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  • Django: order by count of a ForeignKey field?

    - by AP257
    This is almost certainly a duplicate question, in which case apologies, but I've been searching for around half an hour on SO and can't find the answer here. I'm probably using the wrong search terms, sorry. I have a User model and a Submission model. Each Submission has a ForeignKey field called user_submitted for the User who uploaded it. class Submission(models.Model): uploaded_by = models.ForeignKey('User') class User(models.Model): name = models.CharField(max_length=250 ) My question is pretty simple: how can I get a list of the three users with the most Submissions? I trued creating a num_submissions method on the User model: def num_submissions(self): num_submissions = Submission.objects.filter(uploaded_by=self).count() return num_submissions and then doing: top_users = User.objects.filter(problem_user=False).order_by('num_submissions')[:3] but this fails, as do all the other things I've tried. Can I actually do it using a smart database query? Or should I just do something more hacky in the views file?

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  • Sort/Enumerate an NSArray from somewhere in the middle?

    - by Kenny Winker
    I have an NSArray, with objects ordered like so: a b c d e f I would like to enumerate through this array in this order: c d e f a b i.e. starting at some point that is not the beginning, but hitting all the items. I imagine this is a matter of sorting first and then enumerating the array, but I'm not sure if that's the best technique... or, frankly, how to sort the array like this. Edit Adding details: These will be relatively small arrays, varying from 3 to 10 objects. No concurrent access. I'd like to permanently alter the sort order of the array each time I do this operation.

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  • Reflection in unit tests for checking code coverage

    - by Gary
    Here's the scenario. I have VO (Value Objects) or DTO objects that are just containers for data. When I take those and split them apart for saving into a DB that (for lots of reasons) doesn't map to the VO's elegantly, I want to test to see if each field is successfully being created in the database and successfully read back in to rebuild the VO. Is there a way I can test that my tests cover every field in the VO? I had an idea about using reflection to iterate through the fields of the VO's as part of the solution, but maybe you guys have solved the problem before? I want this test to fail when I add fields in the VO, and don't remember to add checks for it in my tests.

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  • How to populate GridView if Internet not available but images already cached to SD Card

    - by Sophie
    Hello I am writing an Application in which i am parsing JSON Images and then caching into SD Card. What I want to do ? I want to load images into GridView from JSON (by caching images into SD Card), and wanna populate GridView (no matter Internet available or not) once images already downloaded into SD Card. What I am getting ? I am able to cache images into SD Card, also to populate GridView, but not able to show images into GridView (if Internet not available) but images cached into SD Card @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { myGridView = inflater.inflate(R.layout.fragment_church_grid, container, false); if (isNetworkAvailable()) { new DownloadJSON().execute(); } else { Toast.makeText(getActivity(), "Internet not available !", Toast.LENGTH_LONG).show(); } return myGridView ; } private boolean isNetworkAvailable() { ConnectivityManager cm = (ConnectivityManager) getActivity().getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo info = cm.getActiveNetworkInfo(); return (info != null); } // DownloadJSON AsyncTask private class DownloadJSON extends AsyncTask<Void, Void, Void> { @Override protected void onPreExecute() { super.onPreExecute(); // Create a progressdialog mProgressDialog = new ProgressDialog(getActivity()); // Set progressdialog title mProgressDialog.setTitle("Church Application"); // Set progressdialog message mProgressDialog.setMessage("Loading Images..."); mProgressDialog.setIndeterminate(false); // Show progressdialog mProgressDialog.show(); } @Override protected Void doInBackground(Void... params) { // Create an array arraylist = new ArrayList<HashMap<String, String>>(); // Retrieve JSON Objects from the given URL address jsonobject = JSONfunctions .getJSONfromURL("http://snapoodle.com/APIS/android/feed.php"); try { // Locate the array name in JSON jsonarray = jsonobject.getJSONArray("print"); for (int i = 0; i < jsonarray.length(); i++) { HashMap<String, String> map = new HashMap<String, String>(); jsonobject = jsonarray.getJSONObject(i); // Retrive JSON Objects map.put("saved_location", jsonobject.getString("saved_location")); // Set the JSON Objects into the array arraylist.add(map); } } catch (JSONException e) { Log.e("Error", e.getMessage()); e.printStackTrace(); } return null; } @Override protected void onPostExecute(Void args) { // Locate the listview in listview_main.xml listview = (GridView) shriRamView.findViewById(R.id.listview); // Pass the results into ListViewAdapter.java adapter = new ChurchImagesAdapter(getActivity(), arraylist); // Set the adapter to the ListView listview.setAdapter(adapter); // Close the progressdialog mProgressDialog.dismiss(); } } }

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  • Python 3.0 - Dynamic Class Instance Naming

    - by Jon
    I want to use a while loop to initialize class objects with a simple incremented naming convention. The goal is to be able to scale the number of class objects at will and have the program generate the names automatically. (ex. h1...h100...h1000...) Each h1,h2,h3... being its own instance. Here is my first attempt... have been unable to find a good example. class Korker(object): def __init__(self,ident,roo): self.ident = ident self.roo = roo b = 1 hwinit = 'h' hwstart = 0 while b <= 10: showit = 'h' + str(b) print(showit) #showit seems to generate just fine as demonstrated by print str(showit) == Korker("test",2) #this is the line that fails b += 1 The errors I get range from a string error to a cannot use function type error.... Any help would be greatly appreciated.

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  • What classes should I map against with NHibernate?

    - by apollodude217
    Currently, we use NHibernate to map business objects to database tables. Said business objects enforce business rules: The set accessors will throw an exception on the spot if the contract for that property is violated. Also, the properties enforce relationships with other objects (sometimes bidirectional!). Well, whenever NHibernate loads an object from the database (e.g. when ISession.Get(id) is called), the set accessors of the mapped properties are used to put the data into the object. What's good is that the middle tier of the application enforces business logic. What's bad is that the database does not. Sometimes crap finds its way into the database. If crap is loaded into the application, it bails (throws an exception). Sometimes it clearly should bail because it cannot do anything, but what if it can continue working? E.g., an admin tool that gathers real-time reports runs a high risk of failing unnecessarily instead of allowing an admin to even fix a (potential) problem. I don't have an example on me right now, but in some instances, letting NHibernate use the "front door" properties that also enforce relationships (especially bidi) leads to bugs. What are the best solutions? Currently, I will, on a per-property basis, create a "back door" just for NHibernate: public virtual int Blah {get {return _Blah;} set {/*enforces BR's*/}} protected virtual int _Blah {get {return blah;} set {blah = value;}} private int blah; I showed the above in C# 2 (no default properties) to demonstrate how this gets us basically 3 layers of, or views, to blah!!! While this certainly works, it does not seem ideal as it requires the BL to provide one (public) interface for the app-at-large, and another (protected) interface for the data access layer. There is an additional problem: To my knowledge, NHibernate does not give you a way to distinguish between the name of the property in the BL and the name of the property in the entity model (i.e. the name you use when you query, e.g. via HQL--whenever you give NHibernate the name (string) of a property). This becomes a problem when, at first, the BR's for some property Blah are no problem, so you refer to it in your O/R mapping... but then later, you have to add some BR's that do become a problem, so then you have to change your O/R mapping to use a new _Blah property, which breaks all existing queries using "Blah" (common problem with programming against strings). Has anyone solved these problems?!

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  • XML serialization options in .NET

    - by Borek
    I'm building a service that returns an XML (no SOAP, no ATOM, just plain old XML). Say that I have my domain objects already filled with data and just need to transform them to the XML format. What options do I have on .NET? Requirements: The transformation is not 1:1. Say that I have an Address property of type Address with nested properties like Line1, City, Postcode etc. This may need to result in an XML like <xaddr city="...">Line1, Postcode</xaddr>, i.e. quite different. Some XML elements/attributes are conditional, for example, if a Customer is under 18, the XML needs to contain some additional information. I only need to serialize the objects to XML, the other direction (XML to objects) is not important Some technologies, i.e. Data Contracts use .NET attributes. Other means of configuration (external XML config, buddy classes etc.) would be a plus. Here are the options as I see them as the moment. Corrections / additions will be very welcome. String concatenation - forget it, it was a joke :) Linq 2 XML - complete control but quite a lot of hand written code, would need good suite of unit tests View engines in ASP.NET MVC (or even Web Forms theoretically), the logic being in controllers. It's a question how to structure it, I can have simple rules engine in my controller(s) and one view template per each possible output, or have the decision logic directly in the template. Both have upsides and downsides. XML Serialization - I'm not sure about the flexibility here Data Contracts from WCF - not sure about the flexibility either, plus would they work in a simple ASP.NET MVC app (non-WCF service)? Are they a super-set of the standard XML serialization now? If it exists, some XML-to-object mapper. The more I think about it the more I think I'm looking for something like this but I couldn't find anything appropriate. Any comments / other options?

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  • Same IL code, different output - how is it possible?

    - by Hali
    When I compile this code with mono (gmcs) and run it, it outputs -1 (both with mono and .Net framework). When I compile it with VS (csc), it outputs -1 when I run it with mono, and 0 when I run it with the .Net framework. The code in question is: using System; public class Program { public static void Main() { Console.WriteLine(string.Compare("alo\0alo\0", "alo\0alo\0\0", false, System.Globalization.CultureInfo.InvariantCulture)); } } Compiled with VS: .method public hidebysig static void Main() cil managed { .entrypoint // Code size 29 (0x1d) .maxstack 8 IL_0000: nop IL_0001: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 ) // a.l.o...a.l.o... IL_0006: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 // a.l.o...a.l.o... 00 00 ) IL_000b: ldc.i4.0 IL_000c: call class [mscorlib]System.Globalization.CultureInfo [mscorlib]System.Globalization.CultureInfo::get_InvariantCulture() IL_0011: call int32 [mscorlib]System.String::Compare(string, string, bool, class [mscorlib]System.Globalization.CultureInfo) IL_0016: call void [mscorlib]System.Console::WriteLine(int32) IL_001b: nop IL_001c: ret } // end of method Program::Main Compiled with mono: .method public hidebysig static void Main() cil managed { .entrypoint // Code size 27 (0x1b) .maxstack 8 IL_0000: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 ) // a.l.o...a.l.o... IL_0005: ldstr bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 // a.l.o...a.l.o... 00 00 ) IL_000a: ldc.i4.0 IL_000b: call class [mscorlib]System.Globalization.CultureInfo [mscorlib]System.Globalization.CultureInfo::get_InvariantCulture() IL_0010: call int32 [mscorlib]System.String::Compare(string, string, bool, class [mscorlib]System.Globalization.CultureInfo) IL_0015: call void [mscorlib]System.Console::WriteLine(int32) IL_001a: ret } // end of method Program::Main The only difference is the two extra NOP instructions in the VS version. How is it possible?

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  • C# 3 dimensional array definition issue

    - by George2
    Hello everyone, My following code has compile error, Error 1 Cannot implicitly convert type 'TestArray1.Foo[,,*]' to 'TestArray1.Foo[][][]' C:\Users\lma\Documents\Visual Studio 2008\Projects\TestArray1\TestArray1\Program.cs 17 30 TestArray1 Does anyone have any ideas? Here is my whole code, I am using VSTS 2008 + Vista 64-bit. namespace TestArray1 { class Foo { } class Program { static void Main(string[] args) { Foo[][][] foos = new Foo[1, 1, 1]; return; } } } EDIT: version 2. I have another version of code, but still has compile error. Any ideas? Error 1 Invalid rank specifier: expected ',' or ']' C:\Users\lma\Documents\Visual Studio 2008\Projects\TestArray1\TestArray1\Program.cs 17 41 TestArray1 Error 2 Invalid rank specifier: expected ',' or ']' C:\Users\lma\Documents\Visual Studio 2008\Projects\TestArray1\TestArray1\Program.cs 17 44 TestArray1 namespace TestArray1 { class Foo { } class Program { static void Main(string[] args) { Foo[][][] foos = new Foo[1][1][1]; return; } } } EDIT: version 3. I think I want to have a jagged array. And after learning from the fellow guys. Here is my code fix, and it compile fine in VSTS 2008. What I want is a jagged array, and currently I need to have only one element. Could anyone review whether my code is correct to implement my goal please? namespace TestArray1 { class Foo { } class Program { static void Main(string[] args) { Foo[][][] foos = new Foo[1][][]; foos[0] = new Foo[1][]; foos[0][0] = new Foo[1]; foos[0][0][0] = new Foo(); return; } } } thanks in advance, George

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  • What are some "mental steps" a developer must take to begin moving from SQL to NO-SQL (CouchDB, Fath

    - by Byron Sommardahl
    I have my mind firmly wrapped around relational databases and how to code efficiently against them. Most of my experience is with MySQL and SQL. I like many of the things I'm hearing about document-based databases, especially when someone in a recent podcast mentioned huge performance benefits. So, if I'm going to go down that road, what are some of the mental steps I must take to shift from SQL to NO-SQL? If it makes any difference in your answer, I'm a C# developer primarily (today, anyhow). I'm used to ORM's like EF and Linq to SQL. Before ORMs, I rolled my own objects with generics and datareaders. Maybe that matters, maybe it doesn't. Here are some more specific: How do I need to think about joins? How will I query without a SELECT statement? What happens to my existing stored objects when I add a property in my code? (feel free to add questions of your own here)

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  • Global Import Aliasing in .NET

    - by Josh Stodola
    Using import aliasing in a single class, we can reference class library namespaces by assigning our own custom alias like this: Imports Db = Company.Lib.Data.Objects And then we are able to reference the classes inside of Company.Lib.Data.Objects by using the Db alias that we assigned. Is it possible to do this at the global level so that the alias is applied to the entire solution instead of the given file? Currently, we are working with web applications, so I was hoping we could add something to web.config, but I am also interested in whether or not this is possible with windows forms, console apps, and/or class libraries.

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  • Displaying change of content through parent

    - by Mikhail
    I have DHTML content inside a fieldset. This includes plain html, nested objects (even other fieldsets), and value change of input, select, and textarea objects. I'd like to change the border of the fieldset if the contents have been changed. The following works: $('fieldset[name=qsfs127]').children('input').change(function(){ $(this).parent('fieldset').css({border:'1px solid red'}); }) This handles the input; I can extend it to select and textarea. Questions: How can I do the same for html changes? Can all of this change-tracking be done by comparing current html() to stored one? If yes for (2), will this handle cases of "undo"? Edit: I have a button that ajax-uploads contents, and saves the changes. I then remove the border color

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  • How do I 'globally' catch exceptions thrown in object instances.

    - by SleepyBobos
    I am currently writing a winforms application (C#). I am making use of the Enterprise Library Exception Handling Block, following a fairly standard approach from what I can see. IE : In the Main method of Program.cs I have wired up event handler to Application.ThreadException event etc. This approach works well and handles the applications exceptional circumstances. In one of my business objects I throw various exceptions in the Set accessor of one of the objects properties set { if (value > MaximumTrim) throw new CustomExceptions.InvalidTrimValue("The value of the minimum trim..."); if (!availableSubMasterWidthSatisfiesAllPatterns(value)) throw new CustomExceptions.InvalidTrimValue("Another message..."); _minimumTrim = value; } My logic for this approach (without turning this into a 'when to throw exceptions' discussion) is simply that the business objects are responsible for checking business rule constraints and throwing an exception that can bubble up and be caught as required. It should be noted that in the UI of my application I do explictly check the values that the public property is being set to (and take action there displaying friendly dialog etc) but with throwing the exception I am also covering the situation where my business object may not be used by a UI eg : the Property is being set by another business object for example. Anyway I think you all get the idea. My issue is that these exceptions are not being caught by the handler wired up to Application.ThreadException and I don't understand why. From other reading I have done the Application.ThreadException event and it handler "... catches any exception that occurs on the main GUI thread". Are the exceptions being raised in my business object not in this thread? I have not created any new threads. I can get the approach to work if I update the code as follows, explicity calling the event handler that is wired to Application.ThreadException. This is the approach outlined in Enterprise Library samples. However this approach requires me to wrap any exceptions thrown in a try catch, something I was trying to avoid by using a 'global' handler to start with. try { if (value > MaximumTrim) throw new CustomExceptions.InvalidTrimValue("The value of the minimum..."); if (!availableSubMasterWidthSatisfiesAllPatterns(value)) throw new CustomExceptions.InvalidTrimValue("Another message"); _minimumTrim = value; } catch (Exception ex) { Program.ThreadExceptionHandler.ProcessUnhandledException(ex); } I have also investigated using wiring a handler up to AppDomain.UnhandledException event but this does not catch the exceptions either. I would be good if someone could explain to me why my exceptions are not being caught by my global exception handler in the first code sample. Is there another approach I am missing or am I stuck with wrapping code in try catch, shown above, as required?

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  • How to use Zend_Cache Identifier ?

    - by ArneRie
    Hi Folks, i think iam getting crazy, iam trying to implement Zend_Cache to cache my database query. I know how it works and how to configure. But i cant find a good way to set the Identifier for the cache entrys. I have an method wich search for records in my database (based on an array with search values). /** * Find Record(s) * Returns one record, or array with objects * * @param array $search Search columns => value * @param integer $limit Limit results * @return array One record , or array with objects */ public function find(array $search, $limit = null) { $identifier = 'NoIdea'; if (!($data = $this->_cache->load($identifier))) { // fetch // save to cache with $identifier.. } But what kind of identifier can use in this situation?

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  • How can I ignore properties of a component using Fluent Nhibernate's AutoPersistenceModel?

    - by Jason
    I am using Fluent NHibernate AutoMappings to map my entities, including a few component objects. One of the component objects includes a property like the following: public string Value { set _value = value; } This causes an NHibernate.PropertyNotFoundException: "Could not find a getter for property 'Value'..." I want to ignore this property. I tried creating an IAutoMappingOverride for the component class but I couldn't use AutoMapping<.IgnoreProperty(x = x.Value) for the same reason. "The property or indexer 'MyComponent.Value' cannot be used in this context because it lacks the get accessor" I've also looked at IComponentConvention but can't see anyway of altering the mappings with this convention. Any help would be appreciated... Thanks

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  • AS3: Removing EventListeners without knowing amount or names

    - by DevEight
    Hello! First shortly about how my site works: When a link is clicked it checks if something is already displayed in either the Left or Right side of the screen (the website looks like a book, so I have a left page I want to display information on and a right page). If there is already something showing it hides it and displays the new object, together with this it enables all the buttons within that object (I have separate functions to set up each object). An example of such an EventListener would be: pathTo.Button1.addEventListener(MouseEvent.CLICK, function():void {showText(side, object)}); What I'm trying to do is to remove all the previous set EventListeners without having to create separate functions for removing the links inside every object as well. Shorter version: How do I remove all EventListeners on all objects inside another object? The only variable I want to store is the object containing everything. There are however not always EventListeners within the objects.

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  • Protecting critical sections based on a condition in C#

    - by NAADEV
    Hello, I'm dealing with a courious scenario. I'm using EntityFramework to save (insert/update) into a SQL database in a multithreaded environment. The problem is i need to access database to see whether a register with a particular key has been already created in order to set a field value (executing) or it's new to set a different value (pending). Those registers are identified by a unique guid. I've solved this problem by setting a lock since i do know entity will not be present in any other process, in other words, i will not have same guid in different processes and it seems to be working fine. It looks something like that: static readonly object LockableObject = new object(); static void SaveElement(Entity e) { lock(LockableObject) { Entity e2 = Repository.FindByKey(e); if (e2 != null) { Repository.Insert(e2); } else { Repository.Update(e2); } } } But this implies when i have a huge ammount of requests to be saved, they will be queued. I wonder if there is something like that (please, take it just as an idea): static void SaveElement(Entity e) { (using ThisWouldBeAClassToProtectBasedOnACondition protector = new ThisWouldBeAClassToProtectBasedOnACondition(e => e.UniqueId) { Entity e2 = Repository.FindByKey(e); if (e2 != null) { Repository.Insert(e2); } else { Repository.Update(e2); } } } The idea would be having a kind of protection that protected based on a condition so each entity e would have its own lock based on e.UniqueId property. Any idea?

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  • Is it possible to Kick off a java process under Windows Service with C#?

    - by Wing C. Chen
    I would like to wrap a java program into a windows service with C# using System.ServiceProcess.ServiceBase. So I came up with the following code: /// <summary> /// The main entry point for the application. /// </summary> static void Main() { System.ServiceProcess.ServiceBase.Run(new JavaLauncher()); } protected override void OnStart(string[] args) { Thread _thread; _thread = new Thread(StartService); _thread.Start(); base.OnStart(args); } protected override void OnStop() { Thread _thread; _thread = new Thread(StopService); _thread.Start(); base.OnStop(); } static public void StartService() { System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.EnableRaisingEvents = false; proc.StartInfo.FileName = "javaw"; proc.StartInfo.Arguments = config.generateLaunchCommand(); proc.Start(); } static public void StopService() { System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.EnableRaisingEvents = false; proc.StartInfo.FileName = "javaw"; proc.StartInfo.Arguments = "-jar stop.jar"; proc.Start(); } Firstly I had to use Threads in OnStart and OnStop. If not, an exception occurs complaining that the service is terminated because of doing nothing. Secondly, the service can be hooked up to windows smoothly. However, the service terminates a short while after it is started. I looked into the process monitor, only the service process stays alive for that short while, the javaw process never showed up, however. Is there anyone who knows how this can be fixed? It works fine in an ordinary console environment. I think it has something to do with Windows service.

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  • Program freezing when syncing a ldap database (100+ entries added)

    - by djerry
    Hey guys, I'm updating a ldap database. I need to add a list of users to the db. I've written a simple foreach loop. There are about 180 users i need to add, but at the 128th user, the program freezes. I know ldap is really used for querying (fast), and that adding and modifying entries will not go as smooth as a search query, but is it normal that the program freezes while doing this? I'll post some code just in case. public static void SyncLDAPWithMySql(Novell.Directory.Ldap.LdapConnection _conn) { List<User> users = GetUsers(); int iteller = 0; foreach (User user in users) { if (!UserAlreadyInLdap(user, _conn)) { TelUser teluser = new TelUser(); teluser.Telephone = user.E164; teluser.Uid = user.E164; teluser.Company = "/"; teluser.Dn = ""; teluser.Name = "/"; teluser.DisplayName = "/"; teluser.FirstName = "/"; TelephoneDA.InsertUser(_conn, teluser ); } Console.WriteLine(iteller + " : " + user.E164); iteller++; } } private static bool UserAlreadyInLdap(User user, Novell.Directory.Ldap.LdapConnection _conn) { List<TelUser> users = TelephoneDA.GetAllEntries(_conn); foreach (TelUser teluser in users) { if (teluser.Telephone.Equals(user.E164)) return true; } return false; } public static int InsertUser(LdapConnection conn, TelUser user) { int iResponse = IsTelNumberUnique(conn, user.Dn, user.Telephone); if (iResponse == 0) { LdapAttributeSet attrSet = MakeAttSet(user); string dnForPhonebook = configurationManager.AppSettings.Get("phonebookDn"); LdapEntry ent = new LdapEntry("uid=" + user.Uid + "," + dnforPhonebook, attrSet); try { conn.Add(ent); } catch (Exception ex) { Console.WriteLine(ex.Message); } } return iResponse; } Am i adding too many entries at a time??? Thanks in advance.

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  • django form ModelChoiceField loads all state names while needed states which are mapped with current selected country

    - by Sonu
    I am using modelChoiceField to display country and state into address form class StateSelectionwidget(forms.Select): """ custom widget to state selection""" class Media: js = ('media/javascript/public/jquery-1.5.2.min.js', 'media/javascript/public/countrystateselection.js', ) class AddressForm(forms.Form): name = forms.CharField(max_length=30) country = forms.ModelChoiceField(queryset=[]) state = forms.ModelChoiceField(CountryState.objects, widget=StateSelectionwidget) def __init__(self, *args, **kwargs): super(AddressForm, self).__init__(*args, **kwargs) self.fields['country'].queryset = Country.objects.all() Country model is used to store country names. CountryState model is used to store all states which is foreign key to Country model At the time of form loading i am getting all state names in dropdown while i want field to be blank by default. If name field is empty at the time of form save i am getting error that name can not be empty but also getting all states into dropdown list while i want only the states which are mapped with current selected country.

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  • Architecture of a single-page JavaScript web application?

    - by fig-gnuton
    How should a complex single-page JS web application be structured on the client-side? Specifically I'm curious about how to cleanly structure the application in terms of its model objects, UI components, any controllers, and objects handling server persistence. MVC seemed like a fit at first. But with UI components nested at various depths (each with their own way of acting on/reacting to model data, and each generating events which they themselves may or may not handle directly), it doesn't seem like MVC can be cleanly applied. (But please correct me if that's not the case.) -- (This question resulted in two suggestions of using ajax, which is obviously needed for anything other than the most trivial one-page app.)

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  • a completely decoupled OO system ?

    - by shrini1000
    To make an OO system as decoupled as possible, I'm thinking of the following approach: 1) we run an RMI/directory like service where objects can register and discover each other. They talk to this service through an interface 2) we run a messaging service to which objects can publish messages, and register subscription callbacks. Again, this happens through interfaces 3) when object A wants to invoke a method on object B, it discovers the target object's unique identity through #1 above, and publishes a message on the message service for object B 4) message services invokes B's callback to give it the message 5) B processes the request and sends the response for A on message service 6) A's callback is called and it gets the response. I feel this system is as decoupled as practically possible, but it has the following problems: 1) communication is typically asynchronous 2) hence it's non real time 3) the system as a whole is less efficient. Are there any other practical problems where this design obviously won't be applicable ? What are your thoughts on this design in general ?

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  • PHP Type Hinting: array supported, object NOT?

    - by Marius Burz
    Am I missing something or there really is no support for generic object type hinting in PHP 5.x? I find it really strange that hinting arrays is supported while hinting objects is not, at least not out of the box. I'd like to have something like this: function foo(object $o) Just as we have: function foo(array $o) Example of possible use: methods of an objects collection class. Workaround: using an interface "Object" implemented by all classes or extending all classes from a generic class "Object" and writing something like this: function foo(Object $o) Well, that just ain't cute. Edit: somebody suggested in a deleted post using stdClass. It doesn't work: Catchable fatal error: Argument 1 passed to c::add() must be an instance of stdClass, instance of b given

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  • Garbage Collection Java

    - by simion
    On the slides i am revising from it says the following; Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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  • Is a many-to-many relationship with extra fields the right tool for my job?

    - by whichhand
    Previously had a go at asking a more specific version of this question, but had trouble articulating what my question was. On reflection that made me doubt if my chosen solution was correct for the problem, so this time I will explain the problem and ask if a) I am on the right track and b) if there is a way around my current brick wall. I am currently building a web interface to enable an existing database to be interrogated by (a small number of) users. Sticking with the analogy from the docs, I have models that look something like this: class Musician(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) dob = models.DateField() class Album(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) class Instrument(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) Where I have one central table (Musician) and several tables of associated data that are related by either ForeignKey or OneToOneFields. Users interact with the database by creating filtering criteria to select a subset of Musicians based on data the data on the main or related tables. Likewise, the users can then select what piece of data is used to rank results that are presented to them. The results are then viewed initially as a 2 dimensional table with a single row per Musician with selected data fields (or aggregates) in each column. To give you some idea of scale, the database has ~5,000 Musicians with around 20 fields of related data. Up to here is fine and I have a working implementation. However, it is important that I have the ability for a given user to upload there own annotation data sets (more than one) and then filter and order on these in the same way they can with the existing data. The way I had tried to do this was to add the models: class UserDataSets(models.Model): user = models.ForeignKey(User) name = models.CharField(max_length=100) description = models.CharField(max_length=64) results = models.ManyToManyField(Musician, through='UserData') class UserData(models.Model): artist = models.ForeignKey(Musician) dataset = models.ForeignKey(UserDataSets) score = models.IntegerField() class Meta: unique_together = (("artist", "dataset"),) I have a simple upload mechanism enabling users to upload a data set file that consists of 1 to 1 relationship between a Musician and their "score". Within a given user dataset each artist will be unique, but different datasets are independent from each other and will often contain entries for the same musician. This worked fine for displaying the data, starting from a given artist I can do something like this: artist = Musician.objects.get(pk=1) dataset = UserDataSets.objects.get(pk=5) print artist.userdata_set.get(dataset=dataset.pk) However, this approach fell over when I came to implement the filtering and ordering of query set of musicians based on the data contained in a single user data set. For example, I could easily order the query set based on all of the data in the UserData table like this: artists = Musician.objects.all().order_by(userdata__score) But that does not help me order by the results of a given single user dataset. Likewise I need to be able to filter the query set based on the "scores" from different user data sets (eg find all musicians with a score 5 in dataset1 and < 2 in dataset2). Is there a way of doing this, or am I going about the whole thing wrong?

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