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• Can Haskell's monads be thought of as using and returning a hidden state parameter?

  - by AJM

  I don't understand the exact algebra and theory behind Haskell's monads. However, when I think about functional programming in general I get the impression that state would be modelled by taking an initial state and generating a copy of it to represent the next state. This is like when one list is appended to another; neither list gets modified, but a third list is created and returned. Is it therefore valid to think of monadic operations as implicitly taking an initial state object as a parameter and implicitly returning a final state object? These state objects would be hidden so that the programmer doesn't have to worry about them and to control how they gets accessed. So, the programmer would not try to copy the object representing the IO stream as it was ten minutes ago. In other words, if we have this code: main = do putStrLn "Enter your name:" name <- getLine putStrLn ( "Hello " ++ name ) ...is it OK to think of the IO monad and the "do" syntax as representing this style of code? putStrLn :: IOState -> String -> IOState getLine :: IOState -> (IOState, String) main :: IOState -> IOState -- main returns an IOState we can call "state3" main state0 = putStrLn state2 ("Hello " ++ name) where (state2, name) = getLine state1 state1 = putStrLn state0 "Enter your name:"

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• Howw to add new value with generic Repository if there are foreign keys (EF-4)?

  - by Phsika

  i try to write a kind of generic repository to add method. Everything is ok to add but I have table which is related with two tables with FOREIGN KEY.But Not working because of foreign key public class DomainRepository<TModel> : IDomainRepository<TModel> where TModel : class { #region IDomainRepository<T> Members private ObjectContext _context; private IObjectSet<TModel> _objectSet; public DomainRepository() { } public DomainRepository(ObjectContext context) { _context = context; _objectSet = _context.CreateObjectSet<TModel>(); } //do something..... public TModel Add<TModel>(TModel entity) where TModel : IEntityWithKey { EntityKey key; object originalItem; key = _context.CreateEntityKey(entity.GetType().Name, entity); _context.AddObject(key.EntitySetName, entity); _context.SaveChanges(); return entity; } //do something..... } Calling REPOSITORY: //insert-update-delete public partial class AddtoTables { public table3 Add(int TaskId, int RefAircraftsId) { using (DomainRepository<table3> repTask = new DomainRepository<table3>(new TaskEntities())) { return repTask.Add<table3>(new table3() { TaskId = TaskId, TaskRefAircraftsID = RefAircraftsId }); } } } How to add a new value if this table includes foreign key relation

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• Random number generation in MVC applications

  - by SlimShaggy

  What is the correct way of generating random numbers in an ASP.NET MVC application if I need exactly one number per request? According to MSDN, in order to get randomness of sufficient quality, it is necessary to generate multiple numbers using a single System.Random object, created once. Since a new instance of a controller class is created for each request in MVC, I cannot use a private field initialized in the controller's constructor for the Random object. So in what part of the MVC app should I create and store the Random object? Currently I store it in a static field of the controller class and lazily initialize it in the action method that uses it: public class HomeController : Controller { ... private static Random random; ... public ActionResult Download() { ... if (random == null) random = new Random(); ... } } Since the "random" field can be accessed by multiple instances of the controller class, is it possible for its value to become corrupted if two instances attempt to initialize it simultaneously? And one more question: I know that the lifetime of statics is the lifetime of the application, but in case of an MVC app what is it? Is it from IIS startup till IIS shutdown?

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• highlight listview items android

  - by user1752939

  I have listview with custom base adapter. When I populate the list I have to check a boolean in the object I'm populating the listview and if it is true to change the background color of that row. public View getView(int position, View convertView, ViewGroup parent) { LoginsList entry = listOfLoginsLists.get(position); if (convertView == null) { LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); convertView = inflater.inflate(R.layout.lists_row, null); } TextView ListName = (TextView) convertView.findViewById(R.id.tvListName); ListName.setText(entry.getListName()); TextView ListDescription = (TextView) convertView.findViewById(R.id.tvListDescription); ListDescription.setText(entry.getListDescription()); Button Send = (Button) convertView.findViewById(R.id.bSend); Send.setOnClickListener(this); Send.setTag(entry); RelativeLayout RelLayout = (RelativeLayout) convertView.findViewById(R.id.layoutListsRow); RelLayout.setFocusableInTouchMode(false); RelLayout.setFocusable(false); RelLayout.setOnClickListener(this); RelLayout.setTag(entry); if (entry.isSent()) { RelLayout.setBackgroundColor(Color.parseColor("#4400FF00")); } return convertView; } But this code doesn't work right. When I scroll the list view the rows colors get messed up.

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• Python: why can't descriptors be instance variables?

  - by Continuation

  Say I define this descriptor: class MyDescriptor(object): def __get__(self, instance, owner): return self._value def __set__(self, instance, value): self._value = value def __delete__(self, instance): del(self._value) And I use it in this: class MyClass1(object): value = MyDescriptor() >>> m1 = MyClass1() >>> m1.value = 1 >>> m2 = MyClass1() >>> m2.value = 2 >>> m1.value 2 So value is a class attribute and is shared by all instances. Now if I define this: class MyClass2(object) value = 1 >>> y1 = MyClass2() >>> y1.value=1 >>> y2 = MyClass2() >>> y2.value=2 >>> y1.value 1 In this case value is an instance attribute and is not shared by the instances. Why is it that when value is a descriptor it can only be a class attribute, but when value is a simple integer it becomes an instance attribute?

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• Pattern for version-specific implementations of a Java class

  - by Mike Monkiewicz

  So here's my conundrum. I am programming a tool that needs to work on old versions of our application. I have the code to the application, but can not alter any of the classes. To pull information out of our database, I have a DTO of sorts that is populated by Hibernate. It consumes a data object for version 1.0 of our app, cleverly named DataObject. Below is the DTO class. public class MyDTO { private MyWrapperClass wrapper; public MyDTO(DataObject data) { wrapper = new MyWrapperClass(data); } } The DTO is instantiated through a Hibernate query as follows: select new com.foo.bar.MyDTO(t1.data) from mytable t1 Now, a little logic is needed on top of the data object, so I made a wrapper class for it. Note the DTO stores an instance of the wrapper class, not the original data object. public class MyWrapperClass { private DataObject data; public MyWrapperClass(DataObject data) { this.data = data; } public String doSomethingImportant() { ... version-specific logic ... } } This works well until I need to work on version 2.0 of our application. Now DataObject in the two versions are very similar, but not the same. This resulted in different sub classes of MyWrapperClass, which implement their own version-specific doSomethingImportant(). Still doing okay. But how does myDTO instantiate the appropriate version-specific MyWrapperClass? Hibernate is in turn instantiating MyDTO, so it's not like I can @Autowire a dependency in Spring. I would love to reuse MyDTO (and my dozens of other DTOs) for both versions of the tool, without having to duplicate the class. Don't repeat yourself, and all that. I'm sure there's a very simple pattern I'm missing that would help this. Any suggestions?

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• C Programming. How to deep copy a struct?

  - by user69514

  I have the following two structs where "child struct" has a "rusage struct" as an element. Then I create two structs of type "child" let's call them childA and childB How do I copy just the rusage struct from childA to childB? typedef struct{ int numb; char *name; pid_t pid; long userT; long systemT; struct rusage usage; }child; typedef struct{ struct timeval ru_utime; /* user time used */ struct timeval ru_stime; /* system time used */ long ru_maxrss; /* maximum resident set size */ long ru_ixrss; /* integral shared memory size */ long ru_idrss; /* integral unshared data size */ long ru_isrss; /* integral unshared stack size */ long ru_minflt; /* page reclaims */ long ru_majflt; /* page faults */ long ru_nswap; /* swaps */ long ru_inblock; /* block input operations */ long ru_oublock; /* block output operations */ long ru_msgsnd; /* messages sent */ long ru_msgrcv; /* messages received */ long ru_nsignals; /* signals received */ long ru_nvcsw; /* voluntary context switches */ long ru_nivcsw; /* involuntary context switches */ }rusage; I did the following, but I guess it copies the memory location, because if I changed the value of usage in childA, it also changes in childB. memcpy(&childA,&childB, sizeof(rusage)); I know that gives childB all the values from childA. I have already taken care of the others fields in childB, I just need to be able to copy the rusage struct called usage that resides in the "child" struct.

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• friend declaration in C++

  - by Happy Mittal

  In Thinking in C++ by Bruce eckel, there is an example given regarding friend functions as // Declaration (incomplete type specification): struct X; struct Y { void f(X*); }; struct X { // Definition private: int i; public: friend void Y::f(X*); // Struct member friend }; void Y::f(X* x) { x->i = 47; } Now he explained this: Notice that Y::f(X*) takes the address of an X object. This is critical because the compiler always knows how to pass an address, which is of a fixed size regardless of the object being passed, even if it doesn’t have full information about the size of the type. If you try to pass the whole object, however, the compiler must see the entire structure definition of X, to know the size and how to pass it, before it allows you to declare a function such as Y::g(X). But when I tried void f(X); as declaration in struct Y, it shows no error. Please explain why?

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• Javascript private member on prototype...

  - by Wilq32

  Well I tried to figure out is this possible in any way. Here is code: a=function(text) { var b=text; if (!arguments.callee.prototype.get) arguments.callee.prototype.get=function() { return b; } else alert('already created!'); } var c=new a("test"); // creates prototype instance of getter var d=new a("ojoj"); // alerts already created alert(c.get()) // alerts test alert(d.get()) // alerts test from context of creating prototype function :( As you see I tried to create prototype getter. For what? Well if you write something like this: a=function(text) { var b=text; this.getText=function(){ return b} } ... everything should be fine.. but in fact every time I create object - i create getText function that uses memory. I would like to have one prototypical function lying in memory that would do the same... Any ideas? EDIT: I tried solution given by Christoph, and it seems that its only known solution for now. It need to remember id information to retrieve value from context, but whole idea is nice for me :) Id is only one thing to remember, everything else can be stored once in memory. In fact you could store a lot of private members this way, and use anytime only one id. Actually this is satisfying me :) (unless someone got better idea). someFunc = function() { var store = new Array(); var guid=0; var someFunc = function(text) { this.__guid=guid; store[guid++]=text; } someFunc.prototype.getValue=function() { return store[this.__guid]; } return someFunc; }() a=new someFunc("test"); b=new someFunc("test2"); alert(a.getValue()); alert(b.getValue());

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• Java and Jasper

  - by bhargava

  Hey Guys, I have integrated Jasper Reports on my netbeans platform and i am able to generate reports using the following code. Map<String, Object> params = new HashMap<String, Object>(); Connection conn = DriverManager.getConnection("databaseUrl", "userid","password"); JasperReport jasperReport = JasperCompileManager.compileReport(reportSource); JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, params, conn); JasperExportManager.exportReportToHtmlFile(jasperPrint, reportDest); JasperViewer.viewReport(jasperPrint); This stuff works perfect. But not i am trying to integrate Jasper with GWT.I have my server as glass fish server. I am getting the Connection object using the followind code. public static Connection getConnection() { try { String JNDI = "JNDI name"; InitialContext initCtx = new InitialContext(); javax.sql.DataSource ds = (javax.sql.DataSource) initCtx.lookup(JNDI); Connection conn = (Connection) ds.getConnection(); return conn; } catch (Exception ex) { ex.printStackTrace(); } return null; } and then Map params = new HashMap(); JasperReport jasperReport = JasperCompileManager.compileReport(reportSource); JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, params, getConnection()); JasperExportManager.exportReportToHtmlFile(jasperPrint, reportDest); JasperViewer.viewReport(jasperPrint); but i always get Error.I am implementing this on Server.I am having RPC calls to get this method to work when a button is clicked. Can you please help me how to work on this.(That is to integrate Jasper reports with GWT). I would highly appreciate any explanation with some code as i am just a beginner. Thanks

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• Why aren't variables declared in "try" in scope in "catch" or "finally"?

  - by Jon Schneider

  In C# and in Java (and possibly other languages as well), variables declared in a "try" block are not in scope in the corresponding "catch" or "finally" blocks. For example, the following code does not compile: try { String s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } In this code, a compile-time error occurs on the reference to s in the catch block, because s is only in scope in the try block. (In Java, the compile error is "s cannot be resolved"; in C#, it's "The name 's' does not exist in the current context".) The general solution to this issue seems to be to instead declare variables just before the try block, instead of within the try block: String s; try { s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } However, at least to me, (1) this feels like a clunky solution, and (2) it results in the variables having a larger scope than the programmer intended (the entire remainder of the method, instead of only in the context of the try-catch-finally). My question is, what were/are the rationale(s) behind this language design decision (in Java, in C#, and/or in any other applicable languages)?

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• Run code before class instanciation in ActionScript 3

  - by soow.fr

  I need to run code in a class declaration before its instanciation. This would be especially useful to automatically register classes in a factory. See: // Main.as public class Main extends Sprite { public function Main() : void { var o : Object = Factory.make(42); } } // Factory.as public class Factory { private static var _factory : Array = new Array(); public static function registerClass(id : uint, c : Class) : void { _factory[id] = function () : Object { return new c(); }; } public static function make(id : uint) : Object { return _factory[id](); } } // Foo.as public class Foo { // Run this code before instanciating Foo! Factory.registerClass(42, Foo); } AFAIK, the JIT machine for the ActionScript language won't let me do that since no reference to Foo is made in the Main method. The Foo class being generated, I can't (and don't want to) register the classes in Main: I'd like to register all the exported classes in a specific package (or library). Ideally, this would be done through package introspection, which doesn't exist in ActionScript 3. Do you know any fix (or other solution) to my design issue?

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• Why use Intent.URI_INTENT_SCHEME

  - by hks

  while reading Android docs about Widgets I stumbled upon this piece of code whose purpose is to launch a service for retrieving a factory for StackView items. // Set up the intent that starts the StackViewService, which will // provide the views for this collection. Intent intent = new Intent(context, StackWidgetService.class); // Add the app widget ID to the intent extras. intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetIds[i]); intent.setData(Uri.parse(intent.toUri(Intent.URI_INTENT_SCHEME))); // Instantiate the RemoteViews object for the App Widget layout. RemoteViews rv = new RemoteViews(context.getPackageName(), R.layout.widget_layout); // Set up the RemoteViews object to use a RemoteViews adapter. // This adapter connects // to a RemoteViewsService through the specified intent. // This is how you populate the data. rv.setRemoteAdapter(appWidgetIds[i], R.id.stack_view, intent); You can find it here I have a problem understanding why do you need to call intent.setData(Uri.parse(intent.toUri(Intent.URI_INTENT_SCHEME))); I understand that it gives URI a prefix intent://, but is it necessary here?

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• Constructor and Destructors in C++ work?

  - by Jack

  I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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• Problem with moving a winform using C#

  - by karthik

  My form doesn't have a title bar, so I am implementing the code to drag the entire form around the screen. I am using the below code to do it, which works fine. I have two panels in my form, PanelA and PanelB. During the startup I show PanelA where the dragging works perfectly. Later when the user clicks the button in PanelA, I need to make PanelA invisible and show PanelB However, the dragging does not work when PanelB is shown. What's the problem here? private void SerialPortScanner_MouseUp(object sender, MouseEventArgs e) { this.drag = false; } private void SerialPortScanner_MouseDown(object sender, MouseEventArgs e) { this.drag = true; this.start_point = new Point(e.X, e.Y); } private void SerialPortScanner_MouseMove(object sender, MouseEventArgs e) { if (this.drag) { Point p1 = new Point(e.X, e.Y); Point p2 = this.PointToScreen(p1); Point p3 = new Point(p2.X - this.start_point.X, p2.Y - this.start_point.Y); this.Location = p3; } }

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• Storing large numbers of varying size objects on disk

  - by Foredecker

  I need to develop a system for storing large numbers (10's to 100's of thousands) of objects. Each object is email-like - there is a main text body, and several ancillary text fields of limited size. A body will be from a few bytes, to several KB in size. Each item will have a single unique ID (probably a GUID) that identifies it. The store will only be written to when an object is added to it. It will be read often. Deletions will be rare. The data is almost all human readable text so it will be readily compressible. A system that lets me issue the I/Os and mange the memory and caching would be ideal. I'm going to keep the indexes in memory, using it to map indexes to the single (and primary) key for the objects. Once I have the key, then I'll load it from disk, or the cache. The data management system needs to be part of my application - I do not want to depend on OS services. Or separately installed packages. Native (C++) would be best, but a manged (C#) thing would be ok. I believe that a database is an obvious choice, but this needs to be super-fast for look up and loading into memory of an object. I am not experienced with data base tech and I'm concerned that general relational systems will not handle all this variable sized data efficiently. (Note, this has nothing to do with my job - its a personal project.) In your experience, what are the viable alternatives to a traditional relational DB? Or would a DB work well for this?

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• List of Objects to be used on ascx view with Inherits data already loaded MVC...

  - by user54197

  I have an object list being loded from a database to a drop down list. The Model loads the data to the Controller. The aspx view includes an ascx view. The ascx view already inherits data from another Project. I cannot set my List object in the ascx page. Can this be done? Model ... string List = dr["example"].ToString().Trim(); int indicator = dr["ex"].ToString().Trim(); LossCauseList.Add(new LossCauses(indicator, List)); ... Controller LossCauses test = new LossCauses(); test.GetLossCauses(LossType); TempData["Select"] = test.LossCauseList; return View(myData); Partial View ... <select id="SelectedProperty"> <% List<string> selectProperty = new List<string>(); selectProperty = TempData["Select"] as List<string>; foreach(var item in selectProperty) { %> <option><%=item.ToString() %></option> <% } %> </select> ... Partial view's List should be an actual LossCauses object. HELP!!!

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• Binary serialization and deserialization without creating files (via strings)

  - by the_V

  Hi, I'm trying to create a class that will contain functions for serializing/deserializing objects to/from string. That's what it looks like now: public class BinarySerialization { public static string SerializeObject(object o) { string result = ""; if ((o.GetType().Attributes & TypeAttributes.Serializable) == TypeAttributes.Serializable) { BinaryFormatter f = new BinaryFormatter(); using (MemoryStream str = new MemoryStream()) { f.Serialize(str, o); str.Position = 0; StreamReader reader = new StreamReader(str); result = reader.ReadToEnd(); } } return result; } public static object DeserializeObject(string str) { object result = null; byte[] bytes = System.Text.Encoding.ASCII.GetBytes(str); using (MemoryStream stream = new MemoryStream(bytes)) { BinaryFormatter bf = new BinaryFormatter(); result = bf.Deserialize(stream); } return result; } } SerializeObject method works well, but DeserializeObject does not. I always get an exception with message "End of Stream encountered before parsing was completed". What may be wrong here?

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• Laravel4: Checking many-to-many relationship attribute even when it does not exist

  - by Simo A.

  This is my first time with Laravel and also Stackoverflow... I am developing a simple course management system. The main objects are User and Course, with a many-to-many relationship between them. The pivot table has an additional attribute, participant_role, which defines whether the user is a student or an instructor within that particular course. class Course extends Eloquent { public function users() { return $this->belongsToMany('User')->withPivot('participant_role')->withTimestamps(); } } However, there is an additional role, system admin, which can be defined on the User object. And this brings me mucho headache. In my blade view I have the following: @if ($course->pivot->participant_role == 'instructor') { // do something here... } This works fine when the user has been assigned to that particular $course and there is an entry for this user-course combination in the pivot table. However, the problem is the system administrator, who also should be able to access course details. The if-clause above gives Trying to get property of non-object error, apparently because there is no entry in the pivot table for system administrator (as the role is defined within the User object). I could probably solve the problem by using some off-the-shelf bundle for handling role-based permissions. Or I could (but don't want to) do something like this with two internal if-clauses: if (!empty($course->pivot)) { if ($course->pivot->participant_role == 'instructor') { // do something... } } Other options (suggested in partially similar entries in Stackoverflow) would include 1) reading all the pivot table entries to an array, and use in_array to check if a role exists, or even 2) SQL left join to do this on database level. However, ultimately I am looking for a compact one-line solution? Can I do anything similar to this, which unfortunately does not seem to work? if (! empty ($course->pivot->participant_role == 'instructor') ) { // do something... } The shorter the answer, the better :-). Thanks a lot!

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• View isn't scrolling back down after I dismiss the keyboard

  - by fmi

  I have a Tab Bar app. One of the views has a UITextView that is hidden by the keyboard when touched. I've set the view to scroll to account for the keyboard but it the view doesn't always return to it's original position after I dismiss the keyboard. Here is my code: //Scroll the view for keyboard - (void)viewWillAppear:(BOOL)animated { void (^keyBoardWillShow) (NSNotification *)= ^(NSNotification * notif) { NSDictionary* info = [notif userInfo]; NSValue* aValue = [info objectForKey:UIKeyboardFrameEndUserInfoKey]; CGSize keyboardSize = [aValue CGRectValue].size; float bottomPoint = (additionalView.frame.origin.y + additionalView.frame.size.height + 10); scrollAmount = keyboardSize.height - (self.view.frame.size.height - bottomPoint); if (scrollAmount > 0) { moveViewUp =YES; [self scrollTheView:YES]; } else moveViewUp = NO; }; [[NSNotificationCenter defaultCenter] addObserverForName:UIKeyboardWillShowNotification object:self.view.window queue:nil usingBlock:keyBoardWillShow]; void (^keyBoardWillHide) (NSNotification *)= ^(NSNotification * notif) { if (moveViewUp) [self scrollTheView:NO]; }; [[NSNotificationCenter defaultCenter] addObserverForName:UIKeyboardWillHideNotification object:self.view.window queue:nil usingBlock:keyBoardWillHide]; [super viewWillAppear:animated]; } - (void)viewWillDisappear:(BOOL)animated { [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil]; [super viewWillDisappear:animated]; } (void)scrollTheView:(BOOL)movedUp { [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.3]; CGRect rect = self.view.frame; if (movedUp){ rect.origin.y -= scrollAmount; } else { rect.origin.y += scrollAmount; } self.view.frame = rect; [UIView commitAnimations]; }

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• c# How to find if two objects are equal

  - by Simon G

  Hi, I'm needing to know the best way to compare two objects and to find out if there equal. I'm overriding both GethashCode and Equals. So a basic class looks like: public class Test { public int Value { get; set; } public string String1 { get; set; } public string String2 { get; set; } public override int GetHashCode() { return Value ^ String1.GetHashCode() ^ String2.GetHashCode(); } public override bool Equals( object obj ) { return GetHashCode() == obj.GetHashCode(); } } So for testing purposes I created two objects: Test t = new Test() { Value = 1, String1 ="One", String2 = "One" }; Test t2 = new Test() { Value = 1, String1 = "Two", String2 = "Two" }; bool areEqual = t.Equals( t2 ); In testing this areEqual returns true event though both objects are different. I realise this is because String1 and String2 are the same value in each object and thus cancels each other out when hashing. Is there a better way off hashing object that the method I have that will resolve my issue?

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• Have something loaded only when JList item is visibile

  - by elvencode

  Hello, i'm implementing a Jlist populated with a lot of elements. Each element corresponds to a image so i'd like to show a resized preview of them inside each row of the list. I've implemented a custom ImageCellRenderer extending the Jlabel and on getListCellRendererComponent i create the thumbnail if there'snt any for that element. Each row corresponds to a Page class where i store the path of the image and the icon applied to the JLabel. Each Page object is put inside a DefaultListModel to populate the JList. The render code is something like this: public Component getListCellRendererComponent( JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) { Page page = (Page) value; if (page.getImgIcon() == null) { System.out.println(String.format("Creating thumbnail of %s", page.getImgFilename())); ImageIcon icon = new ImageIcon(page.getImgFilename()); int thumb_width = icon.getIconWidth() > icon.getIconHeight() ? 128 : ((icon.getIconWidth() * 128) / icon.getIconHeight()); int thumb_height = icon.getIconHeight() > icon.getIconWidth() ? 128 : ((icon.getIconHeight() * 128) / icon.getIconWidth()); icon.setImage(getScaledImage(icon.getImage(), thumb_width, thumb_height)); page.setImgIcon(icon); } setIcon(page.getImgIcon()); } I was thinking that only a certain item is visibile in the List the cell renderer is called but i'm seeing that all the thumnails are created when i add the Page object to the list model. I've tried to load the items and after set the model in the JList or set the model first and after starting appending the items but the results are the same. Is there any way to load the data only when necessary or do i need to create a custom control like a JScrollPanel with stacked items inside where i check myself the visibility of each elements? Thanks

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• LINQ to SQL - Insert yielding strange behavior.

  - by Isaac

  Hi, I'm trying to insert several newly created items to the database. I have a LINQ2SQL generated class called "Order". Inside order, there's a property called "OrderItems" which is also generated by LINQ2SQL and represents the Items of that Order. So far so good. The problem I'm having right now, is when I try to add more than one newly created OrderItem inside Order. I.E: Order o = orderWorker.GetById( 10 ); for( int i=0; i < 5; ++i ) { OrderItem oi =new OrderItem { Order = order, Price = 100, ShippingPrice = 100, ShippingMethod = ... }; o.OrderItems.Add( oi ); } context.SubmitChanges(); Unfortunately, only a single entity is being added. Yes, I checked the generated SQL by adding Context.Log = Console.Out, and yes, only one statement was created. Any clues? By the way I know I'm not using InsertOnSubmit, by the documentation says: You can explicitly request Inserts by using InsertOnSubmit. Alternatively, LINQ to SQL can infer Inserts by finding objects connected to one of the known objects that must be updated. For example, if you add an Untracked object to an EntitySet(TEntity) or set an EntityRef(TEntity) to an Untracked object, you make the Untracked object reachable by way of tracked objects in the graph. While processing SubmitChanges, LINQ to SQL traverses the tracked objects and discovers any reachable persistent objects that are not tracked. Such objects are candidates for insertion into the database. Thank you very much for your time.

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• ASP.net MVC Linq-To-SQL Extended Class Field Binding

  - by user336858

  Hi there, The short version of this question is "Is there a way to get automatic View Object binding for fields defined in a partial class for a Linq-To-SQL generated class?" Apologies if it's been asked before. Example Suppose I have a typical MVC setup with the tables: Posts {PostID, ...} Categories {CategoryID, ...} A post can have more than one category, and a category can identify more than one post. Thus suppose further that I need an extra table: PostCategories {PostID, CategoryID, ...} This handles the many-to-many relationship between posts and categories. As far as I know, there's no way to do this in Linq-to-SQL right now so I have to shoehorn it in by adding a partial Postclass to the project to add that functionality. Something like: public partial class Post { public IEnumerable<Category> Categories{ get { ... } set { ... } } } So here's my question: If a user is accessing my MVC application front-end and begins editing a Post object, they might enter an invalid category. When the server recognizes the invalid input, the usual practice is to return the faulty object to the original view for re-editing along with some error messages. The fields in the edit page are re-populated with the provided values. However I don't know how to get this mechanism to work with the properties I created with the partial class as shown above. Any terminology, links, or tips you can provide would be tremendously helpful!

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• How to Implement Rich Document Editor for iPhone

  - by benjismith

  I'm just getting started on a new iPhone/iPad development project, and I need to display a document with rich styled text (potentially with embedded images). The user will touch the document, dragging to highlight individual words or multiline text spans. When the text is highlighted, a context menu will appear, letting them change the color of highlighting or add margin notes (or other various bits of structured metadata). If you're familiar with adding comments to a Word document (or annotating a PDF), then this is the same sort of thing. But in my case, the typical user will spend many many hours within the app, adding thousands (in some cases, tens of thousands) of small annotations to the central document. All of those bits of metadata will be stored locally awaiting synchronization with a remote web service. I've read other pieces of advice, where developers suggest creating a UIWebView control and passing it an HTML string. But that seems kind of clunky, especially with all the context-sensitivity that I want to include. Anyhow, I'm brand new to iPhone development and Objective-C, though I have ten years of software development experience, using a variety of languages on many different platforms, so I'm not worried about getting my hands dirty writing new functionality from scratch. But if anyone has experience building a similar kind of component, I'm interested in hearing strategies for enabling that kind of rich document markup and annotation.

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