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• Advice on designing and building distributed application to track vehicles

  - by dario-g

  I'm working on application for tracking vehicles. There will be about 10k or more vehicles. Each will be sending ~250bytes in each minute. Data contains gps location and everything from CAN Bus (every data that we can read from vehicle computer and dashboard). Data are sent by GSM/GPRS (using UDP protocol). Estimated rows with this data per day is ~2000k. I see there 3 main blocks. 1. Multithreaded Socket Server (MSS) - I have it. MSS stores received data to the queue (using NServiceBus). 2. Rule Processor Server (RPS) - this is core of this system. This block is responsible for parsing received data, storing in the database, processing rules, sending messages to Notifier Server (this will be sending e-mails/sms texts). Rule example. As I said between received bytes there will be information about current speed. When speed will be above 120 then: show alert in web application for specified users, send e-mail, send sms text. (There can be more than one instance of RPS). 3. Web application - allows reporting and defining rules by users, monitoring alerts, etc. I'm looking for advice how to design communication between RPS and Web application. Some questions: - Should Web application and RPS have separated databases or one central database will be enough? I have one domain model in web application. If there will be one central database then can I use the same model (objects) on RPS? So, how to send changed rules to RPS? I try to decouple this blocks as much as possible. I'm planning to create different instance of application for each client (each client will have separated database). One client will be have 10k vehicles, others only 100 vehicles.

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• Moq, a translator and an expression

  - by jeriley

  I'm working with an expression within a moq-ed "Get Service" and ran into a rather annoying issue. In order to get this test to run correctly and the get service to return what it should, there's a translator in between that takes what you've asked for, sends it off and gets what you -really- want. So, thinking this was easy I attempt this ... the fakelist is the TEntity objects (translated, used by the UI) and TEnterpriseObject is the actual persistance. mockGet.Setup(mock => mock.Get(It.IsAny<Expression<Func<TEnterpriseObject, bool>>>())).Returns( (Expression<Func<TEnterpriseObject, bool>> expression) => { var items = new List<TEnterpriseObject>(); var translator = (IEntityTranslator<TEntity, TEnterpriseObject>) ObjectFactory.GetInstance(typeof (IEntityTranslator<TEntity, TEnterpriseObject>)); fakeList.ForEach(fake => items.Add(translator.ToEnterpriseObject(fake))); items = items.Where(expression); var result = new List<TEnterpriseObject>(items); fakeList.Clear(); result.ForEach(item => translator.ToEntity(item)); return items; }); I'm getting the red squigglie under there items.where(expression) -- says it can't be infered from usage (confused between <Func<TEnterpriseObject,bool>> and <Func<TEnterpriseObject,int,bool>>) A far simpler version works great ... mockGet.Setup(mock => mock.Get(It.IsAny<Expression<Func<TEntity, bool>>>())).Returns( (Expression<Func<TEntity, bool>> expression) => fakeList.AsQueryable().Where(expression)); so I'm not sure what I'm missing... ideas?

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• Controlling the order of PicoContainer startup

  - by Trejkaz

  I have been tasked with doing some refactoring work on how we start up applications. Basically we have a bunch of console apps which were depending on the GUI application startup code, causing bogus dependencies which have kick-on effects for which libraries we need to ship, and which dependencies other modules need to declare. So I have written a simple startup framework where I basically just throw a bunch of Runnable objects into a list and then run them in order - and it works. But I was thinking - we already have PicoContainer in our project, so all these things that need to be run on startup could potentially be thrown into a PicoContainer, and if they implement Startable they will start... But in some cases we want to specify the ordering between them. For example, I don't want any other component writing to the log before we write a header into the log indicating that the application is starting up. I know I can introduce ordering by introducing injection dependencies, but this feels like a hack in this case - I would need to add the log header writer as a dependency for every other component which might write to the log, which isn't great at all. Nonetheless it seems like it would be nice to control the order of PicoContainer startup, so is there perhaps some other way? Alternatively I could just keep it simple and stick to my list of Runnable. It does, after all, work.

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• How to Persist URL parameters when CakePHP form validation fails

  - by am2605

  Hi, I'm new to cakephp and trying to write a simple app with it, however I'm stuck with some form validation issues. I have a model named "Person" which hasMany "PersonSkill" objects. To add a "PersonSkill" to a person, I have set it up to call a url like this: http://localhost/myapp/person_skills/add/person_id:3 I have been passing through the person_id because I want to display the name of the person we are adding the skills for. My issue is if the validation fails, the person_id parameter is not persisted to the next request, so the person's name is not displayed. The add method on the controller looks like this: function add() { if (!empty($this->data)) { if ($this->PersonSkill->save($this->data)) { $this->Session->setFlash('Your person has been saved.'); $this->redirect(array('action' => 'view', 'id' => $this->PersonSkill->id)); } } else { $this->Person->id = $this->params['named']['person_id']; $this->set('person', $this->Person->read()); } } In my person_skill add.ctp I set a hidden field which holds the person_id, eg: echo $form->input('person_id', array('type'=>'hidden','value'=>$person['Person']['id'])); Is there a way to persist the person_id url parameter when form validation fails, or is there a better way to do this that I'm missing completely? Any advice would be greatly appreciated.

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• Getting an "i" from GEvent

  - by Cosizzle

  Hello, I'm trying to add an event listener to each icon on the map when it's pressed. I'm storing the information in the database and the value that I'm wanting to retrive is "i" however when I output "i", I get it's last value which is 5 (there are 6 objects being drawn onto the map) Below is the code, what would be the best way to get the value of i, and not the object itself. var drawLotLoc = function(id) { var lotLoc = new GIcon(G_DEFAULT_ICON); // create icon object lotLoc.image = url+"images/markers/lotLocation.gif"; // set the icon image lotLoc.shadow = ""; // no shadow lotLoc.iconSize = new GSize(24, 24); // set the size var markerOptions = { icon: lotLoc }; $.post(opts.postScript, {action: 'drawlotLoc', id: id}, function(data) { var markers = new Array(); // lotLoc[x].description // lotLoc[x].lat // lotLoc[x].lng // lotLoc[x].nighbourhood // lotLoc[x].lot var lotLoc = $.evalJSON(data); for(var i=0; i<lotLoc.length; i++) { var spLat = parseFloat(lotLoc[i].lat); var spLng = parseFloat(lotLoc[i].lng); var latlng = new GLatLng(spLat, spLng) markers[i] = new GMarker(latlng, markerOptions); myMap.addOverlay(markers[i]); GEvent.addListener(markers[i], "click", function() { console.log(i); // returning 5 in all cases. // I _need_ this to be unique to the object being clicked. console.log(this); }); } });

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• What's the order of execution when using IDataErrorInfo?

  - by Benny Jobigan

  Many times with WPF, we use INotifyPropertyChanged and IDataErrorInfo to enable binding and validation on our data objects. I've got a lot of properties that look like this: public SomeObject SomeData { get { return _SomeData; } set { _SomeData = value; OnPropertyChanged("SomeData"); } } Of course, I have an appropriate overridden IDataErrorInfo.this[] in my class to do validation. Question 1) In a binding situation, what happens? For example: User enters new data. Binding writes data to property. Property set method is executed. Binding checks this[] for validation. If the data is invalid, the binding sets the property back to the old value. Property set method is executed again. This is important if you are adding "hooks" into the set method, like: public string PathToFile { get { return _PathToFile; } set { if (_PathToFile != value && // prevent unnecessary actions OnPathToFileChanging(value)) // allow subclasses to do something or stop the setter { _PathToFile = value; OnPathToFileChanged(); // allow subclasses to do something afterwards OnPropertyChanged("PathToFile"); } } }

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• CStdioFile Undeclared Identifier

  - by Eric Regnier

  I am unable to compile my code when using a CStdioFile type. I have included the afx.h header file but I am still receiving errors. What I am trying to do is write a cstring that contains an entire xml document to file. This cstring contains comments inside of it, but when I use other objects such as wofstream to write it to file, these comments are striped out for some reason. So that is why I am trying to write this to file using CStdioFile now. If anyone can help me out as to why I cannot compile my code using CStdioFile, or any other way to write a cstring that contains xml comments to file, please let me know! Below is my code using CStdioFile: CStdioFile xmlFile; xmlFile.Open( "c:\\test.txt", CFile::modeCreate | CFile::modeWrite | CFile::typeText ); xmlFile.WriteString( m_sData ); xmlFile.Close(); And my errors: error C2065: 'CStdioFile' : undeclared identifier error C2065: 'modeCreate' : undeclared identifier error C2065: 'modeWrite' : undeclared identifier error C2065: 'typeText' : undeclared identifier error C2065: 'xmlFile' : undeclared identifier error C2146: syntax error : missing ';' before identifier 'xmlFile' error C2228: left of '.Close' must have class/struct/union type type is ''unknown-type'' error C2228: left of '.Open' must have class/struct/union type type is ''unknown-type'' error C2228: left of '.WriteString' must have class/struct/union type type is ''unknown-type'' error C2653: 'CFile' : is not a class or namespace name error C2653: 'CFile' : is not a class or namespace name error C2653: 'CFile' : is not a class or namespace name error C3861: 'xmlFile': identifier not found, even with argument-dependent lookup error C3861: 'xmlFile': identifier not found, even with argument-dependent lookup error C3861: 'xmlFile': identifier not found, even with argument-dependent lookup

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• Altering lazy-loaded object's private variables

  - by Kevin Pang

  I'm running into an issue with private setters when using NHibernate and lazy-loading. Let's say I have a class that looks like this: public class User { public int Foo {get; private set;} public IList<User> Friends {get; set;} public void SetFirstFriendsFoo() { // This line works in a unit test but does nothing during a live run with // a lazy-loaded Friends list Users(0).Foo = 1; } } The SetFirstFriendsFoo call works perfectly inside a unit test (as it should since objects of the same type can access each others private properties). However, when running live with a lazy-loaded Friends list, the SetFirstFriendsFoo call silently fails. I'm guessing the reason for this is because at run-time, the Users(0).Foo object is no longer of type User, but of a proxy class that inherits from User since the Friends list was lazy-loaded. My question is this: shouldn't this generate a run-time exception? You get compile-time exceptions if you try to access another class's private properties, but when you run into a situation like this is looks like the app just ignores you and continues along its way.

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• APS.NET MVC Ajax: Passing a IList from the View to the Controller

  - by Bpimenta

  I need to pass the grid rows from the view to the controller using POST. The idea is to pass an IList of objects (people) that have the following structure: String Name String Address String ID I want to read the data from the JQGrid and pass it to the controller to fill the IList. I'm trying to build the data object to pass through the Ajax data parameter. Here is the Javascript code: $("#saveButton").click( function() { var returnData = '{'; var existingIDs = $('#listPeople').getDataIDs(); if (idsPeople.length > 0) { for (i=0;i<idsPeople.length;i++) { //Trying to build the obejct data ret = ret + '"people['+ i +'].Name":' $('#listPeople').getRowData(idsPeople[i]).Name + ','; ret = ret + '"people['+ i +'].Address":' $('#listPeople').getRowData(idsPeople[i]).Address+ ','; ret = ret + '"people['+ i +'].Id":' $('#listPeople').getRowData(idsPeople[i]).Id+ ','; //If it has more than one element if (idsPeople.length>1 && (i+1)<idsPeople.length) { ret = ret + ','; } } } ret = ret + '}'; My Ajax function for sending: var url_all = '<%=Url.Action("SaveData") %>; $.ajax({ type: "POST", url: url_all, data: ret, dataType: "json", success: function(){ alert("OK"); }, error: function(){ alert("Error: check SaveData"); } }); My controller: public ActionResult SaveData(IList<PeopleHeader> people){ // using debug to know if "people" variable has any values return Json(true); } The problem I'm getting is an error: "System.NotSupportedException: Fixed size collection", and no data is being delivered. I think my problem relies on creating the object... is there any simpler way of doing this procedure? Thanks in advance,

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• Valueurl Binding On Large Arrays Causes Sluggish User Interface

  - by Hooligancat

  I have a large data set (some 3500 objects) that returns from a remote server via HTTP. Currently the data is being presented in an NSCollectionView. One aspect of the data is a path pack to the server for a small image that represents the data (think thumbnail for simplicity). Bindings works fantastically for the data that is already returned, and binding the image via a valueurl binding is easy to do. However, the user interface is very sluggish when scrolling through the data set - which makes me think that the NSCollectionView is retrieving all the image data instead of just the image data used to display the currently viewable images. I was under the impression that Cocoa controls were smart enough to only retrieve data for the information that is actually being output to the user interface through lazy loading. This certainly seems to be the case with NSTableView - but I could be misguided on this thought. Should valueurl binding act lazily and, moreover, should it act lazily in an NSCollectionView? I could create a caching mechanism (in fact I already have such a thing in place for another application - see my post here if you are interested http://stackoverflow.com/questions/1740209/populating-nsimage-with-data-from-an-asynchronous-nsurlconnection) but I really don't want to go this route if I don't have to for this specific implementation as the user could potentially change data sets often and may only want small sub-sets of the data. Any suggested approaches? Thanks!

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• Reading and writing XML over an SslStream

  - by Mark

  I want to read and write XML data over an SslStream. The data (written and read) consists of objects serialized by an XmlSerializer. I have tried the following; (left some details out for clarity!) TcpClient tcpClient = new TcpClient(server, port); SslStream sslStream = new SslStream(tcpClient.GetStream(), true, new RemoteCertificateValidationCallback(ValidateServerCertificate), null); sslStream.AuthenticateAsClient(server); XmlReader xmlReader = XmlReader.Create(sslStream,readerSettings); XmlWriter xmlWriter = XmlWriter.Create(sslStream,writerSettings); myClass c = new myClass (); XmlSerializer serializer = new XmlSerializer(typeof(myClass)); serializer.Serialize(xmlWriter, c); myClass c2 = (myClass )serializer.Deserialize(xmlReader); First of all, it appears that writing to the stream succeeds. But the XmlSerializer throws an error because of invalid XML. It appears that the first character read from the stream is '00' or a null-character. (I have googled this problem, and see a million people with the same 'problem', but no viable solution.) I can work around this 'issue' by using a StreamReader, read everything into a string and then use that string as input for another stream that the serializer can use. (Very dirty, but it works.) Second problem is, that when I try to use the same SslStream to write a second request, I do not get a response from the Reader. (The server DOES send a valid XML response though!) So the serializer.Serialize(xmlWriter, c3) works, but reading from the stream yields no results. I have tried several different classes that implement Stream. (StreamReader, XmlTextReader, etc.) Anyone has an idea how reading and writing XML data to and from an SslStream is supposed to work? Thanks in advance!

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• syntax help required on templated static member function

  - by omatai

  I have a bunch of containers of object pointers that I want to iterate through in different contexts to produce diagnostics for them. I'm struggling with the syntax required to define the functions... which, on account of these objects filtering through diverse parts of my application, seem best encapsulated in a dedicated diagnostics class thus: // Code sketch only - detail fleshed out below... class ObjectListDiagnoser { public: static void GenerateDiagnostics( /* help required here! */ ); }; ... // Elsewhere in the system... ObjectListDiagnoser::GenerateDiagnostics( /* help required here! */ ); What I'd like to be able to do (in places across my application) is at least this: std::vector<MyObject *> objGroup1; std::list<MyObject *> objGroup2; ObjectListDiagnoser::GenerateDiagnostics( objGroup1.begin(), objGroup1.end() ); ObjectListDiagnoser::GenerateDiagnostics( objGroup2.begin(), objGroup2.end() ); ObjectListDiagnoser::GenerateDiagnostics( objGroup1.rbegin(), objGroup1.rend() ); I have tried to template my function in two ways, with no success: class ObjectListDiagnoser { public: // 1 - nope. template <class ObjIter> static void GenerateDiagnostics( ObjIter first, ObjIter last ); // 2. - nope. template <class Container, class ObjIter> static void GenerateDiagnostics( Container<MyObject *>::ObjIter first, Container<MyObject *>::ObjIter last ); }; Can someone provide the correct syntax for this? The container type will vary, and the direction of iteration will vary, but always for the same type of object.

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• Django: Serving Media Behind Custom URL

  - by TheLizardKing

  So I of course know that serving static files through Django will send you straight to hell but I am confused on how to use a custom url to mask the true location of the file using Django. http://stackoverflow.com/questions/2681338/django-serving-a-download-in-a-generic-view but the answer I accepted seems to be the "wrong" way of doing things. urls.py: url(r'^song/(?P<song_id>\d+)/download/$', song_download, name='song_download'), views.py: def song_download(request, song_id): song = Song.objects.get(id=song_id) fsock = open(os.path.join(song.path, song.filename)) response = HttpResponse(fsock, mimetype='audio/mpeg') response['Content-Disposition'] = "attachment; filename=%s - %s.mp3" % (song.artist, song.title) return response This solution works perfectly but not perfectly enough it turns out. How can I avoid having a direct link to the mp3 while still serving through nginx/apache? EDIT 1 - ADDITIONAL INFO Currently I can get my files by using an address such as: http://www.example.com/music/song/1692/download/ But the above mentioned method is the devil's work. How can I accomplished what I get above while still making nginx/apache serve the media? Is this something that should be done at the webserver level? Some crazy mod_rewrite? http://static.example.com/music/Aphex%20Twin%20-%20Richard%20D.%20James%20(V0)/10%20Logon-Rock%20Witch.mp3

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• How to develop JSP/Servlets Web App using MVC pattern?

  - by A.S al-shammari

  I'm developing a JSP/Servlets web app (no frameworks). I want to use MVC pattern. I designed my project like this : Controller :a servlet that reads a request, extracts the values,communicates with model objects and gives information to a JSP page. View : JSP Pages. Model : Java Classes / Java Beans .. etc . The problem : Index.jsp is the starting point (default page) in my web site. So, the Index.jsp becomes the controller to parse the request! .For example , the following request : index.jsp?section=article&id=10 parsed in index.jsp as following : <div class="midcol"> <!-- Which section? --> <%String fileName = request.getParameter("section"); if (fileName == null) { fileName = "WEB-INF/jspf/frontpage.jsp"; } else { fileName = "WEB-INF/jspf/" + fileName + ".jsp"; } %> <jsp:include page='<%= fileName%>' /> </div> Here, I can't force the servlet to be a controller .. because the index.jsp is the controller here since it's the starting point! Is there any solution to forward the request from index.jsp to the servlet and then go back to index.jsp ? Or any solution that achieves the MVC goal - the servlet should be the controller - ? I'm thinking of making a FrontPageController servlet as default page instead of index.jsp ! but I don't know if it's a perfect idea ?!

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• A view "transparent" to touches in some areas

  - by Mike

  I have this transparent view that covers the whole screen. I using this view to group objects because I need to run them together around a specific anchor point. Lets call this view transparentView. At some point, transparentView contains two subviews. Two vertical bars full of icons, one on the left and one on the right of the screen. I need these bars and their icons to respond to touches, so I have to set transparentView setUserInteraction to YES. The area between the two vertical bars are totally transparent. transparentView is on top of other views and I need these other views to respond to taps but, the transparent area of transparentView are intercepting the taps and not letting them go thru to the view below. This transparent view is a UIImageView based class. I have tried to forward taps on that class, using - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { [self.nextResponder touchesBegan: touches withEvent:event]; } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [self.nextResponder touchesMoved: touches withEvent:event]; } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { [self.nextResponder touchesEnded: touches withEvent:event]; } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { [self touchesEnded:touches withEvent:event]; } but this is not working. How can I do that? thanks.

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• SubSonic 3 screws up selecteditem?

  - by SteveCav

  If you have a moment, please try this: -Download Subsonic 3. -Start a new proj and add SS's ActiveRecord templates. -Point it to any SQL Server DB and generate the classes. -Add a WPF project. -Create a window and add a combobox or listbox. -Set the ItemsSource from the SS DAL, and format it how you wish. -Add a button that will show you some value from the SelectedItem (using messagebox, console, whatever). -Run the project. -Click on the third item in the list. -Click on the second item in the list. -Click on the button. When I do that, the button gives me the value of the THIRD item, not the second. In other words, once the SelectedItem is set the first time it STAYS, no matter which item is subsequently highlighted on the screen. This is happening to me whatever control I use (combobox, listbox, even datagrid) and it ONLY happens with Subsonic Activerecord objects. If I write my own POCOs with identical properties and bind a list of them instead, the controls behave as expected. Does this happen to you? Any ideas?

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• Caching sitemaps in django

  - by michuk

  I implemented a simple sitemap class using django's default sitemap app. As it was taking a long time to execute, I added manual caching: class ShortReviewsSitemap(Sitemap): changefreq = "hourly" priority = 0.7 def items(self): # try to retrieve from cache result = get_cache(CACHE_SITEMAP_SHORT_REVIEWS, "sitemap_short_reviews") if result!=None: return result result = ShortReview.objects.all().order_by("-created_at") # store in cache set_cache(CACHE_SITEMAP_SHORT_REVIEWS, "sitemap_short_reviews", result) return result def lastmod(self, obj): return obj.updated_at The problem is that memcache allows only max 1MB object. This one was bigger that 1MB, so storing into cache failed: >7 SERVER_ERROR object too large for cache The problem is that django has an automated way of deciding when it should divide the sitemap file into smalled ones. According to the docs (http://docs.djangoproject.com/en/dev/ref/contrib/sitemaps/): You should create an index file if one of your sitemaps has more than 50,000 URLs. In this case, Django will automatically paginate the sitemap, and the index will reflect that. What do you think would be the best way to enable caching sitemaps? - Hacking into django sitemaps framework to restrict a single sitemap size to, let's say, 10,000 records seems like the best idea. Why was 50,000 chosen in the first place? Google advice? random number? - Or maybe there is a way to allow memcached store bigger files? - Or perhaps onces saved, the sitemaps should be made available as static files? This would mean that instead of caching with memcached I'd have to manually store the results in the filesystem and retrieve them from there next time when the sitemap is requested (perhaps cleaning the directory daily in a cron job). All those seem very low level and I'm wondering if an obvious solution exists...

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• Datagridview Winforms Add or Delete Rows in Edit Mode with Collection Binding

  - by user630548

  In my datagridview, I bind a List of objects named 'ProductLine'. But unfortunately with this approach I cannot 'Add' or 'Delete' rows to the datagridview in edit mode. When I create a fresh new order I can Add or Delete rows but once I save it and try to open it in Edit then it doesn't let me 'Add' or 'Delete' (via keyboard). Any idea? Here is the code for this: If it is a fresh Order then I do something like this: private void Save(){ for (int i = 0; i <= dtgProdSer.RowCount - 1; i++) { if ((itemList != null) && (itemList.Count > i)) productLine = itemList[i]; else productLine = new ProductLine(); productLine.Amount = Convert.ToDouble(dataGridViewTextBoxCell.Value); } } And if it is an Edit then in the Form_Load I check ProductId is NON Zero then I do the following: private void fillScreen{ dtgProdSer.DataSource = itemList; } But with this I cannot Add or Delete Rows in Edit mode. Any advise is greatly appreciated.

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• Django Threaded Commenting System

  - by Yasin Ozel

  (and sorry for my english) I am learning Python and Django. Now, my challange is developing threaded generic comment system. There is two models, Post and Comment. -Post can be commented. -Comment can be commented. (endless/threaded) -Should not be a n+1 query problem in system. (No matter how many comments, should not increase the number of queries) My current models are like this: class Post(models.Model): title = models.CharField(max_length=100) content = models.TextField() child = generic.GenericRelation( 'Comment', content_type_field='parent_content_type', object_id_field='parent_object_id' ) class Comment(models.Model): content = models.TextField() child = generic.GenericRelation( 'self', content_type_field='parent_content_type', object_id_field='parent_object_id' ) parent_content_type = models.ForeignKey(ContentType) parent_object_id = models.PositiveIntegerField() parent = generic.GenericForeignKey( "parent_content_type", "parent_object_id") Are my models right? And how can i get all comment (with hierarchy) of post, without n+1 query problem? Note: I know mttp and other modules but I want to learn this system. Edit: I run "Post.objects.all().prefetch_related("child").get(pk=1)" command and this gave me post and its child comment. But when I wanna get child command of child command a new query is running. I can change command to ...prefetch_related("child__child__child...")... then still a new query running for every depth of child-parent relationship. Is there anyone who has idea about resolve this problem?

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• MVVM pattern: ViewModel updates after Model server roundtrip

  - by Pavel Savara

  I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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• Considerations when architecting an application using Dependency Injection

  - by Dan Bryant

  I've begun experimenting with dependency injection (in particular, MEF) for one of my projects, which has a number of different extensibility points. I'm starting to get a feel for what I can do with MEF, but I'd like to hear from others who have more experience with the technology. A few specific cases: My main use case at the moment is exposing various singleton-like services that my extensions make use of. My Framework assembly exposes service interfaces and my Engine assembly contains concrete implementations. This works well, but I may not want to allow all of my extensions to have access to all of my services. Is there a good way within MEF to limit which particular imports I allow a newly instantiated extension to resolve? This particular application has extension objects that I repeatedly instantiate. I can import multiple types of Controllers and Machines, which are instantiated in different combinations for a Project. I couldn't find a good way to do this with MEF, so I'm doing my own type discovery and instantiation. Is there a good way to do this within MEF or other DI frameworks? I welcome input on any other things to watch out for or surprising capabilities you've discovered that have changed the way you architect.

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• Email Collector / Implementation

  - by Tian

  I am implementing a simple RoR webpage that collect emails from visitors and store them as objects. I'm using it as a mini-project to try RoR and BDD. I can think of 3 features for Cucumber: 1. User submits a valid email address 2. User submits an existing email address 3. User submits an invalid email My question is, for scenarios 2 and 3, is it better to handle this via the controller? or as methods in a class? Perhaps something that throws errors if an instance is instantiated in sceanrio 2 or 3? Implementation is below, love to hear some code reviews in addition to answers to questions above. Thanks! MODEL: class Contact < ActiveRecord::Base attr_accessor :email end VIEW: <h1>Welcome To My Experiment</h1> <p>Find me in app/views/welcome/index.html.erb</p> <%= flash[:notice] %> <% form_for @contact, :url => {:action => "index"} do |f| %> <%= f.label :email %><br /> <%= f.text_field :email %> <%= submit_tag 'Submit' %> <% end %> CONTROLLER: class WelcomeController < ApplicationController def index @contact = Contact.new unless params[:contact].nil? @contact = Contact.create!(params[:contact]) flash[:notice] = "Thank you for your interest, please check your mailbox for confirmation" end end end

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• findViewById returns null in new Intent

  - by drozzy

  I am having a problem where in the started Intent, the findViewById returns null. Is there anything special I should know about starting a new intent? It goes something like this for me: //in the MainList class Intent stuffList = new Intent(this, StuffList.class); then in the new Stuff's constructor: public class StuffList extends ListActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.setContentView(R.layout.stuff_list); ... this.setListAdapter(new StuffAdapter(this, my_cursor)); and in the StuffAdapter I do my usual view and data retrieval. Note the line where findViewById returns null: class ViewWrapper{ View base; TextView label = null; ViewWrapper(View base){ this.base = base; } TextView getLabel(){ if(label == null){ label = (TextView)base.findViewById(R.id.my_label); // returns NULL } return label;} } class StuffAdapter extends CursorAdapter{ StuffAdapter(Context context, Cursor cursor){ super(context, cursor); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { LayoutInflater inflater = getLayoutInflater(); View row = inflater.inflate(R.layout.stuff_list, parent, false); ViewWrapper wrapper = new ViewWrapper(row); row.setTag(wrapper); return(row); } @Override public void bindView(View row, Context context, Cursor cursor) { ViewWrapper wrapper = (ViewWrapper)row.getTag(); TextView label = wrapper.getLabel(); // also NULL //this throws exception of course label.setText(cursor.getString("title")); } } The curious thing is that in the class that calls intent (MainList class), I do Exactly the same thing (i list a bunch of objects), and it Works! however when I try to do it in an Intent - it can't seem to find the view by id.

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• Serializing a part of object graph

  - by Felix

  Hi all, I have a problem regarding Java custom serialization. I have a graph of objects and want to configure where to stop when I serialize a root object from client to server. Let's make it a bit concrete, clear by giving a sample scenario. I have Classes of type Company Employee (abstract) Manager extends Employee Secretary extends Employee Analyst extends Employee Project Here are the relations: Company(1)---(n)Employee Manager(1)---(n)Project Analyst(1)---(n)Project Imagine, I'm on the client side and I want to create a new company, assign it 10 employees (new or some existing) and send this new company to the server. What I expect in this scenario is to serialize the company and all bounding employees to the server side, because I'll save the relations on the database. So far no problem, since the default Java serialization mechanism serializes the whole object graph, excluding the field which are static or transient. My goal is about the following scenario. Imagine, I loaded a company and its 1000 employees from the server to the client side. Now I only want to rename the company's name (or some other field, that directly belongs to the company) and update this record. This time, I want to send only the company object to the server side and not the whole list of employees (I just update the name, the employees are in this use case irrelevant). My aim also includes the configurability of saying, transfer the company AND the employees but not the Project-Relations, you must stop there. Do you know any possibility of achieving this in a generic way, without implementing the writeObject, readObject for every single Entity-Object? What would be your suggestions? I would really appreciate your answers. I'm open to any ideas and am ready to answer your questions in case something is not clear.

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• JS sort works in Firefox but not IE - can't work out why

  - by Max Williams

  I have a line in a javascript function that sort an array of objects based on the order of another array of strings. This is working in firefox but not in IE and i don't know why. Here's what my data looks like going into the sort call. (I'm using an array of three items just to illustrate the point here). //cherry first then the rest in alphabetical order originalData = ['cherry','apple','banana','clementine','nectarine','plum'] //data before sorting - note how clementine is second item - we wan to to to be after apple and banana csub = [ {"value":"cherry","data":["cherry"],"result":"cherry"}, {"value":"clementine","data":["clementine"],"result":"clementine"}, {"value":"apple","data":["apple"],"result":"apple"}, {"value":"banana","data":["banana"],"result":"banana"}, {"value":"nectarine","data":["nectarine"],"result":"nectarine"}, {"value":"plum","data":["plum"],"result":"plum"} ] //after sorting, csub has been rearranged but still isn't right: clementine is before banana csubSorted = [ {"value":"cherry","data":["cherry"],"result":"cherry"}, {"value":"apple","data":["apple"],"result":"apple"}, {"value":"clementine","data":["clementine"],"result":"clementine"}, {"value":"banana","data":["banana"],"result":"banana"}, {"value":"nectarine","data":["nectarine"],"result":"nectarine"}, {"value":"plum","data":["plum"],"result":"plum"} ] Here's the actual sort code: csubSorted = csub.sort(function(a,b){ return (originalData.indexOf(a.value) > originalData.indexOf(b.value)); }); Can anyone see why this wouldn't work? Is the basic javascript sort function not cross-browser compatible? Can i do this a different way (eg with jquery) that would be cross-browser? grateful for any advice - max

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