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• Message queue proxy in Python + Twisted

  - by gasper_k

  Hi, I want to implement a lightweight Message Queue proxy. It's job is to receive messages from a web application (PHP) and send them to the Message Queue server asynchronously. The reason for this proxy is that the MQ isn't always avaliable and is sometimes lagging, or even down, but I want to make sure the messages are delivered, and the web application returns immediately. So, PHP would send the message to the MQ proxy running on the same host. That proxy would save the messages to SQLite for persistence, in case of crashes. At the same time it would send the messages from SQLite to the MQ in batches when the connection is available, and delete them from SQLite. Now, the way I understand, there are these components in this service: message listener (listens to the messages from PHP and writes them to a Incoming Queue) DB flusher (reads messages from the Incoming Queue and saves them to a database; due to SQLite single-threadedness) MQ connection handler (keeps the connection to the MQ server online by reconnecting) message sender (collects messages from SQlite db and sends them to the MQ server, then removes them from db) I was thinking of using Twisted for #1 (TCPServer), but I'm having problem with integrating it with other points, which aren't event-driven. Intuition tells me that each of these points should be running in a separate thread, because all are IO-bound and independent of each other, but I could easily put them in a single thread. Even though, I couldn't find any good and clear (to me) examples on how to implement this worker thread aside of Twisted's main loop. The example I've started with is the chatserver.py, which uses service.Application and internet.TCPServer objects. If I start my own thread prior to creating TCPServer service, it runs a few times, but the it stops and never runs again. I'm not sure, why this is happening, but it's probably because I don't use threads with Twisted correctly. Any suggestions on how to implement a separate worker thread and keep Twisted? Do you have any alternative architectures in mind?

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• Laggy interface with NSSearchField hooked up to an NSArrayController via bindings

  - by Simone Manganelli

  So I've got an NSSearchField hooked up directly to an NSArrayController via bindings, attached to the filterPredicate, so that without any code, the user can just type in the NSSearchField and filter the list of objects in the NSArrayController presented to him in the interface (an NSCollectionView, to be specific). The NSSearchField is hooked up to provide live searching, so that the NSCollectionView is filtered instantly as the user types, not after waiting for a short period for the user to stop typing. However, the problem is that this makes the interface really laggy. Typing is delayed significantly, by 0.5-1 seconds, and it seems like the NSCollectionView is trying to animate each and every rearrangement of items for each portion of the search string that the user enters. What I'd like is for the searching to be live, but the typing in the search field to be fluid, and the results to filter as fast as possible. Is there a way to do this via bindings, or will I need to put in some custom code that triggers the filterPredicate on a separate thread? (Note that I've got a custom sorting algorithm set up on the NSArrayController, and removing it seems to help a bit with the laggyness, but not completely.)

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• Is saving to database just to get an ID a bad hack?

  - by Narsil

  I hope the title is not too confusing. I am trying to make folders with linq-to-sql objects' IDs. Actually I have to create folders before I should save them. I will use them to keep user uploaded files. As you can see I have to create the folder with the FileID before I can save it there. So I just save a record which will be edited or maybe deleted File newFile = new File(); ...//add some values to fields so they don't throw rule violations db.AddFile(newFile); db.Save(); System.IO.Directory.CreateDirectory("..Uploads/"+newFile.FileId.ToString()); After that I will have to edit some fields and save again. Of course user might stop upload and I would have to delete it. I know I can write a stored procedure to get the next available FileID but some other upload happening at the same time would get the same number. So they would write in same directory which is a thing I don't want. Should I go on with this, would there be some problems? Can you think of a better way?

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• accepts_nested_attributes with Model.update for multiple models

  - by Ohad

  Hi, I'm trying to follow http://railscasts.com/episodes/198-edit-multiple-individually but I would like to save objects which are nested (accepts_nested_attributes_for). I've added the following in my controller: def edit_multiple @people = Person.find(params[:person_ids], :include => [:parameters]) end def update_multiple keys = params[:people].keys if keys.empty? flash[:error] = "Please select at least one person" redirect_to :back and return end values = keys.map {|k| params[:people][k]} @people = Person.update(keys,values).reject { |h| h.errors.empty? } if @people.empty? flash[:notice] = 'Updated people!' redirect_to person_path else redirect_to edit_multiple_path end end and in the view: <% form_tag update_multiple_people_path, :method => :post do %> <% for person in @people %> <% fields_for "people[]", host do |f| %> <%= f.error_messages :object_name => "person" %> <h3><%= h person.name %></h3> <% for parameter in person.parameters %> <% f.fields_for "person_parameters[]", parameter do |builder| -%> <%= render "common/parameters", :f => builder %> <% end -%> <% end -%> <p><%= link_to_add_fields "Add a parameter", f, :person_parameters, "common/parameters" %></p> <% end %> <% end %> <p><%= submit_tag "Edit these Parameter(s)" %></p> <% end %> but I'm always getting a mistmatch - e.g. ActiveRecord::AssociationTypeMismatch and Parameter(#70341811965140) expected, got Array(#70341874300460) Thanks!

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• How to use SendMessage to another form in same app

  - by Robert Frank

  I've been trying to get this to work for some time now and can't figure it out. Probably obvious once you know it. I simply want a non-modal form (or perhaps an instantiated non-TForm class) to send a message to the application's main form. I can make the main form send a message to itself and receive (announcing with a beep) But, I can't seem to have other objects send messages to the main form. I'm using WM_MY_MESSAGE = WM_APP + 200; What should the first argument of the SendMessage be to send a message to the main form? Even sending it to Application.MainForm.Handle doesn't seem to work. The reason I need to do this is that the modal form has a slider that another form (#2) needs to know when it changes. Notifying the other form via a callback procedure was making it sluggish as form #2 did some work before returning from the call. Is having a modal form send a windows message to the main form a reasonable way to avoid this?

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• PHP: MVC and Model

  - by Pirkka

  Hello I`ve been wondering this one thing about creating models. If I make for example Page model. Is it the both: It can retrieve one row from the table or all the rows. Somehow Im mixing the objects and the database. I have thought it like this: I would have to make a Page-class that would represent one row in the table. It also would have all the basic CRUD-methods. Then I would have to do a Pages-class (somekind of collection) that would retrieve rows from the table and instantiate a Page object from each row. Is this kind of weird? If someone could explain to me the idea of model throughout.. Im again confused. Maybe Im thinking the whole OOP too difficult.. And by the way this forum is great. Hopefully people will just understand my problems. Heh. I was a long time procedural style programmer and now in 3 months I have dived into OOP and MVC and PHP frameworks and I just get more excited day by day when I explore this stuff!

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• VSTO Word ContentControls, Y U No have Name property?

  - by System.Cats.Lol

  When you add a VSTO (not Word native) content control, you specify the name: controls.AddContentControl(wordRange, "foo", wdType); Where controls is the VSTO (extended) Document.Controls collection. You can later look up the control by name: ContentControl myContentControl = controls["foo"]; So why in the world is there no Name property for ContentControl? (or ContentControlBase, or any of the other derivatives). I'm implementing a wrapper class for the Document.Controls property that lets you add or iterate the content controls. When iterating the underlying Document.Controls, there's no way to look up the name of each control. (We need it to return an instance of our ContentControl wrapper). So currently I'm doing this in our ContentControls wrapper class: public IEnumerator<IContentControl> GetEnumerator() { System.Collections.IEnumerator en = this.wordControls.GetEnumerator(); while (en.MoveNext()) { // VSTO Document.Controls includes all managed controls, not just // VSTO ContentControls; return only those. if (en.Current is Microsoft.Office.Tools.Word.ContentControl) { // The control's name isn't stored with the control, only when it was added, // so use a placeholder name for the wrapper. yield return new ContentControl("Unknown", (Microsoft.Office.Tools.Word.ContentControl)en.Current); } } } I'd prefer to not have to resort to keeping a map of names-to-wrapper-objects in our ContentControls object. Can anyone tell me how to get the control's name (the name parameter that was passed to Controls.Add()?

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• UriMapper Problem

  - by jsop

  I have the following xaml (nonessential markup removed in the interest of brevity): <navigation:Frame x:Name="ContentFrame" > <navigation:Frame.UriMapper> <uriMapper:UriMapper> <uriMapper:UriMapping Uri="/{pageName}" MappedUri="/Views/{pageName}.xaml"/> <uriMapper:UriMapping Uri="/FMChart/{metricID}/{orgID}" MappedUri="/Views/FMChart.xaml?metricID={metricID}&orgID={orgID}"/> </navigation:Frame.UriMapper> </navigation:Frame.UriMapper> </navigation:Frame> I'm creating the HyperLinkButton objects dynamically (in code), like so: int metricID = 1; int orgID = 1; HyperlinkButton button = new HyperlinkButton(); button.Name = Guid.NewGuid().ToString(); button.TargetName = "ContentFrame"; // this string doesn't work string url = string.Format("/FMChart/{0}/{1}", metricID, orgID); button.NavigateUri = new Uri(url, UriKind.Relative); When I click the bbutton, the browser renders a blank page, and eventually presents me with a REALLY long stack trace (InvalidOperation exception). If I take the parameters out of th indicated line: string url = "/FMChart"; ...it works as expected (brings up the desired page). I've also tried the following strings: /FMChart/{0}&{1} /FMChart/{0}& amp;{1} What am I doing wrong?

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• Django formset doesn't validate

  - by tsoporan

  Hello, I am trying to save a formset but it seems to be bypassing is_valid() even though there are required fields. To test this I have a simple form: class AlbumForm(forms.Form): name = forms.CharField(required=True) The view: @login_required def add_album(request, artist): artist = Artist.objects.get(slug__iexact=artist) AlbumFormSet = formset_factory(AlbumForm) if request.method == 'POST': formset = AlbumFormSet(request.POST, request.FILES) if formset.is_valid(): return HttpResponse('worked') else: formset = AlbumFormSet() return render_to_response('submissions/addalbum.html', { 'artist': artist, 'formset': formset, }, context_instance=RequestContext(request)) And the template: <form action="" method="post" enctype="multipart/form-data">{% csrf_token %} {{ formset.management_form }} {% for form in formset.forms %} <ul class="addalbumlist"> {% for field in form %} <li> {{ field.label_tag }} {{ field }} {{ field.errors }} </li> {% endfor %} </ul> {% endfor %} <div class="inpwrap"> <input type="button" value="add another"> <input type="submit" value="add"> </div> </form> What ends up happening is I hit "add" without entering a name then HttpResponse('worked') get's called seemingly assuming it's a valid form. I might be missing something here, but I can't see what's wrong. What I want to happen is, just like any other form if the field is required to spit out an error if its not filled in. Any ideas?

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• Django generic relation field reports that all() is getting unexpected keyword argument when no args

  - by Joshua

  I have a model which can be attached to to other models. class Attachable(models.Model): content_type = models.ForeignKey(ContentType) object_pk = models.TextField() content_object = generic.GenericForeignKey(ct_field="content_type", fk_field="object_pk") class Meta: abstract = True class Flag(Attachable): user = models.ForeignKey(User) flag = models.SlugField() timestamp = models.DateTimeField() I'm creating a generic relationship to this model in another model. flags = generic.GenericRelation(Flag) I try to get objects from this generic relation like so: self.flags.all() This results in the following exception: >>> obj.flags.all() Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 105, in all return self.get_query_set() File "/usr/local/lib/python2.6/dist-packages/django/contrib/contenttypes/generic.py", line 252, in get_query_set return superclass.get_query_set(self).filter(**query) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 498, in filter return self._filter_or_exclude(False, *args, **kwargs) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 516, in _filter_or_exclude clone.query.add_q(Q(*args, **kwargs)) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1675, in add_q can_reuse=used_aliases) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1569, in add_filter negate=negate, process_extras=process_extras) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1737, in setup_joins "Choices are: %s" % (name, ", ".join(names))) FieldError: Cannot resolve keyword 'object_id' into field. Choices are: content_type, flag, id, nestablecomment, object_pk, timestamp, user >>> obj.flags.all(object_pk=obj.pk) Traceback (most recent call last): File "<console>", line 1, in <module> TypeError: all() got an unexpected keyword argument 'object_pk' What have I done wrong?

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• Using Doctrine to abstract CRUD operations

  - by TomWilsonFL

  This has bothered me for quite a while, but now it is necessity that I find the answer. We are working on quite a large project using CodeIgniter plus Doctrine. Our application has a front end and also an admin area for the company to check/change/delete data. When we designed the front end, we simply consumed most of the Doctrine code right in the controller: //In semi-pseudocode function register() { $data = get_post_data(); if (count($data) && isValid($data)) { $U = new User(); $U->fromArray($data); $U->save(); $C = new Customer(); $C->fromArray($data); $C->user_id = $U->id; $C->save(); redirect_to_next_step(); } } Obviously when we went to do the admin views code duplication began and considering we were in a "get it DONE" mode so it now stinks with code bloat. I have moved a lot of functionality (business logic) into the model using model methods, but the basic CRUD does not fit there. I was going to attempt to place the CRUD into static methods, i.e. Customer::save($array) [would perform both insert and update depending on if prikey is present in array], Customer::delete($id), Customer::getObj($id = false) [if false, get all data]. This is going to become painful though for 32 model objects (and growing). Also, at times models need to interact (as the interaction above between user data and customer data), which can't be done in a static method without breaking encapsulation. I envision adding another layer to this (exposing web services), so knowing there are going to be 3 "controllers" at some point I need to encapsulate this CRUD somewhere (obviously), but are static methods the way to go, or is there another road? Your input is much appreciated.

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• JSF Float Conversion

  - by Phill Sacre

  I'm using JSF 1.2 with IceFaces 1.8 in a project here. I have a page which is basically a big edit grid for a whole bunch of floating-point number fields. This is implemented with inputText fields on the page pointing at a value object with primitive float types Now, as a new requirement sees some of the fields be nullable, I wanted to change the value object to use Float objects rather than primitive types. I didn't think I'd need to do anything to the page to accomodate this. However, when I make the change I get the following error: /pages/page.xhtml @79,14 value="#{row.targetValue}": java.lang.IllegalArgumentException: argument type mismatch And /pages/page.xhtml @79,14 value="#{row.targetValue}": java.lang.IllegalArgumentException: java.lang.ClassCastException@1449aa1 The page looks like this: <ice:inputText value="#{row.targetValue}" size="4"> <f:convertNumber pattern="###.#" /> </ice:inputText> I've also tried adding in <f:convert convertId="javax.faces.Float" /> in there as well but that doesn't seem to work either! Neither does changing the value object types to Double. I'm sure I'm probably missing something really simple but I've been staring at this for a while now and no answers are immediately obvious!

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• Object addSubview only works in viewDidLoad

  - by DecodingSand

  Hi, I'm new to iPhone dev and need some help with adding subViews. I have a reusable object that I made that is stored in a separate .h .m and xib file. I would like to use this object in my main project's view controller. I have included the header and the assignment of the object generates no errors. I am able to load the object into my main project but can only do things with it inside my viewDidLoad method. I intend to have a few of these objects on my screen and am looking fora solution that is more robust then just hard wiring up multiple copies of the shape object. As soon as I try to access the object outside of the viewDidLoad it produces a variable unknown error - first use in this function. Here is my viewDidLoad method: shapeViewController *shapeView = [[shapeViewController alloc] initWithNibName:@"shapeViewController" bundle:nil]; [self.view addSubview: shapeView.view]; // This is the problem line // This code works changes the display on the shape object [shapeView updateDisplay:@"123456"]; ---- but the same code outside of the viewDidLoad generates the error. So to sum up, everything works except when I try to access the shapeView object in the rest of the methods. Thanks in advance

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• Elegant way of parsing Data files for Simulation

  - by sc_ray

  I am working on this project where I need to read in a lot of data from .dat files and use the data to perform simulations. The data in my .dat file looks as follows: DeviceID InteractingDeviceID InteractionStartTime InteractionEndTime 1 2 1101 1105 1,2 1101 and 1105 are tab delimited and it means Device 1 interacted with Device 2 at 1101 ms and ended the interaction at 1105ms. I have a trace data sets that compile thousands of such interactions and my job is to analyze these interactions. The first step is to parse the file. The language of choice is C++. The approach I was thinking of taking was to read the file, for every line that's read create a Device Object. This Device object will contain the property DeviceId and an array/vector of structs, that will contain a list of all the devices the given DeviceId interacted with over the course of the simulation.The struct will contain the Interacting Device Id, Interaction Start Time and Interaction End Time. I have a two fold question here: Is my approach correct? If I am on the right track, how do I rapidly parse these tab delimited data files and create Device objects without excessive memory overhead using C++? A push in the right direction will be much appreciated. Thanks

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• Getting a nicely formatted timestamp without lots of overhead?

  - by Brad Hein

  In my app I have a textView which contains real-time messages from my app, as things happen, messages get printed to this text box. Each message is time-stamped with HH:MM:SS. Up to now, I had also been chasing what seemed to be a memory leak, but as it turns out, it's just my time-stamp formatting method (see below), It apparently produces thousands of objects that later get gc'd. For 1-10 messages per second, I was seeing 500k-2MB of garbage collected every second by the GC while this method was in place. After removing it, no more garbage problem (its back to a nice interval of about 30 seconds, and only a few k of junk typically) So I'm looking for a new, more lightweight method for producing a HH:MM:SS timestamp string :) Old code: /** * Returns a string containing the current time stamp. * @return - a string. */ public static String currentTimeStamp() { String ret = ""; Date d = new Date(); SimpleDateFormat timeStampFormatter = new SimpleDateFormat("hh:mm:ss"); ret = timeStampFormatter.format(d); return ret; }

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• How do I simulate "In" using Linq2Sql

  - by flipdoubt

  I often find myself with a list of disconnected Linq2Sql objects or keys that I need to re-select from a Linq2Sql data-context to update or delete in the database. If this were SQL, I would use IN in the SQL WHERE clause, but I am stuck with what to do in Linq2Sql. Here is a sample of what I would like to write: public void MarkValidated(IList<int> idsToValidate) { using(_Db.NewSession()) // Instatiates new DataContext { // ThatAreIn <- this is where I am stuck var items = _Db.Items.ThatAreIn(idsToValidate).ToList(); foreach(var item in items) item.Validated = DateTime.Now; _Db.SubmitChanges(); } // Disposes of DataContext } Or: public void DeleteItems(IList<int> idsToDelete) { using(_Db.NewSession()) // Instatiates new DataContext { // ThatAreIn <- this is where I am stuck var items = _Db.Items.ThatAreIn(idsToValidate); _Db.Items.DeleteAllOnSubmit(items); _Db.SubmitChanges(); } // Disposes of DataContext } Can I get this done in one trip to the database? If so, how? Is it possible to send all those ints to the database as a list of parameters and is that more efficient than doing a foreach over the list to select each item one at a time?

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• ASP.NET MVC application architecture "guidelines"

  - by Joe Future

  I'm looking for some feedback on my ASP.NET MVC based CMS application architecture. Domain Model - depends on nothing but the System classes to define types. For now, mostly anemic. Repository Layer - abstracted data access, only called by the services layer Services Layer - performs business logic on domain models. Exposes view models to the controllers. ViewModelMapper - service that translates back and forth between view models and domain models Controllers - super thin "traffic cop" style functionality that interacts with the service layer and only talks in terms of view models, never domain models My domain model is mostly used as data transfer (DTO) objects and has minimal logic at the moment. I'm finding this is nice because it depends on nothing (not even classes in the services layer). The services layer is a bit tricky... I only want the controllers to have access to viewmodels for ease of GUI programming. However, some of the services need to talk to each other. For example, I have an eventing service that notifies other listener services when content is tagged, when blog posts are created, etc. Currently, the methods that take domain models as inputs or return them are marked internal so they can't be used by the controllers. Sounds like overkill? Not enough abstraction? I'm mainly doing this as a learning exercise in being strict about architecture, not for an actual product, so please no feedback along the lines of "right depends on what you want to do". thanks! Jason

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• foreignkey problem

  - by realshadow

  Hey, Imagine you have this model: class Category(models.Model): node_id = models.IntegerField(primary_key = True) type_id = models.IntegerField(max_length = 20) parent_id = models.IntegerField(max_length = 20) sort_order = models.IntegerField(max_length = 20) name = models.CharField(max_length = 45) lft = models.IntegerField(max_length = 20) rgt = models.IntegerField(max_length = 20) depth = models.IntegerField(max_length = 20) added_on = models.DateTimeField(auto_now = True) updated_on = models.DateTimeField(auto_now = True) status = models.IntegerField(max_length = 20) node = models.ForeignKey(Category_info, verbose_name = 'Category_info', to_field = 'node_id' The important part is the foreignkey. When I try: Category.objects.filter(type_id = 15, parent_id = offset, status = 1) I get an error that get returned more than category, which is fine, because it is supposed to return more than one. But I want to filter the results trough another field, which would be type id (from the second Model) Here it is: class Category_info(models.Model): objtree_label_id = models.AutoField(primary_key = True) node_id = models.IntegerField(unique = True) language_id = models.IntegerField() label = models.CharField(max_length = 255) type_id = models.IntegerField() The type_id can be any number from 1 - 5. I am desparately trying to get only one result where the type_id would be number 1. Here is what I want in sql: SELECT c.*, ci.* FROM category c JOIN category_info ci ON (c.node_id = ci.node_id) WHERE c.type_id = 15 AND c.parent_id = 50 AND ci.type_id = 1 Any help is GREATLY appreciated. Regards

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• Suggested (simple) approach for drawing large numbers of visual elements in WPF?

  - by Ender

  I'm writing an interface that features a large (~50000px width) "canvas"-type area that is used to display a lot of data in a fairly novel way. This involves lots of lines, rectangles, and text. The user can scroll around to explore the entire canvas. At the moment I'm just using a standard Canvas panel with various Shapes placed on it. This is nice and easy to do: construct a shape, assign some coordinates, and attach it to the Canvas. Unfortunately, it's pretty slow (to construct the children, not to do the actual rendering). I've looked into some alternatives, it's a bit intimidating. I don't need anything fancy - just the ability to efficiently construct and place objects in a coordinate plane. If all I get are lines, colored rectangles, and text, I'll be happy. Do I need Geometry instances inside of Geometry Groups inside of GeometryDrawings inside of some Panel container? Note: I'd like to include text and graphics (i.e. colored rectangles) in the same space, if possible.

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• Giving another object a NSManagedObject

  - by Wayfarer

  Alright, so I'm running into an issue with my code. What I have done is subclassed UIButton so I can give it some more infomormation that pertain to my code. I have been able to create the buttons and they work great. Capiche. However, one of the things I want my subclass to hold is a reference to a NSMangedObject. I have this code in my header file: @interface ButtonSubclass : UIButton { NSManagedObjectContext *context; NSManagedObject *player; } @property (nonatomic, retain) NSManagedObject *player; @property (nonatomic, retain) NSManagedObjectContext *context; - (id)initWithFrame:(CGRect)frame andTitle:(NSString*)title; //- (void)setPlayer:(NSManagedObject *)aPlayer; @end As you can see, it has a instance variable to the NSMangedobject I want it to hold (as well as the Context). But for the life of me, I can't get it to hold that NSManagedObject. I run both the @synthesize methods in the Implementation file. @synthesize context; @synthesize player; So I'm not sure what I'm doing wrong. This is how I create my button: ButtonSubclass *playerButton = [[ButtonSubclass alloc] initWithFrame:frame andTitle:@"20"]; //works playerButton.context = self.context; //works playerButton.player = [players objectAtIndex:i]; //FAILS And I have initilaized the players array earlier, where I get the objects. Another weird thing is that when it gets to this spot in the code, the app crashes (woot) and the the console output stops. It doesn't give me any error, and notification at all that the app has crashed. It just... stops. So I don't even know what the error is that is crashing the code, besides it has to do with that line up there setting the "player" variable. Thoughts and ideas? I'd love your wisdom!

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• How much effort do you have to put in to get gains from using SSE?

  - by John

  Case One Say you have a little class: class Point3D { private: float x,y,z; public: operator+=() ...etc }; Point3D &Point3D::operator+=(Point3D &other) { this->x += other.x; this->y += other.y; this->z += other.z; } A naive use of SSE would simply replace these function bodies with using a few intrinsics. But would we expect this to make much difference? MMX used to involve costly state cahnges IIRC, does SSE or are they just like other instructions? And even if there's no direct "use SSE" overhead, would moving the values into SSE registers and back out again really make it any faster? Case Two Instead, you're working with a less OO-based code base. Rather than an array/vector of Point3D objects, you simply have a big array of floats: float coordinateData[NUM_POINTS*3]; void add(int i,int j) //yes it's unsafe, no overlap check... example only { for (int x=0;x<3;++x) { coordinateData[i*3+x] += coordinateData[j*3+x]; } } What about use of SSE here? Any better? In conclusion Is trying to optimise single vector operations using SSE actually worthwhile, or is it really only valuable when doing bulk operations?

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• Writing good tests for Django applications

  - by Ludwik Trammer

  I've never written any tests in my life, but I'd like to start writing tests for my Django projects. I've read some articles about tests and decided to try to write some tests for an extremely simple Django app or a start. The app has two views (a list view, and a detail view) and a model with four fields: class News(models.Model): title = models.CharField(max_length=250) content = models.TextField() pub_date = models.DateTimeField(default=datetime.datetime.now) slug = models.SlugField(unique=True) I would like to show you my tests.py file and ask: Does it make sense? Am I even testing for the right things? Are there best practices I'm not following, and you could point me to? my tests.py (it contains 11 tests): # -*- coding: utf-8 -*- from django.test import TestCase from django.test.client import Client from django.core.urlresolvers import reverse import datetime from someproject.myapp.models import News class viewTest(TestCase): def setUp(self): self.test_title = u'Test title: bareksc' self.test_content = u'This is a content 156' self.test_slug = u'test-title-bareksc' self.test_pub_date = datetime.datetime.today() self.test_item = News.objects.create( title=self.test_title, content=self.test_content, slug=self.test_slug, pub_date=self.test_pub_date, ) client = Client() self.response_detail = client.get(self.test_item.get_absolute_url()) self.response_index = client.get(reverse('the-list-view')) def test_detail_status_code(self): """ HTTP status code for the detail view """ self.failUnlessEqual(self.response_detail.status_code, 200) def test_list_status_code(self): """ HTTP status code for the list view """ self.failUnlessEqual(self.response_index.status_code, 200) def test_list_numer_of_items(self): self.failUnlessEqual(len(self.response_index.context['object_list']), 1) def test_detail_title(self): self.failUnlessEqual(self.response_detail.context['object'].title, self.test_title) def test_list_title(self): self.failUnlessEqual(self.response_index.context['object_list'][0].title, self.test_title) def test_detail_content(self): self.failUnlessEqual(self.response_detail.context['object'].content, self.test_content) def test_list_content(self): self.failUnlessEqual(self.response_index.context['object_list'][0].content, self.test_content) def test_detail_slug(self): self.failUnlessEqual(self.response_detail.context['object'].slug, self.test_slug) def test_list_slug(self): self.failUnlessEqual(self.response_index.context['object_list'][0].slug, self.test_slug) def test_detail_template(self): self.assertContains(self.response_detail, self.test_title) self.assertContains(self.response_detail, self.test_content) def test_list_template(self): self.assertContains(self.response_index, self.test_title)

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• Baffled by differences between WPF BitmapEncoders

  - by DanM

  I wrote a little utility class that saves BitmapSource objects to image files. The image files can be either bmp, jpeg, or png. Here is the code: public class BitmapProcessor { public void SaveAsBmp(BitmapSource bitmapSource, string path) { Save(bitmapSource, path, new BmpBitmapEncoder()); } public void SaveAsJpg(BitmapSource bitmapSource, string path) { Save(bitmapSource, path, new JpegBitmapEncoder()); } public void SaveAsPng(BitmapSource bitmapSource, string path) { Save(bitmapSource, path, new PngBitmapEncoder()); } private void Save(BitmapSource bitmapSource, string path, BitmapEncoder encoder) { using (var stream = new FileStream(path, FileMode.Create)) { encoder.Frames.Add(BitmapFrame.Create(bitmapSource)); encoder.Save(stream); } } } Each of the three Save methods work, but I get unexpected results with bmp and jpeg. Png is the only format that produces an exact reproduction of what I see if I show the BitmapSource on screen using a WPF Image control. Here are the results: BMP - too dark JPEG - too saturated PNG - correct Why am I getting completely different results for different file types? I should note that the BitmapSource in my example uses an alpha value of 0.1 (which is why it appears very desaturated), but it should be possible to show the resulting colors in any image format. I know if I take a screen capture using something like HyperSnap, it will look correct regardless of what file type I save to. Here's a HyperSnap screen capture saved as a bmp: As you can see, this isn't a problem, so there's definitely something strange about WPF's image encoders. Do I have a setting wrong? Am I missing something?

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• How do JVM's implicit memory barriers behave when chaining constructors

  - by Joonas Pulakka

  Referring to my earlier question on incompletely constructed objects, I have a second question. As Jon Skeet pointed out, there's an implicit memory barrier in the end of a constructor that makes sure that final fields are visible to all threads. But what if a constructor calls another constructor; is there such a memory barrier in the end of each of them, or only in one being called from outside? That is, when the "wrong" solution is: public class ThisEscape { public ThisEscape(EventSource source) { source.registerListener( new EventListener() { public void onEvent(Event e) { doSomething(e); } }); } } And the correct one would be a factory method version: public class SafeListener { private final EventListener listener; private SafeListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public static SafeListener newInstance(EventSource source) { SafeListener safe = new SafeListener(); source.registerListener(safe.listener); return safe; } } Would the following work too, or not? public class MyListener { private final EventListener Listener; private MyListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public MyListener(EventSource source) { this(); source.register(listener); } }

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• 500 Worker Threads, what kind of thread pool?

  - by Submerged

  I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } The code that is executing is really simple and basically just this class aThread extends Thread { public void run(){ while(true){ Thread.sleep(ONE_MINUTE); //Lots of computation every minute } } } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful! Well, the design is arguably flawed. The threads implement Genetic-Programming or GP, a type of learning algorithm. Each thread analyzes advanced trends makes predictions. If the thread ever completes, the learning is lost. That said, I was hoping that sleep() would allow me to share some of the resources while one thread isn't "learning"

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