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• Do I really need an ORM?

  - by alchemical

  We're about to begin development on a mid-size ASP.Net MVC 2 web site. For a typical page, we grab data and throw it up on the web page, i.e. there is not much pre-processing of the data before it is sent to the UI. We're now making the decision whether or not to use an ORM and if yes, which one. We had been looking at EF2 AKA EF4 (ASP.Net Entity Framework in VS 2010) as one possibility. However, I'm thinking a simple solution in this case may be just to use datatables. The reason being that we don't plan to move the data around or process it a lot once we fetch it, so I'm not sure there is that much value in having strongly-typed objects as DTOs. Also, this way we avoid mapping altogether, thereby I think simplifying the code and allowing for faster development. I should mention budget is an issue on this project, as well as speed of execution. We are striving for simplicity anywhere we can, both to keep the budget smaller, the schedule shorter, and performance fast. We haven't fully decided this yet, but are currently leaning towards no ORM. Will we be OK with the no ORM approach or is an ORM worth it?

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• How to implement Priority Queues in Python?

  - by dragosrsupercool

  Sorry for such a silly question but Python docs are confusing.. . Link 1: Queue Implementation http://docs.python.org/library/queue.html It says thats Queue has a contruct for priority queue. But I could not find how to implement it. class Queue.PriorityQueue(maxsize=0) Link 2: Heap Implementation http://docs.python.org/library/heapq.html Here they says that we can implement priority queues indirectly using heapq pq = [] # list of entries arranged in a heap entry_finder = {} # mapping of tasks to entries REMOVED = '<removed-task>' # placeholder for a removed task counter = itertools.count() # unique sequence count def add_task(task, priority=0): 'Add a new task or update the priority of an existing task' if task in entry_finder: remove_task(task) count = next(counter) entry = [priority, count, task] entry_finder[task] = entry heappush(pq, entry) def remove_task(task): 'Mark an existing task as REMOVED. Raise KeyError if not found.' entry = entry_finder.pop(task) entry[-1] = REMOVED def pop_task(): 'Remove and return the lowest priority task. Raise KeyError if empty.' while pq: priority, count, task = heappop(pq) if task is not REMOVED: del entry_finder[task] return task raise KeyError('pop from an empty priority queue' Which is the most efficient priority queue implementation in python? And how to implement it?

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• JPA : many-to-many - only one foreign key in the association table

  - by Julien

  Hi, I mapped two classes in a ManyToMany association with these annotations : @Entity @Inheritance(strategy=InheritanceType.TABLE_PER_CLASS) public abstract class TechnicalItem extends GenericBusinessObject implements Resumable{ @SequenceGenerator(name="TECHNICAL_ITEM_ID_GEN", sequenceName="TECHNICAL_ITEM_ID_SEQ") @Id @Column(name = "\"ID\"", nullable = false) @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "TECHNICAL_ITEM_ID_GEN") private int id; @ManyToMany(mappedBy = "referencePerformanceItems", fetch=FetchType.LAZY) private List testingRates; } @Entity @DiscriminatorValue("T") public class TestingRate extends Rate { @ManyToMany(fetch=FetchType.LAZY) @JoinTable(name="ecc.\"TESTING_RATE_TECHNICAL_ITEM\"", joinColumns = {@JoinColumn(name = "\"TESTING_RATE_ID\"")}, inverseJoinColumns = {@JoinColumn(name = "\"TECHNICAL_ITEM_ID\"")}) //@ManyToMany(mappedBy = "testingRates", fetch=FetchType.LAZY) private List referencePerformanceItems; } The sql generated for the association table creation is : create table ecc."TESTING_RATE_TECHNICAL_ITEM" ( "TESTING_RATE_ID" int4 not null, "TECHNICAL_ITEM_ID" int4 not null ); alter table ecc."TESTING_RATE_TECHNICAL_ITEM" add constraint FKC5D64DF6A2FE2698 foreign key ("TESTING_RATE_ID") references ecc."RATE"; There is no mention of the second foreign key "TECHNICAL_ITEM_ID" (the second part of the composite foreign key which should be in the association table). Is it a normal behaviour ? What should I do in the mapping if I want my 2 columns are 2 foreign keys referencing the primary keys of my 2 concerned tables. I use a PostGreSQL database and Hibernate as JPA provider. Thanks, Julien

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• Performance penalty of typecasting and boxing/unboxing types in C# when storing generic values

  - by kitsune

  I have a set-up similar to WPF's DependencyProperty and DependencyObject system. My properties however are generic. A BucketProperty has a static GlobalIndex (defined in BucketPropertyBase) which tracks all BucketProperties. A Bucket can have many BucketProperties of any type. A Bucket saves and gets the actual values of these BucketProperties... now my question is, how to deal with the storage of these values, and what is the penalty of using a typecasting when retrieving them? I currently use an array of BucketEntries that save the property values as simple objects. Is there any better way of saving and returning these values? Beneath is a simpliefied version: public class BucketProperty<T> : BucketPropertyBase { } public class Bucket { private BucketEntry[] _bucketEntries; public void SaveValue<T>(BucketProperty<T> property, T value) { SaveBucketEntry(property.GlobalIndex, value) } public T GetValue<T>(BucketProperty<T> property) { return (T)FindBucketEntry(property.GlobalIndex).Value; } } public class BucketEntry { private object _value; private uint _index; public BucketEntry(uint globalIndex, object value) { ... } }

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• NHibernate - joining on a subquery using ICriteria

  - by owensymes.mp

  I have a SQL query that I need to represent using NHibernate's ICriteria API. SELECT u.Id as Id, u.Login as Login, u.FirstName as FirstName, u.LastName as LastName, gm.UserGroupId_FK as UserGroupId, inner.Data1, inner.Data2, inner.Data3 FROM dbo.User u inner join dbo.GroupMember gm on u.Id = gm.UserAnchorId_FK left join ( SELECT di.UserAnchorId_FK, sum(di.Data1) as Data1, sum(di.Data2) as Data2, sum(di.Data3) as Data3 FROM dbo.DailyInfo di WHERE di.Date between '2009-04-01' and '2009-06-01' GROUP BY di.UserAnchorId_FK ) inner ON inner.UserAnchorId_FK = u.Id WHERE gm.UserGroupId_FK = 195 Attempts so far have included mapping 'User' and 'DailyInfo' classes (my entities) and making a DailyInfo object a property of the User object. However, how to map the foreign key relationship between them is still a mystery, ie <one-to-one></one-to-one> <one-to-many></one-to-many> <generator class="foreign"><param name="property">Id</param></generator> (!) Solutions on the web are generally to do with subqueries within a WHERE clause, however I need to left join on this subquery instead to ensure NULL values are returned for rows that do not join. I have the feeling that I should be using a Criteria for the outer query, then forming a 'join' with a DetachedCriteria to represent the subquery?

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• UIWebView not loading URL

  - by jerincbus

  I'm having trouble getting a UIWebView to load a URL that I'm sending to it. Before I get into my code I was wondering if URL has to start with "http://" or can it start with "www."? I'm using an IBAction to push a UIView on to the stack: (IBAction)goToWebView { WebViewController *webController = [[WebViewController alloc] initWithNibName:@"WebViewController" bundle:[NSBundle mainBundle]]; //set the strings webController.webTitle = [self Title]; webController.webURL = [self website]; //Push the new view on the stack [[self navigationController] pushViewController:webController animated:YES]; [webController release]; webController = nil; } Then here is my WebViewController.h file: @interface WebViewController : UIViewController { IBOutlet UIWebView *webView; NSString *webTitle; NSString *webURL; } @property (nonatomic, retain) IBOutlet UIWebView *webView; @property (nonatomic, retain) NSString *webTitle; @property (nonatomic, retain) NSString *webURL; here And my WebViewController.m file: - (void)viewDidLoad { [super viewDidLoad]; NSString *urlAddress = webURL; //Create a URL object. NSURL *url = [NSURL URLWithString:urlAddress]; //URL Requst Object NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; //Load the request in the UIWebView. [webView loadRequest:requestObj]; }

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• Custom Event - invokation list implementation considerations

  - by M.A. Hanin

  I'm looking for some pointers on implementing Custom Events in VB.NET (Visual Studio 2008, .NET 3.5). I know that "regular" (non-custom) Events are actually Delegates, so I was thinking of using Delegates when implementing a Custom Event. On the other hand, Andrew Troelsen's "Pro VB 2008 and the .NET 3.5 Platform" book uses Collection types in all his Custom Events examples, and Microsoft's sample codes match that line of thought. So my question is: what considerations should I have when choosing one design over the other? What are the pros and cons for each design? Which of these resembles the inner-implementation of "regular" events? Below is a sample code demonstrating the two designs. Public Class SomeClass Private _SomeEventListeners As EventHandler Public Custom Event SomeEvent As EventHandler AddHandler(ByVal value As EventHandler) _SomeEventListeners = [Delegate].Combine(_SomeEventListeners, value) End AddHandler RemoveHandler(ByVal value As EventHandler) _SomeEventListeners = [Delegate].Remove(_SomeEventListeners, value) End RemoveHandler RaiseEvent(ByVal sender As Object, ByVal e As System.EventArgs) _SomeEventListeners.Invoke(sender, e) End RaiseEvent End Event Private _OtherEventListeners As New List(Of EventHandler) Public Custom Event OtherEvent As EventHandler AddHandler(ByVal value As EventHandler) _OtherEventListeners.Add(value) End AddHandler RemoveHandler(ByVal value As EventHandler) _OtherEventListeners.Remove(value) End RemoveHandler RaiseEvent(ByVal sender As Object, ByVal e As System.EventArgs) For Each handler In _OtherEventListeners handler(sender, e) Next End RaiseEvent End Event End Class

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• Silverlight 3 - How to "refresh" a DataGrid content?

  - by Josimari Martarelli

  I have the following scenery: 1 using System; 2 using System.Windows; 3 using System.Windows.Controls; 4 using System.Windows.Documents; 5 using System.Windows.Ink; 6 using System.Windows.Input; 7 using System.Windows.Media; 8 using System.Windows.Media.Animation; 9 using System.Windows.Shapes; 10 using System.Collections.Generic; 11 12 namespace refresh 13 { 14 public partial class MainPage : UserControl 15 { 16 17 List c = new List(); 18 19 public MainPage() 20 { 21 // Required to initialize variables 22 InitializeComponent(); 23 c.Add(new Customer{ _nome = "Josimari", _idade = "29"}); 24 c.Add(new Customer{_nome = "Wesley", _idade = "26"}); 25 c.Add(new Customer{_nome = "Renato",_idade = "31"}); 26 27 this.dtGrid.ItemsSource = c; 28 } 29 30 private void Button_Click(object sender, System.Windows.RoutedEventArgs e) 31 { 32 c.Add(new Customer{_nome = "Maiara",_idade = "18"}); 33 } 34 35 } 36 37 public class Customer 38 { 39 public string _nome{get; set;} 40 public string _idade{get; set;} 41 } 42 } Where, dtGrid is my DataGrid control... The Question is: How to get the UI Updated after adding one more register to my list. I get to solve it setting the DataGrid's Item Source to "" and then setting to the list of Customer objects again, like that: 1 private void Button_Click(object sender, System.Windows.RoutedEventArgs e) 2 3 { 4 5 c.Add(new Customer{_nome = "Maiara",_idade = "18"}); 6 7 this.dtGrid.ItemsSource=""; 8 9 this.dtGrid.ItemsSource=c; 10 11 } 12 Is there a way to get the UI updated or the datagrid's itemsSource refreshed automatically after updating, altering or deleting an item from the list c ? Thank you, Josimari Martarelli

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• Capture keystrokes (e.g., function keys) while a messagebox is up

  - by FastAl

  We have a large WinForms app, and there is a built-in bug reporting system that can be activated during testing via the F5 Key. I am capturing the F5 key with .Net's PreFilterMessage system. This works fine on the main forms, modal dialog boxes, etc. Unfortunately, the program also displays windows messageboxes when it needs to. When there is a bug with that, e.g., wrong text in the messagebox or it shouldn't be there, the messagefilter isn't executed at all when the messagebox is up! I realize I could fix it by either rewriting my own messagebox routine, or kicking off a separate thread that polls GetAsyncKeyState and calls the error reporter from there. However I was hoping for a method that was less of a hack. Here's code that manifests the problem: Public Class Form1 Implements IMessageFilter Private Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Click MsgBox("now, a messagebox is up!") End Sub Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Application.AddMessageFilter(Me) End Sub Public Function PreFilterMessage(ByRef m As System.Windows.Forms.Message) _ As Boolean Implements IMessageFilter.PreFilterMessage Const VK_F5 As Int32 = &H74 Const WM_KEYDOWN As Integer = &H100 If m.Msg = WM_KEYDOWN And m.WParam.ToInt32 = VK_F5 Then ' In reality code here takes a screenshot, saves the program state, and shows a bug report interface ' IO.File.AppendAllText("c:\bugs.txt", InputBox("Describe the bug:")) End If End Function End Class Many thanks.

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• Custom RoleProvider: Can't insert record in UsersInRole Table

  - by mahr.g.mohyuddin

  Hi, I have implemented a LINQ to SQL based RoleProvider, when I assign role to a user following exception is thrown while AddUsersToRoles method is called. I have defined a composite primary key userid & roleId on this table, it still throwing this exception: Can't perform Create, Update or Delete operations on 'Table(UsersInRole)' because it has no primary key. My LinQ to SQL implementation of AddUsersToRoles method is as follows. It breaks at db.UsersInRoles.InsertOnSubmit(userInRole); using (RussarmsDataContext db = new RussarmsDataContext()) { List<UsersInRole> usersInRole = new List<UsersInRole>(); foreach (string username in usernames) { foreach (string rolename in rolenames) { UsersInRole userInRole = new UsersInRole(); object userId = ProvidersUtility.GetUserIdByUserName(username,applicationName); object roleId = ProvidersUtility.GetRoleIdByRoleName(rolename,applicationName); if (userId != null && roleId != null) { userInRole.UserId = (Guid)userId; userInRole.RoleId = (Guid)roleId; db.UsersInRoles.InsertOnSubmit(userInRole); } } } try { // db.UsersInRoles.InsertAllOnSubmit(usersInRole); db.SubmitChanges(); } catch (ChangeConflictException) { db.ChangeConflicts.ResolveAll(RefreshMode.OverwriteCurrentValues); db.SubmitChanges(); } } Any help will be appreciated. Thanks.

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• Django custom managers - how do I return only objects created by the logged-in user?

  - by Tom Tom

  I want to overwrite the custom objects model manager to only return objects a specific user created. Admin users should still return all objects using the objects model manager. Now I have found an approach that could work. They propose to create your own middleware looking like this: #### myproject/middleware/threadlocals.py try: from threading import local except ImportError: # Python 2.3 compatibility from django.utils._threading_local import local _thread_locals = local() def get_current_user(): return getattr(_thread_locals, 'user', None) class ThreadLocals(object): """Middleware that gets various objects from the request object and saves them in thread local storage.""" def process_request(self, request): _thread_locals.user = getattr(request, 'user', None) #### end And in the Custom manager you could call the get_current_user() method to return only objects a specific user created. class UserContactManager(models.Manager): def get_query_set(self): return super(UserContactManager, self).get_query_set().filter(creator=get_current_user()) Is this a good approach to this use-case? Will this work? Or is this like "using a sledgehammer to crack a nut" ? ;-) Just using: Contact.objects.filter(created_by= user) in each view doesn`t look very neat to me. EDIT Do not use this middleware approach !!! use the approach stated by Jack M. below After a while of testing this approach behaved pretty strange and with this approach you mix up a global-state with a current request. Use the approach presented below. It is really easy and no need to hack around with the middleware. create a custom manager in your model with a function that expects the current user or any other user as an input. #in your models.py class HourRecordManager(models.Manager): def for_user(self, user): return self.get_query_set().filter(created_by=user) class HourRecord(models.Model): #Managers objects = HourRecordManager() #in vour view you can call the manager like this and get returned only the objects from the currently logged-in user. hr_set = HourRecord.objects.for_user(request.user)

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• WCF for a shared data access

  - by Audrius

  Hi all, I have a little experience with WCF and would like to get your opinion/suggestion on how the following problem can be solved: A web service needs to be accessible from multiple clients simultaneously and service needs to return a result from a shared data set. The concrete project I'm working on has to store a list of IP addresses/ranges. This list will be queried by a bunch of web servers for a validation purposes and we speak of a couple of thousand or more queries per minute. My initial draft approach was to use Windows service as a WCF host with service contract implementing class that is decorated with ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple) that has a list object and a custom locking for accessing it. So basically I have a WCF service singleton with a list = shared data - multiple clients. What I do not like about it is that data and communication layers are merged into one and performance wise this doesn't feel "right". What I really really (- want is Windows service running an instance of IP list holding container class object, a second service running WCF service contract implementation and a way the latter querying the former in a nice way with a minimal blocking. Using another WCF channel would not really take me far away from the initial draft implementation or would it? What approach would you take? Project is still in a very early stage so complete design re-do is not out of question. All ideas are appreciated. Thanks! UPDATE: The data set will be changed dynamically. Web service will have a separate method to add IP or IP range and on top of that there will be a scheduled task that will trigger data cleanup every 10-15 minutes according to some rules. UPDATE 2: a separate benchmark project will be kicked up that should use MSSQL as a data backend (instead on in-memory list).

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• MATLAB Builder NE (.NET Assembly) Data type question

  - by Brett

  Hi coders, I am using MATLAB Builder NE (MATLAB's integrated .NET assmebly builder), but I am having an issue with data types. I have compiled a small, very simple, function in matlab and build it for .NET. I am able to call the namespace and even the function just fine. However, my function returns a value, and MATLAB defaults to returning it as an "object[]" data type. However, I know that the value is an integer, but I can't figure out how to cast it. My MATLAB function looks like this: function addValue = Myfunction(value1, value2) addValue=value1+value2; end Pretty simple right? And then in .NET I can call it as: xClass.addValue (1, 3, 4); where xClass is the name of the MATLAB built class but when I try: int x = xClass.addValue (1, 3, 4); C# errors out. Typical .NET casting (int) doesn't work. The compiler states it cannot convert object[] to int. Does anyone have experience with the .NET builder in MATLAB that can help me with this? It is really throwing me for a loop. I have scanned through most of the MATLAB BUILDER doc (484 pages!) with zero help. Thank you, Brett

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• Error when instantiating .NET/COM interop class via classic ASP

  - by Lee D

  Hi all, I am having a problem when trying to instantiate a C# .NET class that's been exposed to COM in a classic ASP application. I've used tlbexp to generate a typelib and registered it in Component Services; now when trying to create the object as such: Server.CreateObject("The.Class.Name") I am getting the error: Server object error 'ASP 0177 : 80131534' Server.CreateObject Failed I've searched around online for information on this error, and found numerous discussions but no solution. The error code 0x80131534 apparently means "COR_E_TYPEINITIALIZATION, a type failed to initialize", which would suggest the problem would be in the constructor. The constructor of the class in question sets a private field to an instance of another class from the same assembly, and then reads some configuration settings from an XML file. This behaviour is unit tested and I've checked that the file exists; I can't see anything else that could be breaking in there. A few other points which may or may not be of use: A test .NET project referencing the DLL can instantiate the class just fine; however a test VB6 project referencing the TLB blows up with the same error. Both the DLL and the TLB are in the same location. This application is running locally, on Windows XP Professional SP3 and IIS 5.1. The .NET assembly is built with .NET Framework 2.0, although 3.5 is installed on the machine. I know other people who don't get this error on their builds, so I believe it may be something environmental. Any suggestions are welcome as I've been struggling to fix this for some time. Thanks in advance.

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• Cookies not present after using XMLHttpRequest

  - by Joe B

  I'm trying to make a bookmarklet to download videos off of YouTube, but I've come across a little problem. To detect the highest quality video available, I use a sort of brute force method, in which I make requests using the XMLHttpRequest object until a 404 isn't returned (I can't do it until a 200 ok is returned because YouTube redirects to a different server if the video is available, and the cross-domain policy won't allow me to access any of that data). Once a working URL is found, I simply set window.location to the URL and the download should start, right? Wrong. A request is made, but for reasons unknown to me, the cookies are stripped and YouTube returns a 403 access denied. This does not happen if the XML requests aren't made before it, i.e. if I just set the window.location to the URL everything works fine, it's when I do the XMLHttpRequest that the cookies aren't sent. It's hard to explain so here's the script: var formats = ["37", "22", "35", "34", "18", ""]; var url = "/get_video?video_id=" + yt.getConfig('SWF_ARGS')['video_id'] + "&t=" + (unescape(yt.getConfig('SWF_ARGS')['t'])) + "&fmt="; for (var i = 0; i < formats.length; i++) { xmlhttp = new XMLHttpRequest; xmlhttp.open("HEAD", url + formats[i], false); xmlhttp.send(null); if (xmlhttp.status != 404) { document.location = url + formats[i]; break } } That script does not send the cookies after setting the document.location and thus does not work. However, simply doing this: document.location = /get_video?video_id=" + yt.getConfig('SWF_ARGS')['video_id'] + "&t=" + (unescape(yt.getConfig('SWF_ARGS')['t'])) DOES send the cookies along with the request, and does work. The only downside is I can't automatically detect the highest quality, I just have to try every "fmt" parameter manually until I get it right. So my question is: why is the XMLHttpRequest object removing cookies from subsequent requests? This is the first time I've ever done anything in JS by the way, so please, go easy on me. ;)

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• iPhone - return from an NSOperation

  - by lostInTransit

  Hi I am using a subclass of NSOperation to do some background processes. I want the operation to be cancelled when the user clicks a button. Here's what my NSOperation subclass looks like - (id)init{ self = [super init]; if(self){ //initialization code goes here _isFinished = NO; _isExecuting = NO; } return self; } - (void)start { if (![NSThread isMainThread]) { [self performSelectorOnMainThread:@selector(start) withObject:nil waitUntilDone:NO]; return; } [self willChangeValueForKey:@"isExecuting"]; _isExecuting = YES; [self didChangeValueForKey:@"isExecuting"]; //operation goes here } - (void)finish{ //releasing objects here [self willChangeValueForKey:@"isExecuting"]; [self willChangeValueForKey:@"isFinished"]; _isExecuting = NO; _isFinished = YES; [self didChangeValueForKey:@"isExecuting"]; [self didChangeValueForKey:@"isFinished"]; } - (void)cancel{ [self willChangeValueForKey:@"isCancelled"]; [self didChangeValueForKey:@"isCancelled"]; [self finish]; } And this is how I am adding objects of this class to a queue and listening for KVO notifications operationQueue = [[NSOperationQueue alloc] init]; [operationQueue setMaxConcurrentOperationCount:5]; [operationQueue addObserver:self forKeyPath:@"operations" options:0 context:&OperationsChangedContext]; - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if (context == &OperationsChangedContext) { NSLog(@"Queue size: %u", [[operationQueue operations] count]); } else { [super observeValueForKeyPath:keyPath ofObject:object change:change context:context]; } } To cancel an operation (on a button click for instance), I tried calling -cancel but it doesn't make a difference. Also tried calling -finish but even that doesn't change anything. Every time I add an operation to the queue, the queue size only increases. finish is called (checked using NSLog statements) but it doesn't really end the operation. I'm still not very confident I'm doing this right Can someone please tell me where I am going wrong? Thanks a lot

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• what's the alternative to readonlycollection when using lazy="extra"?

  - by Kunjan

  I am trying to use lazy="extra" for the child collection of Trades I have on my Client object. The trades is an Iset<Trade Trades, exposed as ReadOnlyCollection<Trade because I do not want anyone to modify the collection directly. As a result, I have added AddTrade and RemoveTrade methods. Now I have a Client Search page where I need to show the Trade Count. and on the Client details page I have a tab where I need to show all the trades for the Client in paged gridview. What I want to achieve is, for the search when I say on the client object as client.Trades.Count, nHibernate should only fire a select count(*) query. Hence I am using lazy="extra". But because I am using a ReadOnlyCollection, nHibernate fires a count query & a separate query to load the child collection trades completely. Also, I cannot include the Trades in my initial search request as this would disturb the paging because a counterparty can have n trades which would result in n rows, when I am searching clients only. So the child collections have to be loaded lazily. The second problem is that on the client details page -- Trades grid view, I have enabled paging for performance reasons. But by nature nHibernate loads the entire collection of trades as the user goes from one page to another. Ideally I want to control this by getting only trades specific to the page the user is on. How can I achieve this? I came across this very good article. http://stackoverflow.com/questions/876976/implementing-ipagedlistt-on-my-models-using-nhibernate But I am not sure if this will work for me, as lazy=extra currently doesnt work as expected with the ReadOnlyCollection. So, if I went ahead and implemented the solution this way and further enhanced it by making the List/Set Immutable, will lazy=extra give me the same problem as with ReadOnlyCollections?

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• Generic wrapper for System.Web.Caching.Cache functions

  - by David Neale

  I've created a generic wrapper for using the Cache object: public class Cache<T> where T : class { public Cache Cache {get;set;} public CachedKeys Key {get;set;} public Cache(Cache cache, CachedKeys key){ Cache = cache; Key = key; } public void AddToCache(T obj){ Cache.Add(Key.ToString(), obj, null, DateTime.Now.AddMinutes(5), System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.Normal, null); } public bool TryGetFromCache(out T cachedData) { cachedData = Cache[Key.ToString()] as T; return cachedData != null; } public void RemoveFromCache() { Cache.Remove(Key.ToString()); } } The CachedKeys enumeration is just a list of keys that can be used to cache data. The trouble is, to call it is quite convuluted: var cache = new Cache<MyObject>(Page.Cache, CachedKeys.MyKey); MyObject myObject = null; if(!cache.TryGetFromCache(out myObject)){ //get data... cache.AddToCache(data); //add to cache return data; } return myObject; I only store one instance of each of my objects in the cache. Therefore, is there any way that I can create an extension method that accepts the type of object to Cache and uses (via Reflection) its Name as the cache key? public static Cache<T> GetCache(this Cache cache, Type cacheType){ Cache<cacheType> Cache = new Cache<cacheType>(cache, cacheType.Name); } Of course, there's two errors here: Extension methods must be defined in a non-generic static class The type or namespace name 'cacheType' could not be found This is clearly not the right approach but I thought I'd show my working. Could somebody guide me in the right direction?

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• C++: Retriving values of static const variables at a constructor of a static variable

  - by gilbertc

  I understand that the code below would result segmentation fault because at the cstr of A, B::SYMBOL was not initialized yet. But why? In reality, A is an object that serves as a map that maps the SYMBOLs of classes like B to their respective IDs. C holds this map(A) static-ly such that it can provide the mapping as a class function. The primary function of A is to serve as a map for C that initializes itself at startup. How should I be able to do that without segmentation fault, provided that I can still use B::ID and B::SYMBOL in the code (no #define pls)? Thanks! Gil. class A { public: A() { std::cout<<B::ID<<std::endl; std::cout<<B::SYMBOL<<std::endl; } }; class B { public: static const int ID; static const std::string SYMBOL; } const int B::ID = 1; const std::string B::SYMBOL = "B"; class C { public: static A s_A; }; A C::s_A; int main(int c, char** p) { }

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• DataGridViewColumn.DataPropertyName Property

  - by Captain Comic

  Hi I have a DataGridView control and I want to populate it with data. I use DataSource property // dgvDealAsset is DataGridView private void DealAssetListControl_Load(object sender, EventArgs e) { dgvDealAssets.AutoGenerateColumns = false; dgvDealAssets.DataSource = DealAssetList.Instance.Values.ToList(); } Now problem number one. The class of my collection does not contain only simple types that I can map to columns using DataPropertyName. This is the class that is contained in collection. class MyClass { public String Name; MyOtherClass otherclass; } class MyOtherClass { public String Name; } Now I am binding properties of MyClass to columns col1.DataPropertyName = "Name" // Ok col2.DataPropertyName = "otherclass" // Not OK - I will have empty cell The problem is that I want to display otherclass.Name field. But if I try to write col2.DataPropertyName = "otherclass.Name" I get empty cell. I tried to manually set the column private void DealAssetListControl_Load(object sender, EventArgs e) { dgvDealAssets.AutoGenerateColumns = false; dgvDealAssets.DataSource = DealAssetList.Instance.Values.ToList(); // iterate through rows and set the column manually foreach (DataGridViewRow row in dgvDealAssets.Rows) { row.Cells["Column2"].Value = ((DealAsset)row.DataBoundItem).otherclass.Name; } But this foreach cycle takes about minute to complete (2k elements). How to solve this problem?

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• Which Computer Organization & Architecture book is good for me?

  - by claws

  I'm always interested in learning the inner working of things. I started with C programming and then learnt Operating systems (from stallings) and then linkers & loaders and then assembly language after reading these now I want to go into little more depth. Computer Architecture. I feel that makes everything clear. As per SO archives these are the two good books: Computer Architecture: A Quantitative Approach, 4th Edition Computer Organization and Design, Fourth Edition, ~ David A. Patterson, John L. Hennessy But I've browsed through the contents of these books and found that they don't exactly meet my needs. I want to learn more about caches, Memory Management Unit , mapping b/w virtual memory & physical memory I'm no way interested in other ISAs like MIPS etc.. I'm IA32 and X86-64 fan and I want to stick to it. I'm not a hardware developer I don't want to details like circuit diagrams or How is L1, L2 & L3 caches are implemented? I want to know the parallel processing technologies like HyperThreading at the architecture level but again I don't want to design them. I liked the table of Contents of - Computer Architecture: A Quantitative Approach, 4th Edition but Quantitave Approach? Seriously?? I want to know the details of current technologies and I dont want to spend reading 200 pages of outdated old technologies ( I experienced this while learning ASM}

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• AbstractMethodError when invoking createArrayOf, with postgresql 8.4 jdbc4 and JBoss 5.1GA

  - by Francesco

  Hi, when using this method public List<Field> getFieldWithoutId(List<Integer> idSections) throws Exception { try { Connection conn = this.getConnection(); Array arraySections = conn.createArrayOf("int4", idSections.toArray()); this.log.info("Recupero field"); List<Field> fields = this.getJdbcTemplate().query(getFieldWithoutIdQuery, new Object[] {arraySections},ParameterizedBeanPropertyRowMapper.newInstance(Field.class)); /*if (!conn.isClosed()) conn.close(); */ releaseConnection(conn); return fields; } catch (Exception e) { e.printStackTrace(); throw new Exception("Errore."); } } I have an exception at conn.createArrayOf("int4", idSections.toArray());. The exception is: javax.ejb.EJBException : Unexpected Error java.lang.AbstractMethodError: org.jboss.resource.adapter.jdbc.jdk5.WrappedConnectionJDK5.createArrayOf(Ljava/lang/String;[Ljava/lang/Object;)Ljava/sql/Array; postgresql-8.4-701.jdbc4.jar is in jboss/server/all/lib dir. Application is spring based with ejb3. When working locally with the same setup everything is fine. This only happens on a preproduction environment. Only difference is locally I have jboss run in default mode, in the other case there are 2 jbosses in all configuration. I can't track down the cause of this error. Could someone help me please?

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• Simulating aspects of static-typing in a duck-typed language

  - by Mike

  In my current job I'm building a suite of Perl scripts that depend heavily on objects. (using Perl's bless() on a Hash to get as close to OO as possible) Now, for lack of a better way of putting this, most programmers at my company aren't very smart. Worse, they don't like reading documentation and seem to have a problem understanding other people's code. Cowboy coding is the game here. Whenever they encounter a problem and try to fix it, they come up with a horrendous solution that actually solves nothing and usually makes it worse. This results in me, frankly, not trusting them with code written in duck typed language. As an example, I see too many problems with them not getting an explicit error for misusing objects. For instance, if type A has member foo, and they do something like, instance->goo, they aren't going to see the problem immediately. It will return a null/undefined value, and they will probably waste an hour finding the cause. Then end up changing something else because they didn't properly identify the original problem. So I'm brainstorming for a way to keep my scripting language (its rapid development is an advantage) but give an explicit error message when an an object isn't used properly. I realize that since there isn't a compile stage or static typing, the error will have to be at run time. I'm fine with this, so long as the user gets a very explicit notice saying "this object doesn't have X" As part of my solution, I don't want it to be required that they check if a method/variable exists before trying to use it. Even though my work is in Perl, I think this can be language agnostic.

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• One Model to Rule Them All - VS2010 UML, ADO.NET Entity Data Model, and T4

  - by Eric J.

  I worked on a fairly large project a while back where we modeled the classes in Enterprise Architect and generated the (partial) POCO classes (complete with model-driven business rule validations), persistence (NHibernate mapping file) and DDL. Based on certain model attributes we could flag alternate generation strategies or indicate that a particular portion would be entirely hand-coded. There was a good deal of initial investment, but it paid large dividends over the lifetime of a 15 developer, 3 year project. I'm investigating doing something similar with the current Microsoft technology stack. The place I'm stuck is that class modeling is done with the VS 2010 UML tools, but logical data modeling is done with Entity Data Modeler. Is it a reasonable path to use VS 2010 UML as the "single source of truth" and code generate the edmx files based on the class model? That's the inverse of the common path to create the entity model and use a POCO generator to generate classes. However, a good class model can be used to generate much more than just the properties so I tend to view it as a better choice than the entity model.

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• JQuery ajax request returns error and status 0

  - by Kucebe

  I use this pseudo-class to make ajax request to server: function RequestManager(url, params, success, error){ //save this ajax configuration this._ajaxCall = null; this._url= url; this._type = params.type; this._timer = params.timer || 0; this._success = function(){ alert("ok"); }; this._error = function(){ alert("ko"); }; } RequestManager.prototype = { require : function(tag){//here there will be a tag object in array format if(this.timer>0){ //wait this.timer } if(this.ajaxCall != null ){ this.ajaxCall.abort(); this.ajaxCall = null; } var self = this; this.ajaxCall = $.ajax({ url: this._url, type: this._type, data: tag, success: function(xmlResponse){ var responseArray = []; var response = _extractElements(xmlResponse, arrayResponse); self._success(response); }, error: self._error, complete : function(xhr, statusText){ alert(xhr.status); return null; } }); } When i instantiate a new object, and i use it to load a request, it always return to me error, and status code is 0. Server correctly generates an xml document. Why i can't get a correct 200 code back?

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