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• Backwards compatibility when using Core Data

  - by Alex

  Could anybody shed some light as to why is my app crashing with the following error on iPhone OS 2.2.1 dyld: Symbol not found: _OBJC_CLASS_$_NSPredicate Referenced from: /var/mobile/Applications/456F243F-468A-4969-9BB7-A4DF993AE89C/AppName.app/AppName Expected in: /System/Library/Frameworks/Foundation.framework/Foundation I have weak linked CoreData.framework, and have the Base SDK set to 3.0 and Deployment Target set to SDK 2.2 The app already uses other 3.0 features when available and I did not have any problems with those. But apparently the backward-compatibility methods used for other features do not work with Core Data. The app crashes before app delegate's applicationDidFinishLaunching gets called. Here's the debugger log: [Session started at 2010-05-25 20:17:03 -0400.] GNU gdb 6.3.50-20050815 (Apple version gdb-1119) (Thu May 14 05:35:37 UTC 2009) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "--host=i386-apple-darwin --target=arm-apple-darwin".tty /dev/ttys001 Loading program into debugger… sharedlibrary apply-load-rules all warning: Unable to read symbols from "MessageUI" (not yet mapped into memory). warning: Unable to read symbols from "CoreData" (not yet mapped into memory). Program loaded. target remote-mobile /tmp/.XcodeGDBRemote-12038-42 Switching to remote-macosx protocol mem 0x1000 0x3fffffff cache mem 0x40000000 0xffffffff none mem 0x00000000 0x0fff none run Running… [Switching to thread 10755] [Switching to thread 10755] Re-enabling shared library breakpoint 1 Re-enabling shared library breakpoint 2 Re-enabling shared library breakpoint 3 Re-enabling shared library breakpoint 4 Re-enabling shared library breakpoint 5 (gdb) continue warning: Unable to read symbols for ""/Users/alex/iPhone Projects/AppName/build/Debug-iphoneos"/AppName.app/AppName" (file not found). dyld: Symbol not found: _OBJC_CLASS_$_NSPredicate Referenced from: /var/mobile/Applications/456F243F-468A-4969-9BB7-A4DF993AE89C/AppName.app/AppName Expected in: /System/Library/Frameworks/Foundation.framework/Foundation (gdb)

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• Where to put data management rules for complex data validation in ASP.NET MVC?

  - by TheRHCP

  Hello, I am currently working on an ASP.NET MVC2 project. This is the first time I am working on a real MVC web application. The ASP.NET MVC website really helped me to get started really fast, but I still have some obscure knowledge concerning datamodel validation. My problem is that I do not really know where to manage my filled datamodel when it comes to complex validation rules. For example, validating a string field with a Regex is quite easy and I know that I just have to decorate my field with a specific attribute, so data management rules are implemented in the model. But if I have multiple fields that I need to validate which each other, for example multiple datetime that need to be correctly set following a specific time rule, where do I need to validate them? I know that I could create my own validation attributes, but sometimes validation ask a specific validation path which is to complex to be validated using attributes. This first question also leads me to a related question which is, is it right to validate a model in the controller? Because for the moment that is the only way I found for complex validation. But I find this a bit dirty and I feel it does not really fit a the controller role and much harder to test (multiple code path). Thanks.

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• VB.NET handling data between different forms

  - by niuchu

  Hi, I'm writing a simple application - address book. User enters new addresses and they are added as an entry to a list visible on the main form (frmStart). I use one form to add and edit (AddContForm). Add button on the frmStart works fine, however I experience some problems with the edit button as when I press it and enter new data they are added as new entry however the previous entry is still there. Logic is handled by Contact.vb class. Please let me know how to fix this problem. Here is the code: Contact.vb Public Class Contact Public Contact As String Public Title As String Public Fname As String Public Surname As String Public Address As String Private myCont As String Public Property Cont() Get Return myCont End Get Set(ByVal value) myCont = Value End Set End Property Public Overrides Function ToString() As String Return Me.Cont End Function Public Sub Display() Dim C As New Contact C.Cont = frmAddCont.txtTitle.Text C.Fname = frmAddCont.txtFName.Text C.Surname = frmAddCont.txtSName.Text C.Address = frmAddCont.txtAddress.Text frmStart.lstContact.Items.Add(C) End Sub End Class Here is frmStart.vb Public Class frmStart Public Button As String Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click Button = "" Button = "Add" frmAddCont.ShowDialog() End Sub Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDel.Click Button = "" Button = "Del" Dim DelCont As Contact DelCont = Me.lstContact.SelectedItem() lstContact.Items.Remove(DelCont) End Sub Private Sub lstContact_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lstContact.SelectedIndexChanged End Sub Private Sub btnEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEdit.Click Button = "" Button = "Edit" Dim C As Contact If lstContact.SelectedItem IsNot Nothing Then C = DirectCast(lstContact.SelectedItem, Contact) frmAddCont.ShowDialog() End If End Sub End Class Here is AddContFrm.vb Public Class frmAddCont Public Class ControlObject Dim Title As String Dim FName As String Dim SName As String Dim Address As String Dim TelephoneNumber As Integer Dim emailAddress As String Dim Website As String Dim Photograph As String End Class Private Sub btnConfirmAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConfirmAdd.Click Dim B As String B = frmStart.Button Dim C As New Contact C.Display() Me.Hide() If B = "Edit" Then C = DirectCast(frmStart.lstContact.SelectedItem, Contact) frmStart.lstContact.SelectedItems.Remove(C) End If End Sub Private Sub frmAddCont_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load End Sub End Class

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• Core data setReturnsDistinctResult not working

  - by Moze

  So i'm building a small application, it uses core data database of ~25mb size with 4 entities. It's for bus timetables. In one table named "Stop" there are have ~1300 entries of bus stops with atributes "name", "id", "longitude", "latitude" and couple relationships. Now there are many stops with same name but different coordinates and id. Search is implemented using NSPredicate. So I want to show all distinct stop names in table view, i'm using setReturnsDistinctResults with NSDictionaryResultType and setPropertiesToFetch. But setReturnsDistinctResult is not working and I'm still getting all entries. Heres code: - (NSFetchRequest *)fetchRequest { if (fetchRequest == nil) { fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Stop" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; NSArray *sortDescriptors = [NSArray arrayWithObject:[[[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES] autorelease]]; [fetchRequest setSortDescriptors:sortDescriptors]; [fetchRequest setResultType:NSDictionaryResultType]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:[[entity propertiesByName] objectForKey:@"name"]]]; [fetchRequest setReturnsDistinctResults:YES]; DebugLog(@"fetchRequest initialized"); } return fetchRequest; } ///////////////////// - (NSFetchedResultsController *)fetchedResultsController { if (self.predicateString != nil) { self.predicate = [NSPredicate predicateWithFormat:@"name CONTAINS[cd] %@", self.predicateString]; [self.fetchRequest setPredicate:predicate]; } else { self.predicate = nil; [self.fetchRequest setPredicate:predicate]; } fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:self.fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:sectionNameKeyPath cacheName:nil]; return fetchedResultsController; } ////////////// - (UITableViewCell *)tableView:(UITableView *)table cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } cell.textLabel.text = [[fetchedResultsController objectAtIndexPath:indexPath] valueForKey:@"name"]; return cell; }

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• how to continuously send data without blocking?

  - by Donal Rafferty

  I am trying to send rtp audio data from my Android application. I currently can send 1 RTP packet with the code below and I also have another class that extends Thread that listens to and receives RTP packets. My question is how do I continuously send my updated buffer through the packet payload without blocking the receiving thread? public void run() { isRecording = true; android.os.Process.setThreadPriority (android.os.Process.THREAD_PRIORITY_URGENT_AUDIO); int buffersize = AudioRecord.getMinBufferSize(8000, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT); Log.d("BUFFERSIZE","Buffer size = " + buffersize); arec = new AudioRecord(MediaRecorder.AudioSource.MIC, 8000, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, buffersize); short[] readBuffer = new short[80]; byte[] buffer = new byte[160]; arec.startRecording(); while(arec.getRecordingState() == AudioRecord.RECORDSTATE_RECORDING){ int frames = arec.read(readBuffer, 0, 80); @SuppressWarnings("unused") int lenghtInBytes = codec.encode(readBuffer, 0, buffer, frames); RtpPacket rtpPacket = new RtpPacket(); rtpPacket.setV(2); rtpPacket.setX(0); rtpPacket.setM(0); rtpPacket.setPT(0); rtpPacket.setSSRC(123342345); rtpPacket.setPayload(buffer, 160); try { rtpSession2.sendRtpPacket(rtpPacket); } catch (UnknownHostException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (RtpException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } So when I send on one device and receive on another I get decent audio, but when I send and receive on both I get broken sound like its taking turns to send and receive audio. I have a feeling it could be to do with the while loop? it could be looping around in there and not letting anything else run?

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• Core Data Inferred Migration – Automatic "lightweight" vs Manual

  - by ohhorob

  I've updated the model of an existing iPhone app in some simple ways (remove attribute, add attribute, remove index), and can use automatic lightweight migration to migrate the persistent store. Due to the typical size of the data set, the processing time is not insignificant, and warrants feedback for the user. NSMigrationManager provides a simple but useful migrationProgress value that sends KVO notifications as the migration is performed. That forms the basis of providing feedback, however attempting to use an inferred model ([NSMappingModel inferredMappingModelForSourceModel:destinationModel:error:]) results in drastically different timing for the exact same dataset. Profile results on and original iPhone (2G) Automatic inferred lightweight migration PROFILE: CacheManager -migrateStore PROFILE: 0.6130 (+0.6130) models loaded PROFILE: 1.1759 (+0.5629) delegate -CacheManagerWillMigrate: PROFILE: 1.2516 (+0.0757) persistent store coordinator loaded PROFILE: 5.1436 (+3.8920) automatic lightweight migration completed PROFILE: 5.5435 (+0.3999) delegate -CacheManagerDidFinishMigration:withError: Manual inferred migration PROFILE: CacheManager -migrateStore PROFILE: 0.6660 (+0.6660) models loaded PROFILE: 1.1471 (+0.4811) inferred mapping model generated PROFILE: 1.4046 (+0.2574) delegate -CacheManagerWillMigrate: PROFILE: 1.5058 (+0.1013) persistent store coordinator loaded PROFILE: 22.6952 (+21.1894) manual migration completed PROFILE: 23.1478 (+0.4525) delegate -CacheManagerDidFinishMigration:withError: So, with an inferred model, the manual migration takes over 5 times longer than automatic! It's a big inconsistency, and the lightweight option that NSPersistentStoreCoordinator -addPersistentStoreWithType:configuration:URL:options:error: provides absolutely no indication of progress while processing. Can anybody provide a supported way to get the migrationProgress values during automatic migration, OR a way to configure an inferred mapping model to be as fast during manual processing as automatic?

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• Core Data @sum aggregate

  - by nasim

  I am getting an exception when I try to get @sum on a column in iPhone Core-Data application. My two models are following - Task model: @interface Task : NSManagedObject { } @property (nonatomic, retain) NSString * taskName; @property (nonatomic, retain) NSSet* completion; @end @interface Task (CoreDataGeneratedAccessors) - (void)addCompletionObject:(NSManagedObject *)value; - (void)removeCompletionObject:(NSManagedObject *)value; - (void)addCompletion:(NSSet *)value; - (void)removeCompletion:(NSSet *)value; @end Completion model: @interface Completion : NSManagedObject { } @property (nonatomic, retain) NSNumber * percentage; @property (nonatomic, retain) NSDate * time; @property (nonatomic, retain) Task * task; @end And here is the fetch: NSFetchRequest *request = [[NSFetchRequest alloc] init]; request.entity = [NSEntityDescription entityForName:@"Task" inManagedObjectContext:context]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"taskName" ascending:YES]; request.sortDescriptors = [NSArray arrayWithObject:sortDescriptor]; NSError *error; NSArray *results = [context executeFetchRequest:request error:&error]; NSArray *parents = [results valueForKeyPath:@"taskName"]; NSArray *children = [results valueForKeyPath:@"[email protected]"]; NSLog(@"%@ %@", parents, children); [request release]; [sortDescriptor release]; The exception is thrown at the fourth line from bottom. The thrown exception is: *** -[NSCFSet decimalValue]: unrecognized selector sent to instance 0x3b25a30 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSCFSet decimalValue]: unrecognized selector sent to instance 0x3b25a30' I would very much appreciate any kind of help. Thanks.

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• Windows Phone app: Binding data in a UserControl which is contained in a ListBox

  - by Alexandros Dafkos

  I have an "AddressListBox" ListBox that contains "AddressDetails" UserControl items, as shown in the .xaml file extract below. The Addresses collection is defined as ObservableCollection< Address Addresses and Street, Number, PostCode, City are properties of the Address class. The binding fails, when I use the "{Binding property}" syntax shown below. The binding succeeds, when I use the "dummy" strings in the commented-out code. I have also tried "{Binding Path=property}" syntax without success. Can you suggest what syntax I should use for binding the data in the user controls? <ListBox x:Name="AddressListBox" DataContext="{StaticResource dataSettings}" ItemsSource="{Binding Path=Addresses, Mode=TwoWay}"> <ListBox.ItemTemplate> <DataTemplate> <!-- <usercontrols:AddressDetails AddressRoad="dummy" AddressNumber="dummy2" AddressPostCode="dummy3" AddressCity="dummy4"> </usercontrols:AddressDetails> --> <usercontrols:AddressDetails AddressRoad="{Binding Street}" AddressNumber="{Binding Number}" AddressPostCode="{Binding PostCode}" AddressCity="{Binding City}"> </usercontrols:AddressDetails> </DataTemplate> </ListBox.ItemTemplate> </ListBox>

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• NSUndoManager, Core Data and selective undo/redo

  - by Combat

  I'm working on a core data application that has a rather large hierarchy of managed objects similar to a tree. When a base object is created, it creates a few child objects which in turn create their own child objects and so on. Each of these child objects may gather information using NSURLConnections. Now, I'd like to support undo/redo with the undoManager in the managedObjectContext. The problem is, if a user creates a base object, then tries to undo that action, the base object is not removed. Instead, one or more of the child objects may be removed. Obviously this type of action is unpredictable and unwanted. So I tried disabling undo registration by default. I did this by calling disableUndoRegistration: before anything is modified in the managedObjectContext. Then, enabling undo registration before base operations such as creating a base object the again re-disabling registrations afterwords. Now when i try to undo, I get this error: undo: NSUndoManager 0x1026428b0 is in invalid state, undo was called with too many nested undo groups Thoughts?

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• What is SSIS order of data transformation component method calls

  - by Ron Ruble

  I am working on a custom data transformation component. I'm using NUnit and NMock2 to test as I code. Testing and getting the custom UI and other features right is a huge pain, in part because I can't find any documentation about the order in which SSIS invokes methods on the component at design time as well as runtime. I can correct the issues readily enough, but it's tedious and time consuming to unregister the old version, register the new version, fire up the test ssis package, try to display the UI, get an obscure error message, backtrace it, modify the component and continue. One of the big issues involves the UI component needing access to the componentmetadata and buffermanager properties of the component at design time, and what I need to provide for to support properties that won't be initialized until after the user enters them in the UI. I can work through it; but if someone knows of some docs or tips that would speed me up, I'd greatly appreciate it. The samples I've found havn't been much use; they seem to be directed to showing off cool stuff (Twitter, weather.com) rather than actual work. Thanks in advance.

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• Core Data - 'calculated' attributes

  - by nephilim

  I have two entities: A and B A has two properties from and to, both pointing to the B entity. B as a fetched property to A with predicate from == $FETCH_SOURCE or to = $FETCH_SOURCE -- (from) -> A -- (to) -> B <- (As) -- In my application I select a certain B instance, and then show all of its A instances. Now, in my table the columns are bound to an array controller containing the selected A instances. I want to 'merge' the from and to columns. I already know one of the columns will be equal to the selected B instance, so now I'm only interested in the second value. The options I see: create a custom class for the B entity and create a method that returns either value. It should somehow be able to retrieve which B instance is currently selected. create a custom DataSource. Most columns are still using bindings, so then we'd have to access the NSArrayController's array so we're sure we have the right object. create a custom DataSource, remove the NSArrayController and do all the Core Data stuff ourselves. Is there any 'right' way to solve this?

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• getting data from tableviewcell to 2nd view

  - by chubsta

  I am very new to this and am trying to learn by creating a few little apps for myself. I have a navigation-based app where the user taps the row to select a film title - i then want the second view to show details of the film. Thanks to a very helpful person here i am getting the results of the row pressed as 'rowTitle' as follows : (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSString *key = [keys objectAtIndex:indexPath.section]; NSArray *nameSection = [names objectForKey:key]; NSString *rowTitle = [nameSection objectAtIndex:indexPath.row]; NSLog(@"rowTitle = %@", rowTitle); [tableView deselectRowAtIndexPath:indexPath animated:YES]; I am, however, struggling to make the data at 'rowTitle' available to the 2nd view - basically, if i can get the info - for example rowTitle is "aliens2" - i want to be able to add a new extension to the end of the string returned by 'rowTitle' in order to point to an image (if that makes sense) in the second view... something like tempImageName=[** this is where the info from rowTitle needs to be i suppose**]; tempImageType=@".png"; finalImageName=[tempImageName stringByAppendingString:tempImageType]; does this make sense to anyone (apologies if it doesnt - i know what i want but how to explain it is a little more awkward!) Thanks again for any help anyone can give (and any help as to formatting these questions would be useful too obviously!!)!

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• Core Data: Overkill for simple, static UITableView-based iPhone App?

  - by David Foster

  Hello! I have a rather simple iPhone app consisting of numerous views containing a single, grouped table view. These views are held together in navigation controllers which are grouped in a tab bar. Simple stuff. My table views do little more than list text (like "Dog", "Cat" and "Weasel") and this data is being served from a collection of plists. It's perhaps worth mentioning too that these tables are 'static' in the sense that their data is pre-determined and will only ever be amended—and if so, very rarely indeed—by the developer (in this case, moi). This rudimentary approach has reached its limits though, and I think I'm going to need something a bit more relational. I have worked a tad with Core Data in the past, but only with apps whose data is determined by user input. I have four closely related questions: Is Core Data overkill for an app consisting mainly of a selection of simple table views? Do you recommend using Core Data to manage data which is predetermine and extremely unlikely to ever change? Can one lock Core Data down so that its data can't change, thereby relinquishing my responsibility as the developer to handle the editing and saving of the managed object context? How do I go about giving Core Data my predetermined data, and in a format I know that it can work with? Thanks a bunch guys.

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• Core Data: Deleting causes 'NSObjectInaccessibleException' from NSOperation with a reference to a deleted object

  - by Bryan Irace

  My application has NSOperation subclasses that fetch and operate on managed objects. My application also periodically purges rows from the database, which can result in the following race condition: An background operation fetches a bunch of objects (from a thread-specific context). It will iterate over these objects and do something with their properties. A bunch of rows are deleted in the main managed object context. The background operation accesses a property on an object that was deleted from the main context. This results in an 'NSObjectInaccessibleException', reason: 'CoreData could not fulfill a fault' Ideally, the objects that are fetched by the NSOperation can be operated on even if one is deleted in the main context. The best way I can think to achieve this is either to: Call [request setReturnsObjectsAsFaults:NO] to ensure that Core Data won't try to fulfill a fault for an object that no longer exists in the main context. The problem here is I may need to access the object's relationships, which (to my understanding) will still be faulted. Iterate through the managed objects up front and copy the properties I will need into separate non-managed objects. The problem here is that (I think) I will need to synchronize/lock this part, in case an object is deleted in the main context before I can finish copying. Am I missing something obvious? It doesn't seem like what I'm trying to accomplish is too out of the ordinary. Thanks for your help.

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• Core Data: migrating entities with self-referential properties

  - by Dan

  My Core Data model contains an entity, Shape, that has two self-referential relationships, which means four properties. One pair is a one-to-many relationship (Shape.containedBy <- Shape.contains) and the another is a many-to-many relationship (Shape.nextShapes <<- Shape.previousShapes). It all works perfectly in the application, so I don't think self-referencing relationships is a problem in general. However, when it comes to migrating the model to a new version, then Xcode fails to compile the automatically generated mapping model, with this error message: 2009-10-30 17:10:09.387 mapc[18619:607] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse the format string "FUNCTION($manager ,'destinationInstancesForSourceRelationshipNamed:sourceInstances:' , 'contains' , $source.contains) == 1"' *** Call stack at first throw: ( 0 CoreFoundation 0x00007fff80d735a4 __exceptionPreprocess + 180 1 libobjc.A.dylib 0x00007fff83f0a313 objc_exception_throw + 45 2 Foundation 0x00007fff819bc8d4 _qfqp2_performParsing + 8412 3 Foundation 0x00007fff819ba79d +[NSPredicate predicateWithFormat:arguments:] + 59 4 Foundation 0x00007fff81a482ef +[NSExpression expressionWithFormat:arguments:] + 68 5 Foundation 0x00007fff81a48843 +[NSExpression expressionWithFormat:] + 155 6 XDBase 0x0000000100038e94 -[XDDevRelationshipMapping valueExpressionAsString] + 260 7 XDBase 0x000000010003ae5c -[XDMappingCompilerSupport generateCompileResultForMappingModel:] + 2828 8 XDBase 0x000000010003b135 -[XDMappingCompilerSupport compileSourcePath:options:] + 309 9 mapc 0x0000000100001a1c 0x0 + 4294973980 10 mapc 0x0000000100001794 0x0 + 4294973332 ) terminate called after throwing an instance of 'NSException' Command /Developer/usr/bin/mapc failed with exit code 6 The 'contains' is the name of one of the self-referential properties. Anyway, the really big problem is that I can't even look at this Mapping Property as Xcode crashes as soon as I select the entity mapping when viewing the mapping model. So I'm a bit lost really where to go from here. I really can't remove the self-referential properties, so I'm thinking I've got manually create a mapping model that compiles? Any ideas? Cheers

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• Tree data in MySql database table

  - by Robert Koritnik

  I have a table that uses Adjacency list model for hierarchy storage. My most relevant columns in this table are therefore: ItemId // is auto_increment ParentId Level ParentTrail // in the form of "parentId/../parentId/itemId" then I created a before insert tigger, that populates columns Level and ParentTrail. Since the last column also includes current item's ID I had to use a trick in my trigger because auto_increment columns are not available in the before insert trigger. So I get that value from the information_schema.tables table. All works fine, until I try to write an update trigger, that would update my item and its descendants when the item changes its parent (ParentId has changed). But I can't make an update on my table inside the update trigger. All I can do is to change current record's values but not other's. I could use a separate table for hierarchy data, but that would mean that I would also have to create a view that would combine these two tables (1:1 relation) and I would like to avoid this is at all possible. Is there a way to have all these in the same table so that these fields (Level and ParetTrail) set/update themselves automagically using triggers?

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• Distinct Value Array for View Controller Index Using Core Data

  - by b.dot

  Hi, I'm trying to create an index representing the first letter value of each record in a Core Data store to be used in a table view controller. I'm using a snippet of the code from Apple's documentation. I would simply like to produce an array or dictionary of distinct values as the result. My store already has the character defined within each record object. Questions: 1) I'm having a problem understanding NSDictionaryResultType. Where does the resulting dictionary object get received so that I can assign it's keys to the view controller? The code seems to only return an array. 2) If I include the line containing NSDictionaryResultType, I get no returns. 3) I realize that I could do this in a loop, but I'm hoping this will work. Thanks! NSEntityDescription *entity = [NSEntityDescription entityForName:@"People" inManagedObjectContext:managedObjectContext]; NSFetchRequest *request = [[NSFetchRequest alloc] init]; [request setEntity:entity]; [request setResultType:NSDictionaryResultType]; // This line causes no no results. [request setReturnsDistinctResults:YES]; [request setPropertiesToFetch :[NSArray arrayWithObject:@"alphabetIndex"]]; NSError *error; NSArray *objects = [managedObjectContext executeFetchRequest:request error:&error];

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• Queue Data structure app crash with front() method

  - by Programer

  I am implementing queue data strcutre but my app gets crashed, I know I am doing something wrong with Node pointer front or front() method of queue class #include <iostream> using namespace std; class Node { public: int get() { return object; }; void set(int object) { this->object = object; }; Node * getNext() { return nextNode; }; void setNext(Node * nextNode) { this->nextNode = nextNode; }; private: int object; Node * nextNode; }; class queue{ private: Node *rear; Node *front; public: int dequeue() { int x = front->get(); Node* p = front; front = front->getNext(); delete p; return x; } void enqueue(int x) { Node* newNode = new Node(); newNode->set(x); newNode->setNext(NULL); rear->setNext(newNode); rear = newNode; } int Front() { return front->get(); } int isEmpty() { return ( front == NULL ); } }; main() { queue q; q.enqueue(2); cout<<q.Front(); system("pause"); }

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• Reading a C/C++ data structure in C# from a byte array

  - by Chris Miller

  What would be the best way to fill a C# struct from a byte[] array where the data was from a C/C++ struct? The C struct would look something like this (my C is very rusty): typedef OldStuff { CHAR Name[8]; UInt32 User; CHAR Location[8]; UInt32 TimeStamp; UInt32 Sequence; CHAR Tracking[16]; CHAR Filler[12];} And would fill something like this: [StructLayout(LayoutKind.Explicit, Size = 56, Pack = 1)]public struct NewStuff{ [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)] [FieldOffset(0)] public string Name; [MarshalAs(UnmanagedType.U4)] [FieldOffset(8)] public uint User; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)] [FieldOffset(12)] public string Location; [MarshalAs(UnmanagedType.U4)] [FieldOffset(20)] public uint TimeStamp; [MarshalAs(UnmanagedType.U4)] [FieldOffset(24)] public uint Sequence; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)] [FieldOffset(28)] public string Tracking;} What is best way to copy OldStuff to NewStuff, if OldStuff was passed as byte[] array? I'm currently doing something like the following, but it feels kind of clunky. GCHandle handle;NewStuff MyStuff;int BufferSize = Marshal.SizeOf(typeof(NewStuff));byte[] buff = new byte[BufferSize];Array.Copy(SomeByteArray, 0, buff, 0, BufferSize);handle = GCHandle.Alloc(buff, GCHandleType.Pinned);MyStuff = (NewStuff)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(NewStuff));handle.Free(); Is there better way to accomplish this?

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• Java data structure suggestion.

  - by techoverflow

  Hi folks, I am a newbie in this field so please excuse my silly mistakes :) So the issue I am facing is: On my webpage, I am displaying a table. For now my issue is concerned with three columns of the table. First is : Area Code Second is : Zone Code Third is: Value The relationship between these three is: 1 Area Code has 6 different Zone code's and all those 6 Zone codes have corresponding "Value" I need a data structer that would give me the flexibility to get a "Value" for a Zone code, which falls under a particular Area code. I have the same zone codes for all the Area codes: Zone codes are: 111, 222, 333, 444, 555, 666 After surfing your stackoverflow, I thought I can go with this structure: Map<Integer, Map<Integer, Double>> retailPrices = new HashMap<Integer, Map<Integer, Double>>(); Map<Integer, Double> codes = new HashMap<Integer, Double>(); where reatailPrices would hold an Area Code and a Map of Zone code as Key and "Value" as Value. but when I am trying to populate this through a SQL resultset, I am getting the following error: The method put(Integer, Map<Integer,Double>) in the type Map is not applicable for the arguments (Integer, Double) on line: `while(oResult.next()) retailPrices.put((new Integer(oResult.getString("AREA"))), (pegPlPrices.put(new Integer(oResult.getString("ZONE_CODE")), new Double(oResult.getString("VALUE"))))); }` please help me figure out this problem. Am I following the right approach?

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• NSFetchedResultsController didn't return data

  - by Dmitry Kochkin

  Hello! I get stuck in some problem and after 2 days of seeking I've found solution but didn't get idea why does it work. First, I'm initialized NSFetchedResultsController using following code (it look like a lot of automatically generated): - (NSFetchedResultsController *)fetchedResultsController { if (fetchedResultsController != nil) return fetchedResultsController; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Profile" inManagedObjectContext:self.managedObjectContext]; [fetchRequest setEntity:entity]; [fetchRequest setFetchBatchSize:20]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"lastName" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; NSError *error = nil; //[aFetchedResultsController performFetch:&error]; [aFetchedResultsController release]; [fetchRequest release]; [sortDescriptor release]; [sortDescriptors release]; return fetchedResultsController; } Have a look at commented string - there wasn't any of these strings and when I asked for data - I didn't get any (and it was there!). When I've uncommented that line, it starts work. Seems evident, but all examples I saw before hadn't that line. And they work. How can it be? I just want to know what am I doing wrong.

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• Missing tables on Scaffold Dynamic Data page

  - by Ben Amada

  I created a Linq-to-SQL DBML for the first time. I dragged and dropped all my tables over to the designer. The tables all appear in the designer.cs file. In Global.asax, I also have model.RegisterContext() with the ScaffoldAllTables = true option. The routes are also setup. I can pull up the Scaffolding page, but there's at least one table that is missing that I'm trying to get to show up. This missing table has a relationship with a child table that references it. The child table appears. When viewing data for the child table, the column that references the missing/parent table shows the numeric PK int value, rather than showing the "name". So instead of showing "Cars" it shows 1, and instead of showing "Planes" it shows 2, etc. There's another table in the DB that has the same type of structure as the missing table, and it is correctly appearing in the scaffolded tables. For this missing table, I've tried explicitly adding the ScaffoldTable attribute to no avail. Does anyone know what would cause a table like this to not appear in the list Scaffolded tables? Thanks very much.

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• Retrieving a unique result set with Core Data

  - by randombits

  I have a core data based app that manages a bunch of entities. I'm looking to be able to do the following. I have an entity "SomeEntity" with the attributes: name, type, rank, foo1, foo2. Now, SomeEntity has several rows if when we're speaking strictly in SQL terms. What I'm trying to accomplish is to retrieve only available types, even though each instance can have duplicate types. I also need them returned in order according to rank. So in SQL, what I'm looking for is the following: SELECT DISTINCT(type) ORDER BY rank ASC Here is the code I have so far that's breaking: NSError *error = NULL; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setReturnsDistinctResults:YES]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"type", @"rank", nil]]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"SomeEntity" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; // sort by rank NSSortDescriptor *rankDescriptor = [[NSSortDescriptor alloc] initWithKey:@"rank" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:rankDescriptor,nil]; [fetchRequest setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [rankDescriptor release]; NSArray *fetchResults = [managedObjectContext executeFetchRequest:fetchRequest error:&error]; [fetchRequest release]; return fetchResults; Right now that is crashing with the following: Invalid keypath section passed to setPropertiesToFetch:

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• Scientific Data processing(Graph comparison and interpretation)

  - by pinkynobrain

  Hi stackoverflow friends, I'm trying to write a program to automate one of my more boring and repetative work tasks. I have some programming experience but none with processing or interpreting large volumes of data so i am seeking your advice(both suggestions of techneques to try and also things to read to learn more about doing this stuff). I have a piece of equipment that monitors an experiment by taking repeated samples and displays the readings on its screen as a graph. The input of experiment can be altered and one of these changes should produce a change in a section of the graph which i currently identify by eye and is what im looking for in the experiment. I want to automate it so that a computer looks at a set of results and spots the experiment input that causes the change. I can already extract the results from the machine. Currently they results for a run are in the form of an integer array with the index being the sample number and the corresponding value being the measurement. The overall shape of the graph will be similar for each experiment run. The change im looking for will be roughly the same and will occur in approximatly the same place every time for the correct experiment input. Unfortunatly there are a few gotcha's that make this problem more difficult. There is some noise in the measuring process which mean there is some random variation in the measured values between different runs. Although the overall shape of the graph remains the same. The time the experiment takes varies slightly each run causing two effects. First, the a whole graph may be shifted slightly on the x axis relative to another runs graph. Second, individual features may appear slightly wider or narrower in different runs. In both these cases the variation isn't particularly large and you can assume that the only non random variation is caused by the correct input being found. Thank you for your time, Pinky

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• Data structure to build and lookup set of integer ranges

  - by actual

  I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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