's say customers. So it reads for example, Name Age Weight Then I take these data objects and pass them to a business layer that saves them to a database. Now the data in this file might be invalid, so I'm trying to figure out the best error handling design. For example, the text file might have character data in the Age field. Now my question is, should I throw an exception such as InvalidAgeException from the method reading the file data? And suppose there is length restriction on the Name field, so if the length is greater than max characters do I throw a NameTooLongException or just an InvalidNameException, or do I just accept it and wait until the business layer gets a hold of it and throw exceptions from there? (If you can point me to a good resource that would be good too)

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• Django Passing Custom Form Parameters to Formset

  - by Paolo Bergantino

  I have a Django Form that looks like this: class ServiceForm(forms.Form): option = forms.ModelChoiceField(queryset=ServiceOption.objects.none()) rate = forms.DecimalField(widget=custom_widgets.SmallField()) units = forms.IntegerField(min_value=1, widget=custom_widgets.SmallField()) def __init__(self, *args, **kwargs): affiliate = kwargs.pop('affiliate') super(ServiceForm, self).__init__(*args, **kwargs) self.fields["option"].queryset = ServiceOption.objects.filter(affiliate=affiliate) I call this form with something like this: form = ServiceForm(affiliate=request.affiliate) Where request.affiliate is the logged in user. This works as intended. My problem is that I now want to turn this single form into a formset. What I can't figure out is how I can pass the affiliate information to the individual forms when creating the formset. According to the docs to make a formset out of this I need to do something like this: ServiceFormSet = forms.formsets.formset_factory(ServiceForm, extra=3) And then I need to create it like this: formset = ServiceFormSet() Now how can I pass affiliate=request.affiliate to the individual forms this way?

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• Why won't this hit test fire a second time? wpf

  - by csciguy

  All, I have a main window that contains two custom objects (AnimatedCharacter). These objects are nothing but images. These images might contain transparent portions. One of these objects slightly overlaps the other object. There is a listener attached to the main window and is as follows. private void Window_MouseLeftButtonUp_1(object sender, MouseButtonEventArgs e) { Point pt = e.GetPosition((UIElement)sender); //store off the mouse pt hitPointMouse = pt; //clear the result list hitResultsSubList.Clear(); EllipseGeometry m_egHitArea = new EllipseGeometry(pt, 1, 1); VisualTreeHelper.HitTest(sender as Visual, HitTestFilterFuncNew, new HitTestResultCallback(HitTestCallback), new GeometryHitTestParameters(m_egHitArea)); //Check all sub items you have now hit if (hitResultsSubList.Count > 0) { CheckSubHitItems(hitResultsSubList); } } The idea is to filter out only a select group of items (called AnimatedCharacters). The hittest and filters are as follows public HitTestResultBehavior HitTestCallback(HitTestResult htrResult) { IntersectionDetail idDetail = ((GeometryHitTestResult)htrResult).IntersectionDetail; switch (idDetail) { case IntersectionDetail.FullyContains: return HitTestResultBehavior.Continue; case IntersectionDetail.Intersects: return HitTestResultBehavior.Continue; case IntersectionDetail.FullyInside: return HitTestResultBehavior.Continue; default: return HitTestResultBehavior.Stop; } } public HitTestFilterBehavior HitTestFilterFuncNew(DependencyObject potentialHitTestTarget) { if (potentialHitTestTarget.GetType() == typeof(AnimatedCharacter)) { hitResultsSubList.Add(potentialHitTestTarget as AnimatedCharacter); } return HitTestFilterBehavior.Continue; } This returns me back a list (called hitResultsSubList) that I attempt to then process further. I want to take everything in the hitResultsSubList and run a hit test on it again. This time, the hit test will be checking alpha levels on the particular animatedCharacter object. private void CheckSubHitItems(List<DependencyObject> hitResultsSub) { for(int i = 0; i<hitResultsSub.Count; i++) { hitResultsList.Clear(); AnimatedCharacter ac = hitResultsSub[i] as AnimatedCharacter; try { //DEBUGGER SKIPS THIS NEXT LINE EVERY SINGLE TIME. VisualTreeHelper.HitTest(ac, null, new HitTestResultCallback(hitCallBack), new PointHitTestParameters(hitPointMouse)); } catch (Exception e) { System.Diagnostics.Debug.WriteLine(e.StackTrace); } if (hitResultsList.Count > 0) { //do something here } } } Here is my problem now. The hit test in the second function (CheckSubHitItems) never gets called. There are definitely items (DependencyObjects of the type AnimatedCharacter) in the hitResultSub, but no matter what, the second hit test will not fire. I can walk the for loop fine, but when that line is hit, I get the following console statement. Step into: Stepping over non-user code 'System.MulticastDelegate.CtorClosed' No exceptions are thrown. Any help is appreciated.

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• Core-Data + AFNetworking + UI Updating (Responsiveness)

  - by Mustafa

  Here's the scenario: I'm writing a DownloadManager, that allows the user to download, pause, cancel, download all, and pause all. The DownloadManager is a singleton, and uses AFNetworking to download files. It has it's own private managed object context, so that user can freely use other parts of the application (by adding, editing, deleting) core-data objects. I have a core-data entity DownloadInfo that stores the download information i.e. fileURL, fileSize, bytesRead, etc. The DownloadManager updates the download progress in DownloadInfo (one for each file). I have a DownloadManagerViewController which uses NSFetchedResultsController to show the download status to the user. This download view controller is using the main managed object context. Now let's say that I have 20 files in the download queue. And let's say that only 3 concurrent downloads are allowed. The download manager should download the file, and show the download progress. Problem: The DownloadInfo objects are being updated by the DownloadManager at a very high rate. The DownloadManagerViewController (responsible for showing the download progress) is updating the list using NSFetchedResultsControllerDelegate methods. The result is that a lot is happening in the main queue and application has very poor responsiveness. How can I fix this? How can I make the application responsive, while showing the download progress? I don't know how else to communicate that the download status between DownloadManager and DownloadManagerViewController. Is there another/ a better way to do this? I don't want to use main managed object context in my DownloadManager, for reasons mentioned above. Note, that the DownloadManager is using AFNetworking which is handling the requests asynchronously, but eventually the DownloadInfo objects are updated in the main thread (as a result of the callback methods). Maybe there's a way to handle the downloads and status update operations in a background thread? but how? How will I communicate between the main thread and the background thread i.e. how will I tell the background thread to queue another file for download? Thanks.

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• Subclassing Satchmo's Category model, but then getting the error "'Manager' object has no attribute 'root_categories'"

  - by hellsgate

  I'm using Satchmo as part of a website I'm currently building. At the moment I'm trying add more functions to the Satchmo Category class, but obviously I'm not going to make any changes to the Satchmo files. So, I thought that subclassing the Category class would give me a new class which contains all the Satchmo Category properties and methods while allowing me to add my own. However, either Python subclassing doesn't work like that, or I am doing it wrong. Here is the code I'm using to subclass Category: from product.models import Category class MyCategory(Category): """ additional functions to pull data from the Satchmo store app """ One of the methods I can normally use from the Category class is: Category.objects.root_categories() however, when I try to access MyCategory.objects.root_categories() I get the following error: AttributeError: 'Manager' object has no attribute 'root_categories' Can anyone point me in the right direction for solving this?

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• How to write to the OpenGL Depth Buffer

  - by Mikepote

  I'm trying to implement an old-school technique where a rendered background image AND preset depth information is used to occlude other objects in the scene. So for instance if you have a picture of a room with some wires hanging from the ceiling in the foreground, these are given a shallow depth value in the depthmap, and when rendered correctly, allows the character to walk "behind" the wires but in front of other objects in the room. So far I've tried creating a depth texture using: glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, Image.GetWidth(), Image.GetHeight(), 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, pixels); Then just binding it to a quad and rendering that over the screen, but it doesnt write the depth values from the texture. I've also tried: glDrawPixels(Image.GetWidth(), Image.GetHeight(), GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, pixels); But this slows down my framerate to about 0.25 fps... I know that you can do this in a pixelshader by setting the gl_fragDepth to a value from the texture, but I wanted to know if I could achieve this with non-pixelshader enabled hardware?

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• linq to sql dynamic data modify object before insert and update

  - by Dan Tanner

  I'm using Dynamic Data and LINQ to SQL for some admin pages on a .NET 3.5 web app. All my admin tables a CreatedBy, CreatedDate, UpdatedBy, and UpdatedDate. I'm looking for a way to inject the setting of these properties before the objects are inserted and updated. I've seen an object_inserting hook if you have a linq to sql datasource in the web form, but I'm using dynamic data...is there an easy way to generically set that? And I've also looked at modifying each of the partial classes for my admin objects, but the closest hook I see is to implement the OnValidate method with the Insert action. Any suggestions? TIA.

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• Direct2D window black when not in focus

  - by Saul Rennison

  Hi all, I have a Direct2D window which paints fine when in focus; however, when focus moves to another window (same application or another), the entire window goes black. I pinned the issue down to the use of ID2D1HwndRenderTarget::Clear. This function is vital to my application as without it, painting becomes rather... weird. Is there a way an un-focused Direct2D window can paint as normal (note: WM_PAINT is being called as usual, as is Clear, BeginPaint, etc. all without error) Thanks in advance.

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• What should I do with syncobj in SQL Server

  - by hgulyan

  Hi. I run this script to search particular text in sys.columns and I get a lot of "dbo.syncobj_0x3934443438443332" this kind of result. SELECT c.name, s.name + '.' + o.name FROM sys.columns c INNER JOIN sys.objects o ON c.object_id=o.object_id INNER JOIN sys.schemas s ON o.schema_id=s.schema_id WHERE c.name LIKE '%text%' If I get it right, they are replication objects. Is it so? Can i just throw them away from my query just like o.name NOT LIKE '%syncobj%' or there's another way? Thank you.

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• Search over multiple fields

  - by schneck

  Hi there, I think I don't unterstand django-haystack properly: I have a data model containing several fields, and I would to have two of them searched: class UserProfile(models.Model): user = models.ForeignKey(User, unique=True, default=None) twitter_account = models.CharField(max_length=50, blank=False) My search index settings: class UserProfileIndex(SearchIndex): text = CharField(document=True, model_attr='user') twitter_account = CharField(model_attr='twitter_account') def get_queryset(self): """Used when the entire index for model is updated.""" return UserProfile.objects.all() But when I perform a search, only the field "username" is searched; "twitter_account" is ignored. When I select the Searchresults via dbshell, the objects contain the correct values for "user" and "twitter_account", but the result page shows a "no results": {% if query %} <h3>Results</h3> {% for result in page.object_list %} <p> <a href="{{ result.object.get_absolute_url }}">{{ result.object.id }}</a> </p> {% empty %} <p>No results</p> {% endfor %} {% endif %} Any ideas?

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• Lifetime issue of IDisposable unmanaged resources in a complex object graph?

  - by stakx

  This question is about dealing with unmanaged resources (COM interop) and making sure there won't be any resource leaks. I'd appreciate feedback on whether I seem to do things the right way. Background: Let's say I've got two classes: A class LimitedComResource which is a wrapper around a COM object (received via some API). There can only be a limited number of those COM objects, therefore my class implements the IDisposable interface which will be responsible for releasing a COM object when it's no longer needed. Objects of another type ManagedObject are temporarily created to perform some work on a LimitedComResource. They are not IDisposable. To summarize the above in a diagram, my classes might look like this: +---------------+ +--------------------+ | ManagedObject | <>------> | LimitedComResource | +---------------+ +--------------------+ | o IDisposable (I'll provide example code for these two classes in just a moment.) Question: Since my temporary ManagedObject objects are not disposable, I obviously have no control over how long they'll be around. However, in the meantime I might have Disposed the LimitedComObject that a ManagedObject is referring to. How can I make sure that a ManagedObject won't access a LimitedComResource that's no longer there? +---------------+ +--------------------+ | managedObject | <>------> | (dead object) | +---------------+ +--------------------+ I've currently implemented this with a mix of weak references and a flag in LimitedResource which signals whether an object has already been disposed. Is there any better way? Example code (what I've currently got): LimitedComResource: class LimitedComResource : IDisposable { private readonly IUnknown comObject; // <-- set in constructor ... void Dispose(bool notFromFinalizer) { if (!this.isDisposed) { Marshal.FinalReleaseComObject(comObject); } this.isDisposed = true; } internal bool isDisposed = false; } ManagedObject: class ManagedObject { private readonly WeakReference limitedComResource; // <-- set in constructor ... public void DoSomeWork() { if (!limitedComResource.IsAlive()) { throw new ObjectDisposedException(); // ^^^^^^^^^^^^^^^^^^^^^^^ // is there a more suitable exception class? } var ur = (LimitedComResource)limitedComResource.Target; if (ur.isDisposed) { throw new ObjectDisposedException(); } ... // <-- do something sensible here! } }

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• Base-camp Style Subdomains and IDs of Models

  - by Newy

  I have an app that has Basecamp-style subdomains, that is, I have Projects, Users, Apples and Oranges. The Users, Apples and Oranges are all keyed to a Project and only exist in the http://project.myapp.com. I added a project_id to Users, Apples and Oranges and everything works, except of course that the ids of those three objects increment globally, and throughout my app I lookup objects by that id. This doesn't seem like best practice. Should I instead do lookups by a secondary key? How does that affect efficiency? If there's a good blog post that covers this, would be wesome.

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• How to add text to path?

  - by Pritorian

  Hi all. Te question is how to add text to path element. For example, I have path: Path firstPath = new Path(); firstPath.Stroke = Brushes.Black; firstPath.StrokeThickness = 1; myCanvas.Children.Add(firstPath); LineGeometry firstLine = new LineGeometry(); firstPath.Data = firstLine; And somewhere I define line's Start and End point's. The path is binded to controls (for example - two ellipses) and when I drag one of them, the line is dynamically resized and moved to be pinned to both objects. And now I wand to add some text, that would fit to this line and follow it. Any recommendations how to do this?

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• Adding a generic image field onto a ModelForm in django

  - by Prairiedogg

  I have two models, Room and Image. Image is a generic model that can tack onto any other model. I want to give users a form to upload an image when they post information about a room. I've written code that works, but I'm afraid I've done it the hard way, and specifically in a way that violates DRY. Was hoping someone who's a little more familiar with django forms could point out where I've gone wrong. Update: I've tried to clarify why I chose this design in comments to the current answers. To summarize: I didn't simply put an ImageField on the Room model because I wanted more than one image associated with the Room model. I chose a generic Image model because I wanted to add images to several different models. The alternatives I considered were were multiple foreign keys on a single Image class, which seemed messy, or multiple Image classes, which I thought would clutter my schema. I didn't make this clear in my first post, so sorry about that. Seeing as none of the answers so far has addressed how to make this a little more DRY I did come up with my own solution which was to add the upload path as a class attribute on the image model and reference that every time it's needed. # Models class Image(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') image = models.ImageField(_('Image'), height_field='', width_field='', upload_to='uploads/images', max_length=200) class Room(models.Model): name = models.CharField(max_length=50) image_set = generic.GenericRelation('Image') # The form class AddRoomForm(forms.ModelForm): image_1 = forms.ImageField() class Meta: model = Room # The view def handle_uploaded_file(f): # DRY violation, I've already specified the upload path in the image model upload_suffix = join('uploads/images', f.name) upload_path = join(settings.MEDIA_ROOT, upload_suffix) destination = open(upload_path, 'wb+') for chunk in f.chunks(): destination.write(chunk) destination.close() return upload_suffix def add_room(request, apartment_id, form_class=AddRoomForm, template='apartments/add_room.html'): apartment = Apartment.objects.get(id=apartment_id) if request.method == 'POST': form = form_class(request.POST, request.FILES) if form.is_valid(): room = form.save() image_1 = form.cleaned_data['image_1'] # Instead of writing a special function to handle the image, # shouldn't I just be able to pass it straight into Image.objects.create # ...but it doesn't seem to work for some reason, wrong syntax perhaps? upload_path = handle_uploaded_file(image_1) image = Image.objects.create(content_object=room, image=upload_path) return HttpResponseRedirect(room.get_absolute_url()) else: form = form_class() context = {'form': form, } return direct_to_template(request, template, extra_context=context)

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