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  • Can a Generic Method handle both Reference and Nullable Value types?

    - by Adam Lassek
    I have a series of Extension methods to help with null-checking on IDataRecord objects, which I'm currently implementing like this: public static int? GetNullableInt32(this IDataRecord dr, int ordinal) { int? nullInt = null; return dr.IsDBNull(ordinal) ? nullInt : dr.GetInt32(ordinal); } public static int? GetNullableInt32(this IDataRecord dr, string fieldname) { int ordinal = dr.GetOrdinal(fieldname); return dr.GetNullableInt32(ordinal); } and so on, for each type I need to deal with. I'd like to reimplement these as a generic method, partly to reduce redundancy and partly to learn how to write generic methods in general. I've written this: public static Nullable<T> GetNullable<T>(this IDataRecord dr, int ordinal) { Nullable<T> nullValue = null; return dr.IsDBNull(ordinal) ? nullValue : (Nullable<T>) dr.GetValue(ordinal); } which works as long as T is a value type, but if T is a reference type it won't. This method would need to return either a Nullable type if T is a value type, and default(T) otherwise. How would I implement this behavior?

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  • ACCESS 2003 Excel 2003 : VBA for opening Excel file from Access and copying a pictre from excel the

    - by Justin
    So I have an excel workbook that has a nice global map of shaperange objects. With some very simple code I can change the colors, group and ungroup collections of countries into arrays, etc...and it works pretty well. However, I would like to bring this into Access. So I could copy and paste all the shapes into an access form manually, but then they become pictures and I cannot change the colors of the countries (shaperange objects) to have the map act interactively as I can in excel. So I am thinking that I know how to use excel functions from access, and how to open excel from access. Is there a way to copy an object from excel (I know the file name and the shape name that i mean to copy everytime), and bringing it back to access to paste on a form? Atypical, I know, all my Access questions are. Thanks!

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  • PHP 'instanceof' failing with class constant

    - by Nathan Loding
    I'm working on a framework that I'm trying to type as strongly as I possibly can. (I'm working within PHP and taking some of the ideas that I like from C# and trying to utilize them within this framework.) I'm creating a Collection class that is a collection of domain entities/objects. It's kinda modeled after the List<T> object in .Net. I've run into an obstacle that is preventing me from typing this class. If I have a UserCollection, it should only allow User objects into it. If I have a PostCollection, it should only allow Post objects. All Collections in this framework need to have certain basic functions, such as add, remove, iterate. I created an interface, but found that I couldn't do the following: interface ICollection { public function add($obj) } class PostCollection implements ICollection { public function add(Post $obj) {} } This broke it's compliance with the interface. But I can't have the interface strongly typed because then all Collections are of the same type. So I attempted the following: interface ICollection { public function add($obj) } abstract class Collection implements ICollection { const type = 'null'; } class PostCollection { const type = 'Post'; public function add($obj) { if(!($obj instanceof self::type)) { throw new UhOhException(); } } } When I attempt to run this code, I get syntax error, unexpected T_STRING, expecting T_VARIABLE or '$' on the instanceof statement. A little research into the issue and it looks like the root of the cause is that $obj instanceof self is valid to test against the class. It appears that PHP doesn't process the entire self::type constant statement in the expression. Adding parentheses around the self::type variable threw an error regarding an unexpected '('. An obvious workaround is to not make the type variable a constant. The expression $obj instanceof $this->type works just fine (if $type is declared as a variable, of course). I'm hoping that there's a way to avoid that, as I'd like to define the value as a constant to avoid any possible change in the variable later. Any thoughts on how I can achieve this, or have I take PHP to it's limit in this regard? Is there a way of "escaping" or encapsulating self::this so that PHP won't die when processing it?

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  • VB.net: Custom ' TODO: List on an Interface

    - by Shiftbit
    How do I add my own todo and comments list to appear on Interfaces? I want it to pop up like IDisposable does: Public Class Foo : Implements IDisposable Private disposedValue As Boolean = False ' To detect redundant calls ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If ' TODO: free your own state (unmanaged objects). ' TODO: set large fields to null. End If Me.disposedValue = True End Sub #Region " IDisposable Support " ' This code added by Visual Basic to correctly implement the disposable pattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub #End Region End Class Whenever I enter my own comments and todo list they are never autogenerated like IDisposable Interface does. I would like my own Interfaces to preserve the comments so that I can share my Interfaces with in source documentation.

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  • Get more error information from unhandled error

    - by Andrew Simpson
    I am using C# in a desktop application. I am calling a DLL written in C that I do not have the source code for. Whenever I call this DLL I get an untrapped error which I trap in an UnhandledException event/delegate. The error is : object reference not set to an instance of an object But the stack trace is empty. When I Googled this the info back was that the error was being hanlded eleswhere and then rethrown. But this can only be in the DLL I do not have the source code for. So, is there anyway I can get more info about this error? This is my code... in program.cs... AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException); static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e) { try { Exception _ex = (Exception)e.ExceptionObject; //the stact trace property is empty here.. } finally { Application.Exit(); } } My DLL... [DllImport("AutoSearchDevice.dll", EntryPoint = "Start", ExactSpelling = false, CallingConvention = CallingConvention.StdCall)] public static extern int Start(int ASD_HANDLE); An I call it like so: public static void AutoSearchStart() { try { Start(m_pASD); } catch (Exception ex) { } }

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  • Conceptual question about NSAutoreleasePools

    - by ryyst
    In my Cocoa program, wouldn't a really simple way of dealing with autoreleased objects be to just create a timer object inside the app delegate that calls the following method e.g. every 10 seconds: if (pool) { // Release & drain the current pool to free the memory. [pool release]; } // Create a new pool. pool = [[NSAutoreleasePool alloc] init]; The only problems I can imagine are: 1) If the above code runs in a separate thread, an object might get autoreleased between the release call to the old pool and the creation of the new pool - that seems highly unlikely though. 2) It's obviously not that efficient, because the pool might get released if there's nothing in it. Likewise, in the 10 second gap, many many objects might be autoreleased, causing the pool to grow a lot. Still, the above solution seems pretty suitable to small and simple projects. Why doesn't anybody use it? What's the best practice of using NSAutoreleasePools?

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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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  • Multiple SessionFactories in Windows Service with NHibernate

    - by Rob Taylor
    Hi all, I have a Webapp which connects to 2 DBs (one core, the other is a logging DB). I must now create a Windows service which will use the same business logic/Data access DLLs. However when I try to reference 2 session factories in the Service App and call the factory.GetCurrentSession() method, I get the error message "No session bound to current context". Does anyone have a suggestion about how this can be done? public class StaticSessionManager { public static readonly ISessionFactory SessionFactory; public static readonly ISessionFactory LoggingSessionFactory; static StaticSessionManager() { string fileName = System.Configuration.ConfigurationSettings.AppSettings["DefaultNHihbernateConfigFile"]; string executingPath = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase); fileName = executingPath + "\\" + fileName; SessionFactory = cfg.Configure(fileName).BuildSessionFactory(); cfg = new Configuration(); fileName = System.Configuration.ConfigurationSettings.AppSettings["LoggingNHihbernateConfigFile"]; fileName = executingPath + "\\" + fileName; LoggingSessionFactory = cfg.Configure(fileName).BuildSessionFactory(); } } The configuration file has the setting: <property name="current_session_context_class">call</property> The service sets up the factories: private ISession _session = null; private ISession _loggingSession = null; private ISessionFactory _sessionFactory = StaticSessionManager.SessionFactory; private ISessionFactory _loggingSessionFactory = StaticSessionManager.LoggingSessionFactory; ... _sessionFactory = StaticSessionManager.SessionFactory; _loggingSessionFactory = StaticSessionManager.LoggingSessionFactory; _session = _sessionFactory.OpenSession(); NHibernate.Context.CurrentSessionContext.Bind(_session); _loggingSession = _loggingSessionFactory.OpenSession(); NHibernate.Context.CurrentSessionContext.Bind(_loggingSession); So finally, I try to call the correct factory by: ISession session = StaticSessionManager.SessionFactory.GetCurrentSession(); Can anyone suggest a better way to handle this? Thanks in advance! Rob

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  • Using Core Data Concurrently and Reliably

    - by John Topley
    I'm building my first iOS app, which in theory should be pretty straightforward but I'm having difficulty making it sufficiently bulletproof for me to feel confident submitting it to the App Store. Briefly, the main screen has a table view, upon selecting a row it segues to another table view that displays information relevant for the selected row in a master-detail fashion. The underlying data is retrieved as JSON data from a web service once a day and then cached in a Core Data store. The data previous to that day is deleted to stop the SQLite database file from growing indefinitely. All data persistence operations are performed using Core Data, with an NSFetchedResultsController underpinning the detail table view. The problem I am seeing is that if you switch quickly between the master and detail screens several times whilst fresh data is being retrieved, parsed and saved, the app freezes or crashes completely. There seems to be some sort of race condition, maybe due to Core Data importing data in the background whilst the main thread is trying to perform a fetch, but I'm speculating. I've had trouble capturing any meaningful crash information, usually it's a SIGSEGV deep in the Core Data stack. The table below shows the actual order of events that happen when the detail table view controller is loaded: Main Thread Background Thread viewDidLoad Get JSON data (using AFNetworking) Create child NSManagedObjectContext (MOC) Parse JSON data Insert managed objects in child MOC Save child MOC Post import completion notification Receive import completion notification Save parent MOC Perform fetch and reload table view Delete old managed objects in child MOC Save child MOC Post deletion completion notification Receive deletion completion notification Save parent MOC Once the AFNetworking completion block is triggered when the JSON data has arrived, a nested NSManagedObjectContext is created and passed to an "importer" object that parses the JSON data and saves the objects to the Core Data store. The importer executes using the new performBlock method introduced in iOS 5: NSManagedObjectContext *child = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [child setParentContext:self.managedObjectContext]; [child performBlock:^{ // Create importer instance, passing it the child MOC... }]; The importer object observes its own MOC's NSManagedObjectContextDidSaveNotification and then posts its own notification which is observed by the detail table view controller. When this notification is posted the table view controller performs a save on its own (parent) MOC. I use the same basic pattern with a "deleter" object for deleting the old data after the new data for the day has been imported. This occurs asynchronously after the new data has been fetched by the fetched results controller and the detail table view has been reloaded. One thing I am not doing is observing any merge notifications or locking any of the managed object contexts or the persistent store coordinator. Is this something I should be doing? I'm a bit unsure how to architect this all correctly so would appreciate any advice.

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  • Visual Studio breaks, and steps, but sometimes steps out

    - by James Wilkins
    Something very odd is going on. It's been going on for some time, but I've just ignored it up to now. I have both a Silverlight and WCF service in my solution, which shares .CS file between them (one project has a link to the file, which exists in the other project). While debugging the Silverlight app, pressing the F10 key steps through code as normal, and when I get to a method call which exists in the shared file (between the projects), and Press F11, it simply skips the method instead of stepping into it (and yes, the "Just My Code" option is not checked). If I put a breakpoint in the method I'm trying to get into, it works fine (as in the debugger will break on the line), but as soon as I step (F10) it exits the method (and with F11 [step into] also). Ok, on first thought, you might think it's to do with the link, but no, it isn't. I tried removing the link and using a copy instead, but the same thing happens. And no, it's not the debug symbols, I looked into that already. The method I'm trying to step through is static, and is in a non-static partial class, in a file shared by both projects. My guess: The same types and static methods exist in the WCF and Silverlight ... would the debugger get confused?

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  • Generic InBetween Function.

    - by Luiscencio
    I am tired of writing x > min && x < max so i wawnt to write a simple function but I am not sure if I am doing it right... actually I am not cuz I get an error: bool inBetween<T>(T x, T min, T max) where T:IComparable { return (x > min && x < max); } errors: Operator '>' cannot be applied to operands of type 'T' and 'T' Operator '<' cannot be applied to operands of type 'T' and 'T' may I have a bad understanding of the where part in the function declaring note: for those who are going to tell me that I will be writing more code than before... think on readability =) any help will be appreciated EDIT deleted cuz it was resolved =) ANOTHER EDIT so after some headache I came out with this (ummm) thing following @Jay Idea of extreme readability: public static class test { public static comparision Between<T>(this T a,T b) where T : IComparable { var ttt = new comparision(); ttt.init(a); ttt.result = a.CompareTo(b) > 0; return ttt; } public static bool And<T>(this comparision state, T c) where T : IComparable { return state.a.CompareTo(c) < 0 && state.result; } public class comparision { public IComparable a; public bool result; public void init<T>(T ia) where T : IComparable { a = ia; } } } now you can compare anything with extreme readability =) what do you think.. I am no performance guru so any tweaks are welcome

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  • what is this 'content_type' mean..

    - by zjm1126
    content_type = ContentType.objects.get_for_model(Map) maps = maps.extra(select=SortedDict([ ('member_count', MEMBER_COUNT_SQL), ('topic_count', TOPIC_COUNT_SQL), ]), select_params=(content_type.id,)) and the ContentType is: class ContentType(models.Model): name = models.CharField(max_length=100) app_label = models.CharField(max_length=100) model = models.CharField(_('python model class name'), max_length=100) objects = ContentTypeManager() class Meta: verbose_name = _('content type') verbose_name_plural = _('content types') db_table = 'django_content_type' ordering = ('name',) unique_together = (('app_label', 'model'),) def __unicode__(self): return self.name def model_class(self): "Returns the Python model class for this type of content." from django.db import models return models.get_model(self.app_label, self.model) def get_object_for_this_type(self, **kwargs): """ Returns an object of this type for the keyword arguments given. Basically, this is a proxy around this object_type's get_object() model method. The ObjectNotExist exception, if thrown, will not be caught, so code that calls this method should catch it. """ return self.model_class()._default_manager.using(self._state.db).get(**kwargs) def natural_key(self): return (self.app_label, self.model) i want to know: what is the 'content_type' used for ??

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  • Persisting a single UISearchBar instance across 4 separate UITableViews

    - by Jacob Relkin
    Hi fellas, I'm in the midst of an iPhone app that needs to have 4 separate UITableView objects sharing access to one UISearchBar in the first section and first row of the aforementioned UITableView objects. I have tried to offset the UITableView's frame by 44 pixels, then adding the search bar as a subview of my UIViewController's view. That works, but I cannot use the table index to scroll up to the search bar, since it is not a cell in the tableview. I need to have the search bar in the table view itself. My goal is to have the same UISearchBar in the first section of multiple tableviews. Thanks so much.

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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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  • Problem in setting backgound color to my TreeCellRenderer

    - by Sunil Kumar Sahoo
    Hi I have cretaed my own renderer. I want the back ground should be blue. I have set background color as blue also. But I donot know what is tha problem that the background color of my renderer always seems to be white. I have post the code. please help where I am wrong so that the background color becomes white. class CheckTreeCellRenderer extends JPanel implements TreeCellRenderer { private CheckTreeSelectionModel selectionModel; private MyRenderer delegate; private TristateCheckBox checkBox = new TristateCheckBox("", null, true); public static final State NOT_SELECTED = new State(); public static final State SELECTED = new State(); public static final State DONT_CARE = new State(); public CheckTreeCellRenderer(MyRenderer delegate, CheckTreeSelectionModel selectionModel) { this.delegate = delegate; this.selectionModel = selectionModel; setLayout(new BorderLayout()); setOpaque(true); setBackground(new Color(207, 219, 234)); checkBox.setState(Boolean.TRUE); checkBox.setOpaque(true); checkBox.setBackground(new Color(207, 219, 234)); } public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) { Component renderer = delegate.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus); TreePath path = tree.getPathForRow(row); if (path != null) { if (selectionModel.isPathSelected(path, true)) { checkBox.setState(Boolean.TRUE); } else { checkBox.setState(selectionModel.isPartiallySelected(path) ? null : Boolean.FALSE); } } renderer.setBackground(new Color(207, 219, 234)); tree.setOpaque(true); tree.setBackground(new Color(207, 219, 234)); this.setOpaque(true); this.setBackground(new Color(207, 219, 234)); add(checkBox, BorderLayout.WEST); add(renderer, BorderLayout.CENTER); return this; } }

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  • Choosing a design pattern for a class that might change it's internal attributes

    - by the_drow
    I have a class that holds arbitrary state and it's defined like this: class AbstractFoo { }; template <class StatePolicy> class Foo : public StatePolicy, public AbstractFoo { }; The state policy contains only protected attributes that represent the state. The state might be the same for multiple behaviors and they can be replaced at runtime. All Foo objects have the same interface to abstract the state itself and to enable storing Foo objects in containers. I would like to find the least verbose and the most maintainable way to express this.

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  • objective C convert NSString to unsigned

    - by user1501354
    I have changed my question. I want to convert an NSString to an unsigned int. Why? Because I want to do parallel payment in PayPal. Below I have given my coding in which I want to convert the NSString to an unsigned int. My query is: //optional, set shippingEnabled to TRUE if you want to display shipping //options to the user, default: TRUE [PayPal getPayPalInst].shippingEnabled = TRUE; //optional, set dynamicAmountUpdateEnabled to TRUE if you want to compute //shipping and tax based on the user's address choice, default: FALSE [PayPal getPayPalInst].dynamicAmountUpdateEnabled = TRUE; //optional, choose who pays the fee, default: FEEPAYER_EACHRECEIVER [PayPal getPayPalInst].feePayer = FEEPAYER_EACHRECEIVER; //for a payment with multiple recipients, use a PayPalAdvancedPayment object PayPalAdvancedPayment *payment = [[PayPalAdvancedPayment alloc] init]; payment.paymentCurrency = @"USD"; // A payment note applied to all recipients. payment.memo = @"A Note applied to all recipients"; //receiverPaymentDetails is a list of PPReceiverPaymentDetails objects payment.receiverPaymentDetails = [NSMutableArray array]; NSArray *emailArray = [NSArray arrayWithObjects:@"[email protected]",@"[email protected]", nil]; for (int i = 1; i <= 2; i++) { PayPalReceiverPaymentDetails *details = [[PayPalReceiverPaymentDetails alloc] init]; // Customize the payment notes for one of the three recipient. if (i == 2) { details.description = [NSString stringWithFormat:@"Component %d", i]; } details.recipient = [NSString stringWithFormat:@"%@",[emailArray objectAtIndex:i-1]]; unsigned order; if (i==1) { order = [[feeArray objectAtIndex:0] unsignedIntValue]; } if (i==2) { order = [[amountArray objectAtIndex:0] unsignedIntValue]; } //subtotal of all items for this recipient, without tax and shipping details.subTotal = [NSDecimalNumber decimalNumberWithMantissa:order exponent:-4 isNegative:FALSE]; //invoiceData is a PayPalInvoiceData object which contains tax, shipping, and a list of PayPalInvoiceItem objects details.invoiceData = [[PayPalInvoiceData alloc] init]; //invoiceItems is a list of PayPalInvoiceItem objects //NOTE: sum of totalPrice for all items must equal details.subTotal //NOTE: example only shows a single item, but you can have more than one details.invoiceData.invoiceItems = [NSMutableArray array]; PayPalInvoiceItem *item = [[PayPalInvoiceItem alloc] init]; item.totalPrice = details.subTotal; [details.invoiceData.invoiceItems addObject:item]; [payment.receiverPaymentDetails addObject:details]; } [[PayPal getPayPalInst] advancedCheckoutWithPayment:payment]; Can anybody tell me how to do this conversion? Thanks and regards in advance.

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  • Extracting Information from Images

    - by Khorkrak
    What are some fast and somewhat reliable ways to extract information about images? I've been tinkering with openCV and this seems so far to be the best route plus it has Python bindings. So to be more specific I'd like to determine what I can about what's in an image. So for example the haar face detection and full body detection classifiers are great - now I can tell that most likely there are faces and / or people in the image as well as about how many. okay - what else - how about whether there are any buildings and if so what do they seem to be - huts, office buildings etc? Is there sky visible, grass, trees and so forth. From what I've read about training classifiers to detect objects, it seems like a rather laborious process 10,000 or so wrong images and 5,000 or so correct samples to train a classifier. I'm hoping that there are some decent ones around already instead of having to do this all myself for a bunch of different objects - or is there some other way to go about this sort of thing?

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  • Setting up a "to-many" relationship value dependency for a transient Core Data attribute

    - by Greg Combs
    I've got a relatively complicated Core Data relationship structure and I'm trying to figure out how to set up value dependencies (or observations) across various to-many relationships. Let me start out with some basic info. I've got a classroom with students, assignments, and grades (students X assignments). For simplicity's sake, we don't really have to focus much on the assignments yet. StudentObj <--->> ScoreObj <<---> AssignmentObj Each ScoreObj has a to-one relation with the StudentObj and the AssignmentObj. ScoreObj has real attributes for the numerical grade, the turnInDate, and notes. AssignmentObj.scores is the set of Score objects for that assignment (N = all students). AssignmentObj has real attributes for name, dueDate, curveFunction, gradeWeight, and maxPoints. StudentObj.scores is the set of Score objects for that student (N = all assignments). StudentObj also has real attributes like name, studentID, email, etc. StudentObj has a transient (calculated, not stored) attribute called gradeTotal. This last item, gradeTotal, is the real pickle. it calculates the student's overall semester grade using the scores (ScoreObj) from all their assignments, their associated assignment gradeWeights, curves, and maxPoints, and various other things. This gradeTotal value is displayed in a table column, along with all the students and their individual assignment grades. Determining the value of gradeTotal is a relatively expensive operation, particularly with a large class, therefore I want to run it only when necessary. For simplicity's sake, I'm not storing that gradeTotal value in the core data model. I don't mind caching it somewhere, but I'm having a bitch of a time determining where and how to best update that cache. I need to run that calculation for each student whenever any value changes that affects their gradeTotal. If this were a simple to-one relationship, I know I could use something like keyPathsForValuesAffectingGradeTotal ... but it's more like a many-to-one-to-many relationship. Does anyone know of an elegant (and KVC correct) solution? I guess I could tear through all those score and assignment objects and tell them to register their students as observers. But this seems like a blunt force approach.

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  • Mocking imported modules in Python

    - by Evgenyt
    I'm trying to implement unit tests for function that uses imported external objects. For example helpers.py is: import os import pylons def some_func(arg): ... var1 = os.path.exist(...) var2 = os.path.getmtime(...) var3 = pylons.request.environ['HTTP_HOST'] ... So when I'm creating unit test for it I do some mocking (minimock in my case) and replacing references to pylons.request and os.path: import helpers def test_some_func(): helpers.pylons.request = minimock.Mock("pylons.request") helpers.pylons.request.environ = { 'HTTP_HOST': "localhost" } helpers.os.path = minimock.Mock(....) ... some_func(...) # assert ... This does not look good for me. Is there any other better way or strategy to substitute imported function/objects in Python?

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  • Can a variable bu used 2nd time after releasing it?

    - by Jakub
    Hello, I try to understand the memory management in ObjectiveC and still some things are a misery for me. I've got an instance variable: NSMutableArray *postResultsArray; when a button is clicked in the UI I create new array: self.postResultsArray = [NSMutableArray array]; then I add some objects to the array and when the whole operation is done I would like to release the array: [self.postResultsArray release]; (I assume that all the objects stoed in the array will be released along with the array). The problem appears when I click the button again and in the code I want to create the array again with: self.postResultsArray = [NSMutableArray array]; I get: [CFArray release]: message sent to deallocated instance 0x3d9e390 Can't I initialize the same instance variable for the second time? or maybe I should not release it? and if so, why? Thanks!

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  • Help With LINQ: Mixed Joins and Specifying Default Values

    - by Corey O.
    I am trying to figure out how to do a mixed-join in LINQ with specific access to 2 LINQ objects. Here is an example of how the actual TSQL query might look: SELECT * FROM [User] AS [a] INNER JOIN [GroupUser] AS [b] ON [a].[UserID] = [b].[UserID] INNER JOIN [Group] AS [c] ON [b].[GroupID] = [c].[GroupID] LEFT JOIN [GroupEntries] AS [d] ON [a].[GroupID] = [d].[GroupID] WHERE [a].[UserID] = @UserID At the end, basically what I would like is an enumerable object full of GroupEntry objects. What am interested is the last two tables/objects in this query. I will be displaying Groups as a group header, and all of the Entries underneath their group heading. If there are no entries for a group, I still want to see that group as a header without any entries. Here's what I have so far: So from that I'd like to make a function: public void DisplayEntriesByUser(int user_id) { MyDataContext db = new MyDataContext(); IEnumberable<GroupEntries> entries = ( from user in db.Users where user.UserID == user_id join group_user in db.GroupUsers on user.UserID = group_user.UserID into a from join1 in a join group in db.Groups on join1.GroupID equals group.GroupID into b from join2 in b join entry in db.Entries.DefaultIfEmpty() on join2.GroupID equals entry.GroupID select entry ); Group last_group_id = 0; foreach(GroupEntry entry in entries) { if (last_group_id == 0 || entry.GroupID != last_group_id) { last_group_id = entry.GroupID; System.Console.WriteLine("---{0}---", entry.Group.GroupName.ToString().ToUpper()); } if (entry.EntryID) { System.Console.WriteLine(" {0}: {1}", entry.Title, entry.Text); } } } The example above does not work quite as expected. There are 2 problems that I have not been able to solve: I still seem to be getting an INNER JOIN instead of a LEFT JOIN on the last join. I am not getting any empty results, so groups without entries do not appear. I need to figure out a way so that I can fill in the default values for blank sets of entries. That is, if there is a group without an entry, I would like to have a mostly blank entry returned, except that I'd want the EntryID to be null or 0, the GroupID to be that of of the empty group that it represents, and I'd need a handle on the entry.Group object (i.e. it's parent, empty Group object). Any help on this would be greatly appreciated. Note: Table names and real-world representation were derived purely for this example, but their relations simplify what I'm trying to do.

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  • What is the algorithm used by the memberwise equality test in .NET structs?

    - by Damian Powell
    What is the algorithm used by the memberwise equality test in .NET structs? I would like to know this so that I can use it as the basis for my own algorithm. I am trying to write a recursive memberwise equality test for arbitrary objects (in C#) for testing the logical equality of DTOs. This is considerably easier if the DTOs are structs (since ValueType.Equals does mostly the right thing) but that is not always appropriate. I would also like to override comparison of any IEnumerable objects (but not strings!) so that their contents are compared rather than their properties. This has proven to be harder than I would expect. Any hints will be greatly appreciated. I'll accept the answer that proves most useful or supplies a link to the most useful information. Thanks.

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