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• Javascript function objects, this keyword points to wrong object

  - by Rody van Sambeek

  I've got a problem concerning the javascript "this" keyword when used within a javascript functional object. I want to be able to create an object for handling a Modal popup (JQuery UI Dialog). The object is called CreateItemModal. Which i want to be able to instantiate and pass some config settings. One of the config settings. When the show method is called, the dialog will be shown, but the cancel button is not functioning because the this refers to the DOM object instead of the CreateItemModal object. How can I fix this, or is there a better approach to put seperate behaviour in seperate "classes" or "objects". I've tried several approaches, including passing the "this" object into the events, but this does not feel like a clean solution. See (simplified) code below: function CreateItemModal(config) { // initialize some variables including $wrapper }; CreateItemModal.prototype.show = function() { this.$wrapper.dialog({ buttons: { // this crashes because this is not the current object here Cancel: this.close } }); }; CreateItemModal.prototype.close = function() { this.config.$wrapper.dialog('close'); };

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• Javascript cloned object looses its prototype functions

  - by Jake M

  I am attempting to clone an object in Javascript. I have made my own 'class' that has prototype functions. My Problem: When I clone an object, the clone cant access/call any prototype functions. I get an error when I go to access a prototype function of the clone: clone.render is not a function Can you tell me how I can clone an object and keep its prototype functions This simple JSFiddle demonstrates the error I get: http://jsfiddle.net/VHEFb/1/ function cloneObject(obj) { // Handle the 3 simple types, and null or undefined if (null == obj || "object" != typeof obj) return obj; // Handle Date if (obj instanceof Date) { var copy = new Date(); copy.setTime(obj.getTime()); return copy; } // Handle Array if (obj instanceof Array) { var copy = []; for (var i = 0, len = obj.length; i < len; ++i) { copy[i] = cloneObject(obj[i]); } return copy; } // Handle Object if (obj instanceof Object) { var copy = {}; for (var attr in obj) { if (obj.hasOwnProperty(attr)) copy[attr] = cloneObject(obj[attr]); } return copy; } throw new Error("Unable to copy obj! Its type isn't supported."); } function MyObject(name) { this.name = name; // I have arrays stored in this object also so a simple cloneNode(true) call wont copy those // thus the need for the function cloneObject(); } MyObject.prototype.render = function() { alert("Render executing: "+this.name); } var base = new MyObject("base"); var clone = cloneObject(base); clone.name = "clone"; base.render(); clone.render(); // Error here: "clone.render is not a function"

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• How to cancel a deeply nested process

  - by Mystere Man

  I have a class that is a "manager" sort of class. One of it's functions is to signal that the long running process of the class should shut down. It does this by setting a boolean called "IsStopping" in class. public class Foo { bool isStoping void DoWork() { while (!isStopping) { // do work... } } } Now, DoWork() was a gigantic function, and I decided to refactor it out and as part of the process broke some of it into other classes. The problem is, Some of these classes also have long running functions that need to check if isStopping is true. public class Foo { bool isStoping void DoWork() { while (!isStopping) { MoreWork mw = new MoreWork() mw.DoMoreWork() // possibly long running // do work... } } } What are my options here? I have considered passing isStopping by reference, which I don't really like because it requires there to be an outside object. I would prefer to make the additional classes as stand alone and dependancy free as possible. I have also considered making isStopping a property, and then then having it call an event that the inner classes could be subscribed to, but this seems overly complex. Another option was to create a "Process Cancelation Token" class, similar to what .net 4 Tasks use, then that token be passed to those classes. How have you handled this situation? EDIT: Also consider that MoreWork might have a EvenMoreWork object that it instantiates and calls a potentially long running method on... and so on. I guess what i'm looking for is a way to be able to signal an arbitrary number of objects down a call tree to tell them to stop what they're doing and clean up and return.

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• Pass object or id

  - by Charles

  This is just a question about best practices. Imagine you have a method that takes one parameter. This parameter is the id of an object. Ideally, I would like to be able to pass either the object's id directly, or just the object itself. What is the most elegant way to do this? I came up with the following: def method_name object object_id = object.to_param.to_i ### do whatever needs to be done with that object_id end So, if the parameter already is an id, it just pretty much stays the same; if it's an object, it gets its id. This works, but I feel like this could be better. Also, to_param returns a string, which could in some cases return a "real" string (i.e. "string" instead of "2"), hence returning 0 upon calling to_i on it. This could happen, for example, when using the friendly id gem for classes. Active record offers the same functionality. It doesn't matter if you say: Table.where(user_id: User.first.id) # pass in id or Table.where(user_id: User.first) # pass in object and infer id How do they do it? What is the best approach to achieve this effect?

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• WPF Databinding With A Collection Object

  - by Randster

  Argh, although I've been googling, I really would appreciate it if someone could break my problem down as all the code examples online are confusing me more than assisting (perhaps it's just late)... I have a simple class as defined below: public class Person { int _id; string _name; public Person() { } public int ID { get { return _id; } set { _id = value; } } public string Name { get { return _name; } set { _name = value; } } } that is stored in a database, and thru a bit more code I put it into an ObservableCollection object to attempt to databind in WPF later on: public class People : ObservableCollection<Person> { public People() : base() { } public void Add(List<Person> pListOfPeople) { foreach (Person p in pListOfPeople) this.Add(p); } } In XAML, I have myself a ListView that I would like to populate a ListViewItem (consisting of a textblock) for each item in the "People" object as it gets updated from the database. I would also like that textblock to bind to the "Name" property of the Person object. I thought at first that I could do this: lstPeople.DataContext = objPeople; where lstPeople is my ListView control in my XAML, but that of course does nothing. I've found TONS of examples online where people through XAML create an object and then bind to it through their XAML; but not one where we bind to an instantiated object and re-draw accordingly. Could someone please give me a few pointers on: A) How to bind a ListView control to my instantiated "People" collection object? B) How might I apply a template to my ListView to format it for the objects in the collection? Even links to a decent example (not one operating on an object declared in XAML please) would be appreciated. Thanks for your time.

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• Making the domain-model of tic tac toe

  - by devoured elysium

  I am trying to make the domain model of a Tic Tac Toe game. I'll try then to go on through the various steps of the Unified Process and later implement it in some language (C# or Java). I'd like to have some feedback if I'm going on the right path: I've defined the game with two actors, Player O and Player X. I'm not sure about defining both a Tile and a Tile State. Maybe I should only define a Tile and have the 3 possible states specialize from it? I'm not sure what is best: to have both Player O and Player X be associations with Tic Tac Toe or have them inherit from Player that is associated with Tic Tac Toe. Following the design shown on the pic, in theory we could have a Tic Tac Toe concept with 2 Player O's, which wouldn't be correct. What is your opinion on this? Also, am I missing something in the diagram? Although I can't see any other actors for Tic Tac Toe, should I have any other? Thanks

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• How much abstraction is too much?

  - by Daniel Bingham

  In an Object Oriented Program: How much abstraction is too much? How much is just right? I have always been a nuts and bolts kind of guy. I understood the concept behind high levels of encapsulation and abstraction, but always felt instinctively that adding too much would just confuse the program. I always tried to shoot for an amount of abstraction that left no empty classes or layers. And where in doubt, instead of adding a new layer to the hierarchy, I would try and fit something into the existing layers. However, recently I've been encountering more highly abstracted systems. Systems where everything that could require a representation later in the hierarchy gets one up front. This leads to a lot of empty layers, which at first seems like bad design. However, on second thought I've come to realize that leaving those empty layers gives you more places to hook into in the future with out much refactoring. It leaves you greater ability to add new functionality on top of the old with out doing nearly as much work to adjust the old. The two risks of this seem to be that you could get the layers you need wrong. In this case one would wind up still needing to do substantial refactoring to extend the code and would still have a ton of never used layers. But depending on how much time you spend coming up with the initial abstractions, the chance of screwing it up, and the time that could be saved later if you get it right - it may still be worth it to try. The other risk I can think of is the risk of over doing it and never needing all the extra layers. But is that really so bad? Are extra class layers really so expensive that it is much of a loss if they are never used? The biggest expense and loss here would be time that is lost up front coming up with the layers. But much of that time still might be saved later when one can work with the abstracted code rather than more low level code. So when is it too much? At what point do the empty layers and extra "might need" abstractions become overkill? How little is too little? Where's the sweet spot? Are there any dependable rules of thumb you've found in the course of your career that help you judge the amount of abstraction needed?

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• Repeating fields in similar database tables

  - by user1738833

  I have been tasked with working on a database that I have never seen before and I'm looking at the DB structure. Some of the central and most heavily queried and joined tables look like virtual duplicates of each other. Here's a massively simplified representation of the situation, with business-sensitive information changed, listing hypothetical table names and fields: TopLevelGroup: PK_TLGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubGroup: PK_SubGroupId, FK_ParentTopLevelGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubSubGroup: PK_SubSUbGroupId, FK_ParentSubGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK I haven't listed the types of the fields as I don't think it's particularly important to the situation. In addition, it's worth saying that rather than four repeated fields as in the example above, I'm looking at 86 repeated fields. For the most part, those fields genuinely do represent "facts" about the primary table entity, so it's not automatically wrong for that reason. In addition, the "groups" represented here have a property inheritance relationship. If DisplaysXOnBill is NULL in the SubSubGroup, it takes the value of DisplaysXOnBillfrom it's parent, the SubGroup, and so-on up to the TopLevelGroup. Further, the requirements will never require that the model extends beyond three levels, so there is no need for flexibility in that area. Is there a design smell from several tables which describe very similar entities having almost identical fields? If so, what might be a better design of the example above? I'm using the phrase "design smell" to indicate a possible problem. Of course, in any given situation, a particular design might well be the best solution. I'm looking for a more general answer - wondering what might be wrong with this design and what might be the better design were that the case. Possibly related, but not primary questions: Is this database schema in a reasonably normal form (e.g. to 3NF), insofar as can be told from the information I've provided. I can't see a problem with the requirements of 2NF and 3NF, except in their inheriting the requirements of 1NF. Is 1NF satisfied though? Are repeating groups allowed in different tables? Is there a best-practice method for implementing the inheritance relationship in a database as I require? The method above feels clunky to me because any query on the SubSubGroup necessarily needs to join onto the SubGroup and the TopLevelGroup tables to collect inherited facts, which can make even trivial joins requiring facts from the SubSubGroup table rather long-winded. There are, of course, political considerations to making a relatively large change like this. For the purpose of this question, I'm happy to ignore that fact in the interests of keeping the answers ring-fenced to the technical problem.

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• Is deriving square from rectangle a violation of Liskov's Substitution Principle?

  - by somaraj

  I am new to design and learning the design principles. It says deriving square from rectangle is a classic example of violation of Liskov's Substitution Principle. If that's the case, what should be the correct design?

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• Class architecture, no friends allowed

  - by Captain Comic

  The question of why there are no friends in C# has been extensively discussed. I have the following design problems. I have a class that has only one public function AddOrder(Order ord). Clients are allowed to call only this function. All other logic must be hidden. Order class is listening to market events and must call other other function of TradingSystem ExecuteOrder, so I have to make it public as well. Doing that I will allow clients of Trading system to call this function and I don't want that. class TradingSystem { // Trading system stores list of orders List<Order> _orders; // this function is made public so that Order can call ir public ExecuteOrder(Order ord) { } // this function is made public for external clients public AddOrder(OrderRequest ordreq) { // create order and pass it this order.OnOrderAdded(this); } } class Order { TradingSystem _ts; public void OnOrderAdded(TradingSystem ts) { _ts = ts; } void OnMarketEvent() { _ts.ExecuteOrder() } }

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• What are the differences between struct and class in C++

  - by palm3D

  This question was already asked in the context of C#/.Net. Now I'd like to learn the differences between a struct and a class in (unmanaged) C++. Please discuss the technical differences as well as reasons for choosing one or the other in OO design. I'll start with an obvious difference: If you don't specify public: or private:, members of a struct are public by default; members of a class are private by default. I'm sure there are other differences to be found in the obscure corners of the C++ specification.

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• Apache2 server does not start cannot pen shared object file

  - by sid__

  I am working with Apache and Passenger for a Rails project. And a during a restart I got the following error Cannot load /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11/ext/apache2/mod_passenger.so into server: /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11/ext/apache2/mod_passenger.so: cannot open shared object file: No such file or directory However there is no change in the apache configuration file. I have attached the snippet from the conf file 287 LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11/ext/apache2/mod_passenger.so 288 PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-2.2.11 289 PassengerRuby /usr/bin/ruby1.8 I am also unable to locate the shared object file in the location pointed to by the server though I am not really sure how the .so file is works (created/destroyed) I would also appreciate it if someone could explain to me what exactly has happened. I understand the shared object file is mission, what could be the reason it got deleted.

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• Partial Trust in WPF 4

  - by Hadi Eskandari

  I've started a new project in WPF 4 (.NET 4) and trying to see if I can run it in xbap mode. I need to run the application in Full Trust with the new mode made available in .NET 4 which asks the end user if the full trust application should be run. I've set the "Security" mode to "Full Trust" application, and it builds just fine. When I run it, an exception is thrown and IE error message shows the following error. Any ways around it?? Startup URI: T:\projects\Hightech Sources\PayRoll\PayRoll.Web\publish\PayRoll.Web.xbap Application Identity: file:///T:/projects/Hightech%20Sources/PayRoll/PayRoll.Web/publish/PayRoll.Web.xbap#PayRoll.Web.xbap, Version=1.0.0.0, Culture=neutral, PublicKeyToken=1d910f49755d2c97, processorArchitecture=msil/PayRoll.Web.exe, Version=1.0.0.0, Culture=neutral, PublicKeyToken=1d910f49755d2c97, processorArchitecture=msil, type=win32 System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) at System.Security.CodeAccessSecurityEngine.Check(CodeAccessPermission cap, StackCrawlMark& stackMark) at System.Security.CodeAccessPermission.Demand() at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection, Boolean suppressSecurityChecks) at System.Reflection.RuntimeAssembly.InternalLoadFrom(String assemblyFile, Evidence securityEvidence, Byte[] hashValue, AssemblyHashAlgorithm hashAlgorithm, Boolean forIntrospection, Boolean suppressSecurityChecks, StackCrawlMark& stackMark) at System.Reflection.Assembly.LoadFrom(String assemblyFile) at PayRoll.Web.App.SelectAssemblies() at Caliburn.PresentationFramework.ApplicationModel.CaliburnApplication..ctor() at PayRoll.Web.App..ctor() at PayRoll.Web.App.Main() at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.Runtime.Hosting.ManifestRunner.Run(Boolean checkAptModel) at System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly() at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData) at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext) at System.Windows.Interop.PresentationApplicationActivator.CreateInstance(ActivationContext actCtx) at System.Activator.CreateInstance(ActivationContext activationContext) at System.AppDomain.Setup(Object arg) at System.AppDomain.nCreateInstance(String friendlyName, AppDomainSetup setup, Evidence providedSecurityInfo, Evidence creatorsSecurityInfo, IntPtr parentSecurityDescriptor) at System.Runtime.Hosting.ApplicationActivator.CreateInstanceHelper(AppDomainSetup adSetup) at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData) at System.Windows.Interop.PresentationApplicationActivator.CreateInstance(ActivationContext actCtx) at System.Activator.CreateInstance(ActivationContext activationContext) at System.Deployment.Application.DeploymentManager.ExecuteNewDomain() at System.Deployment.Application.InPlaceHostingManager.Execute() at MS.Internal.AppModel.XappLauncherApp.ExecuteDownloadedApplication() at System.Windows.Interop.DocObjHost.RunApplication(ApplicationRunner runner) at MS.Internal.AppModel.XappLauncherApp.XappLauncherApp_Exit(Object sender, ExitEventArgs e) at System.Windows.Application.OnExit(ExitEventArgs e) at System.Windows.Application.DoShutdown() at System.Windows.Application.ShutdownImpl() at System.Windows.Application.ShutdownCallback(Object arg) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.StartDispatcherInBrowser(Object unused) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) The action that failed was: Demand The type of the first permission that failed was: System.Security.Permissions.FileIOPermission

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• NHibernate IUserType convert nullable DateTime to DB not-null value

  - by barakbbn

  I have legacy DB that store dates that means no-date as 9999-21-31, The column Till_Date is of type DateTime not-null="true". in the application i want to build persisted class that represent no-date as null, So i used nullable DateTime in C# //public DateTime? TillDate {get; set; } I created IUserType that knows to convert the entity null value to DB 9999-12-31 but it seems that NHibernate doesn't call SafeNullGet, SafeNullSet on my IUserType when the entity value is null, and report a null is used for not-null column. I tried to by-pass it by mapping the column as not-null="false" (changed only the mapping file, not the DB) but it still didn't help, only now it tries to insert the null value to the DB and get ADOException. Any knowledge if NHibernate doesn't support IUseType that convert null to not-null values? Thanks //Implementation public class NullableDateTimeToNotNullUserType : IUserType { private static readonly DateTime MaxDate = new DateTime(9999, 12, 31); public new bool Equals(object x, object y) { //This didn't work as well if (ReferenceEquals(x, y)) return true; //if(x == null && y == null) return false; if (x == null || y == null) return false; return x.Equals(y); } public int GetHashCode(object x) { return x == null ? 0 : x.GetHashCode(); } public object NullSafeGet(IDataReader rs, string[] names, object owner) { var value = rs.GetDateTime(rs.GetOrdinal(names[0])); return (value == MaxDate)? null : value; } public void NullSafeSet(IDbCommand cmd, object value, int index) { var dateValue = (DateTime?)value; var dbValue = (dateValue.HasValue) ? dateValue.Value : MaxDate; ((IDataParameter)cmd.Parameters[index]).Value = dbValue; } public object DeepCopy(object value) { return value; } public object Replace(object original, object target, object owner) { return original; } public object Assemble(object cached, object owner) { return cached; } public object Disassemble(object value) { return value; } public SqlType[] SqlTypes { get { return new[] { NHibernateUtil.DateTime.SqlType }; } } public Type ReturnedType { get { return typeof(DateTime?); } } public bool IsMutable { get { return false; } } } } //Final Implementation with fixes. make the column mapping in hbm.xml not-null="false" public class NullableDateTimeToNotNullUserType : IUserType { private static readonly DateTime MaxDate = new DateTime(9999, 12, 31); public new bool Equals(object x, object y) { //This didn't work as well if (ReferenceEquals(x, y)) return true; //if(x == null && y == null) return false; if (x == null || y == null) return false; return x.Equals(y); } public int GetHashCode(object x) { return x == null ? 0 : x.GetHashCode(); } public object NullSafeGet(IDataReader rs, string[] names, object owner) { var value = NHibernateUtil.Date.NullSafeGet(rs, names[0]); return (value == MaxDate)? default(DateTime?) : value; } public void NullSafeSet(IDbCommand cmd, object value, int index) { var dateValue = (DateTime?)value; var dbValue = (dateValue.HasValue) ? dateValue.Value : MaxDate; NHibernateUtil.Date.NullSafeSet(cmd, valueToSet, index); } public object DeepCopy(object value) { return value; } public object Replace(object original, object target, object owner) { return original; } public object Assemble(object cached, object owner) { return cached; } public object Disassemble(object value) { return value; } public SqlType[] SqlTypes { get { return new[] { NHibernateUtil.DateTime.SqlType }; } } public Type ReturnedType { get { return typeof(DateTime?); } } public bool IsMutable { get { return false; } } } }

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• General advice and guidelines on how to properly override object.GetHashCode()

  - by Svish

  According to MSDN, a hash function must have the following properties: If two objects compare as equal, the GetHashCode method for each object must return the same value. However, if two objects do not compare as equal, the GetHashCode methods for the two object do not have to return different values. The GetHashCode method for an object must consistently return the same hash code as long as there is no modification to the object state that determines the return value of the object's Equals method. Note that this is true only for the current execution of an application, and that a different hash code can be returned if the application is run again. For the best performance, a hash function must generate a random distribution for all input. I keep finding myself in the following scenario: I have created a class, implemented IEquatable<T> and overridden object.Equals(object). MSDN states that: Types that override Equals must also override GetHashCode ; otherwise, Hashtable might not work correctly. And then it usually stops up a bit for me. Because, how do you properly override object.GetHashCode()? Never really know where to start, and it seems to be a lot of pitfalls. Here at StackOverflow, there are quite a few questions related to GetHashCode overriding, but most of them seems to be on quite particular cases and specific issues. So, therefore I would like to get a good compilation here. An overview with general advice and guidelines. What to do, what not to do, common pitfalls, where to start, etc. I would like it to be especially directed at C#, but I would think it will work kind of the same way for other .NET languages as well(?). I think maybe the best way is to create one answer per topic with a quick and short answer first (close to one-liner if at all possible), then maybe some more information and end with related questions, discussions, blog posts, etc., if there are any. I can then create one post as the accepted answer (to get it on top) with just a "table of contents". Try to keep it short and concise. And don't just link to other questions and blog posts. Try to take the essence of them and then rather link to source (especially since the source could disappear. Also, please try to edit and improve answers instead of created lots of very similar ones. I am not a very good technical writer, but I will at least try to format answers so they look alike, create the table of contents, etc. I will also try to search up some of the related questions here at SO that answers parts of these and maybe pull out the essence of the ones I can manage. But since I am not very stable on this topic, I will try to stay away for the most part :p

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• Private constructor and public parameter constructor -C#

  - by Amutha

  I heard that private constructor prevent object creation from outside world. When i have a code public class Product { public string Name { get;set;} public double Price {get;set;} Product() { } public Product(string _name,double _price) { } } here still i can declare public constructor(parameter),won't it spoil the purpose of private constructor? When do we need both private and public constructor(parameter) in code? I need detailed explanation please.

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• Embedded Office Application - How to know whether the app is running or the object is embedded

  - by A9S6

  I am adding an Excel Worksheet object inside Word. Excel has a COM addin attached to it. Any idea how one can know whether Excel is running independently or as an embedded object? The COM Addin attached to Excel loads when the embedded Excel object is activated (double-clicked) inside Word. I am looking for some kind of a property or a parameter in OnConnection(...) or other method that can tell the state of Excel object.

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• Retrieving Data related to a top-level object from parse.com using PHP

  - by Albeert Tw

  I am retrieve related data using parse.com and PHP I get the top-leve object without problems but I can't access related data. ([myRelation] => stdClass Object ( [__type] => Relation [className] => other)) Please refer to my code below: $className = "myClass"; $url = 'https://api.parse.com/1/classes/' . $className; $appId = 'xxxxxx'; $restKey = 'xxxxxxx'; $relatedParams = urlencode('include=people'); $rest = curl_init(); curl_setopt($rest, CURLOPT_SSL_VERIFYPEER, false); curl_setopt($rest, CURLOPT_URL, $url .'/io1GzkzErH/'.$relatedParams); curl_setopt($rest, CURLOPT_HTTPGET, true); curl_setopt($rest, CURLOPT_RETURNTRANSFER, true); curl_setopt($rest, CURLOPT_HTTPHEADER, array("X-Parse-Application-Id: " . $appId, "X-Parse-REST-API-Key: " . $restKey, "Content-Type: application/json")); $response = curl_exec($rest); echo $response; I want to see related objects into myRelation. Current answer is: I get this answer: stdClass Object ( [Altres] => loremipsum. [Cartell] => stdClass Object ( [__type] => File [name] => f29efff4-5db1-451a-ab42-7569fbb955a7-cartell.jpg [url] => loremipsum.jpg ) [CartellURL] => [Categoria] => Comedia [Durada] => 120min [Estat] => Al teatre [Final] => stdClass Object ( [__type] => Date [iso] => 2014-06-18T22:00:00.000Z ) [Inici] => stdClass Object ( [__type] => Date [iso] => 2014-04-25T22:00:00.000Z ) [Nom] => Losers [Prioritat] => 0 [Sala] => loremipsum [Sinopsis] => loremipsum [TrailerURL] => loremipsum.com [URLEntrada] => loremipsum.com [URLProductora] => http://www.loremipsum.com [Visible] => 1 [createdAt] => 2014-05-20T12:01:06.094Z [objectId] => io1GzkzErH [people] => stdClass Object ( [__type] => Relation [className] => persones ) [updatedAt] => 2014-05-20T12:07:22.758Z ) loremipsum But I need to know what are in [people] = stdClass Object ( [__type] = Relation [className] = persones )

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• casing the object values

  - by deep

  Hai am using telerik wpf grid in grid selection change event am getting the selected row values. the problem is the values are as object. object myData = radGridView.SelectedItem; the object myData contains the row values. but i don know how to get values from the myData object

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• Attribute References in Python

  - by Jeune

  I do Java programming and recently started learning Python via the official documentation. I see that we can dynamically add data attributes to an instance object unlike in Java: class House: pass my_house = House() my_house.number = 40 my_house.rooms = 8 my_house.garden = 1 My question is, in what situations is this feature used? What are the advantages and disadvantages compared to the way it is done in Java?

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• Java object to XML Elements?

  - by DaveKub

  I'm working on a webservices client app and I have it mostly working. I can retrieve and read data from the third-party webservice fine. Now I need to submit some data and I'm stuck. The classes for the objects I'm retrieving/submitting were generated from XSD files via the xjc tool. The part I'm stuck on is turning one of those objects into an XML tree to submit to the webservice. When I retrieve/send a request from/to the ws, it contains a 'payload' object. This is defined in java code as (partial listing): @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "PayloadType", propOrder = { "compressed", "document", "any", "format" }) public class PayloadType { @XmlElement(name = "Compressed") protected String compressed; @XmlElement(name = "Document") protected List<String> document; @XmlAnyElement protected List<Element> any; protected String format; public List<Element> getAny() { if (any == null) { any = new ArrayList<Element>(); } return this.any; } } The only field I'm concerned with is the 'any' field which contains an XML tree. When I retrieve data from the ws, I read that field with something like this: ('root' is of org.w3c.dom.Element type and is the result of calling 'getAny().get(0)' on the payload object) NodeList nl = root.getElementsByTagName("ns1:Process"); // "ns1:Process" is an XML node to do something with if (nl != null && nl.getLength() > 0) { for (int i = 0; i < nl.getLength(); i++) { Element proc = (Element) nl.item(i); try { // do something with the 'proc' Element here... } catch (Exception ex) { // handle problems here... } } } Submitting data is where I'm stuck. How do I take a java object created from one of the classes generated from XSD and turn it into an Element object that I can add to the 'any' List of the payload object?? For instance, if I have a DailyData class and I create and populate it with data: DailyData dData = new DailyData(); dData.setID = 34; dData.setValues = "3,5,76,23"; How do I add that 'dData' object to the 'any' List of the payload object? It has to be an Element. Do I do something with a JAXBContext marshaller? I've used that to dump the 'dData' object to the screen to check the XML structure. I'm sure the answer is staring me in the face but I just can't see it! Dave

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• How to add entity object to adequate entity set with object context in EF?

  - by Levelbit

  I have a problem when I add an entity object with ObjectContext.AddObject method because I can't retrieve that object with LINQ querying my ObjectContext.Person entities. I know that this new added object is stored somewhere, because it is used to update database after SaveChanges method. That's bothers me because I want to update my datagrid DataContext without saving changes unless I really want to do it. It doesn't help if I add the same object to DataContext list myself directly.

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• Java Object class

  - by SHiNKiROU

  I have a weird Java question: As we know: All Java classes extend java.lang.Object All Java classes cannot extend itself Then, java.lang.Object must extend java.lang.Object, which is itself, therefore, it should be impossible. How is Object implemented in Java?

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• Java Object superclass

  - by SHiNKiROU

  I have a weird Java question: As we know: All Java classes extend java.lang.Object All Java classes cannot extend itself Then, java.lang.Object must extend java.lang.Object, which is itself, therefore, it should be impossible. How is Object implemented in Java?

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• const object and const constructor

  - by Muhammad alaa

  Is there any way to know if an object is a const object or regular object, for instance consider the following class class String { String(const char* str); }; if user create a const object from String then there is no reason to copy the passed native string and that because he will not make any manipulation on it, the only thing he will do is get string size, string search and other functions that will not change the string.

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