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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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  • Change object on client side or on server side

    - by Polina Feterman
    I'm not sure what is the best practice. I have some big and complex objects (NOT flat). In that object I have many related objects - for example Invoice is the main class and one of it's properties is invoiceSupervisor - a big class by it's own called User. User can also be not flat and have department property - also an object called Department. For example I want create new Invoice. First way: I can present to client several fields to fill in. Some of them will be combos that I will need to fill with available values. For example available invoiceSupervisors. Then all the chosen values I can send to server and on server I can create new Invoice and assign all chosen values to that new Invoice. Then I will need to assign new supervisor I will pull the chosen User by id that user picked up on server from combobox. I might do some verification on the User such as does the user applicable to be invoice supervisor. Then I will assign the User object to invoiceSupervisor. Then after filling all properties I will save the new invoice. Second way: In the beginning I can call to server to get a new Invoice. Then on client I can fill all chosen values , for example I can call to server to get new User object and then fill it's id from combobox and assign the User as invoiceSupervisor. After filling the Invoice object on client I can send it to server and then the server will save the new invoice. Before saving server can run some validations as well. So what is the best approach - to make the object on client and send it to server or to collect all values from client and to make a new object on server using those values ?

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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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  • PowerShell Script To Find Where SharePoint 2007 Features Are Activated

    - by Brian T. Jackett
    Recently I posted a script to find where SharePoint 2010 Features Are Activated.  I built the original version to use SharePoint 2010 PowerShell commandlets as that saved me a number of steps for filtering and gathering features at each level.  If there was ever demand for a 2007 version I could modify the script to handle that by using the object model instead of commandlets.  Just the other week a fellow SharePoint PFE Jason Gallicchio had a customer asking about a version for SharePoint 2007.  With a little bit of work I was able to convert the script to work against SharePoint 2007.   Solution    Below is the converted script that works against a SharePoint 2007 farm.  Note: There appears to be a bug with the 2007 version that does not give accurate results against a SharePoint 2010 farm.  I ran the 2007 version against a 2010 farm and got fewer results than my 2010 version of the script.  Discussing with some fellow PFEs I think the discrepancy may be due to sandboxed features, a new concept in SharePoint 2010.  I have not had enough time to test or confirm.  For the time being only use the 2007 version script against SharePoint 2007 farms and the 2010 version against SharePoint 2010 farms.    Note: This script is not optimized for medium to large farms.  In my testing it took 1-3 minutes to recurse through my demo environment.  This script is provided as-is with no warranty.  Run this in a smaller dev / test environment first. 001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020 021 022 023 024 025 026 027 028 029 030 031 032 033 034 035 036 037 038 039 040 041 042 043 044 045 046 047 048 049 050 051 052 053 054 055 056 057 058 059 060 061 062 063 064 065 066 067 068 069 070 function Get-SPFeatureActivated { # see full script for help info, removed for formatting [CmdletBinding()] param(     [Parameter(position = 1, valueFromPipeline=$true)]     [string]     $Identity )#end param     Begin     {         # load SharePoint assembly to access object model         [void][System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint")             # declare empty array to hold results. Will add custom member for Url to show where activated at on objects returned from Get-SPFeature.         $results = @()                 $params = @{}     }     Process     {         if([string]::IsNullOrEmpty($Identity) -eq $false)         {             $params = @{Identity = $Identity}         }                 # create hashtable of farm features to lookup definition ids later         $farm = [Microsoft.SharePoint.Administration.SPFarm]::Local                         # check farm features         $results += ($farm.FeatureDefinitions | Where-Object {$_.Scope -eq "Farm"} | Where-Object {[string]::IsNullOrEmpty($Identity) -or ($_.DisplayName -eq $Identity)} |                          % {Add-Member -InputObject $_ -MemberType noteproperty -Name Url -Value ([string]::Empty) -PassThru} |                          Select-Object -Property Scope, DisplayName, Id, Url)                 # check web application features         $contentWebAppServices = $farm.services | ? {$_.typename -like "Windows SharePoint Services Web Application"}                 foreach($webApp in $contentWebAppServices.WebApplications)         {             $results += ($webApp.Features | Select-Object -ExpandProperty Definition | Where-Object {[string]::IsNullOrEmpty($Identity) -or ($_.DisplayName -eq $Identity)} |                          % {Add-Member -InputObject $_ -MemberType noteproperty -Name Url -Value $webApp.GetResponseUri(0).AbsoluteUri -PassThru} |                          Select-Object -Property Scope, DisplayName, Id, Url)                         # check site collection features in current web app             foreach($site in ($webApp.Sites))             {                 $results += ($site.Features | Select-Object -ExpandProperty Definition | Where-Object {[string]::IsNullOrEmpty($Identity) -or ($_.DisplayName -eq $Identity)} |                                  % {Add-Member -InputObject $_ -MemberType noteproperty -Name Url -Value $site.Url -PassThru} |                                  Select-Object -Property Scope, DisplayName, Id, Url)                                 # check site features in current site collection                 foreach($web in ($site.AllWebs))                 {                     $results += ($web.Features | Select-Object -ExpandProperty Definition | Where-Object {[string]::IsNullOrEmpty($Identity) -or ($_.DisplayName -eq $Identity)} |                                      % {Add-Member -InputObject $_ -MemberType noteproperty -Name Url -Value $web.Url -PassThru} |                                      Select-Object -Property Scope, DisplayName, Id, Url)                                                        $web.Dispose()                 }                 $site.Dispose()             }         }     }     End     {         $results     } } #end Get-SPFeatureActivated Get-SPFeatureActivated   Conclusion    I have posted this script to the TechNet Script Repository (click here).  As always I appreciate any feedback on scripts.  If anyone is motivated to run this 2007 version script against a SharePoint 2010 to see if they find any differences in number of features reported versus what they get with the 2010 version script I’d love to hear from you.         -Frog Out

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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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  • How do I get openssh to save my ssh identity permanently in Xfce?

    - by Alliswell
    How do I change it to save my identity permanently using Xfce? During my login session after I have entered: $ ssh-add Then identity is saved and I can connect via ssh without getting the dreaded: Enter passphrase for key However, once I logout and login back-in I get the following when running: $ ssh-add -L The agent has no identities. $ ssh <hostname> Enter passphrase for key '/home/user/.ssh/id_rsa': Stackoverflow has the following solution, yet I do not understand the reference to in the config file: IdentityFile ~/.ssh/id_rsa_buhlServer Specifically I do not understand what I would put on the identity file. Would I put the above word for word? Or just add my file: IdentityFile ~/.ssh/id_rsa StackOverflow solution

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  • How do I get openssh to save my ssh identity permanently?

    - by Alliswell
    How do I change it to save my identity permanently? During my login session after I have entered: $ ssh-add Then identity is saved and I can connect via ssh without getting the dreaded: Enter passphrase for key Once I logout and login back-in I get the following when running: $ ssh-add -L The agent has no identities. $ ssh <hostname> Enter passphrase for key '/home/user/.ssh/id_rsa': Stackoverflow has the following solution, yet I do not understand the reference to in the config file: IdentityFile ~/.ssh/id_rsa_buhlServer Specifically I do not understand what I would put on the identity file. Would I put the above word for word? Or just add my file: IdentityFile ~/.ssh/id_rsa StackOverflow solution

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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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  • How I understood monads, part 1/2: sleepless and self-loathing in Seattle

    - by Bertrand Le Roy
    For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying “oh, yeah, that’s a monad” about random stuff as if it were absolutely obvious and if I didn’t know what they were talking about, I was probably an uneducated idiot, ignorant about the simplest and most fundamental concepts of functional programming. Fair enough, I am pretty much exactly that. Being the kind of guy who can spend eight years in college just to understand a few interesting concepts about the universe, I had to check it out and try to understand monads so that I too can say “oh, yeah, that’s a monad”. Man, was I hit hard in the face with the limitations of my own abstract thinking abilities. All the articles I could find about the subject seemed to be vaguely understandable at first but very quickly overloaded the very few concept slots I have available in my brain. They also seemed to be consistently using arcane notation that I was entirely unfamiliar with. It finally all clicked together one Friday afternoon during the team’s beer symposium when Louis was patient enough to break it down for me in a language I could understand (C#). I don’t know if being intoxicated helped. Feel free to read this with or without a drink in hand. So here it is in a nutshell: a monad allows you to manipulate stuff in interesting ways. Oh, OK, you might say. Yeah. Exactly. Let’s start with a trivial case: public static class Trivial { public static TResult Execute<T, TResult>( this T argument, Func<T, TResult> operation) { return operation(argument); } } This is not a monad. I removed most concepts here to start with something very simple. There is only one concept here: the idea of executing an operation on an object. This is of course trivial and it would actually be simpler to just apply that operation directly on the object. But please bear with me, this is our first baby step. Here’s how you use that thing: "some string" .Execute(s => s + " processed by trivial proto-monad.") .Execute(s => s + " And it's chainable!"); What we’re doing here is analogous to having an assembly chain in a factory: you can feed it raw material (the string here) and a number of machines that each implement a step in the manufacturing process and you can start building stuff. The Trivial class here represents the empty assembly chain, the conveyor belt if you will, but it doesn’t care what kind of raw material gets in, what gets out or what each machine is doing. It is pure process. A real monad will need a couple of additional concepts. Let’s say the conveyor belt needs the material to be processed to be contained in standardized boxes, just so that it can safely and efficiently be transported from machine to machine or so that tracking information can be attached to it. Each machine knows how to treat raw material or partly processed material, but it doesn’t know how to treat the boxes so the conveyor belt will have to extract the material from the box before feeding it into each machine, and it will have to box it back afterwards. This conveyor belt with boxes is essentially what a monad is. It has one method to box stuff, one to extract stuff from its box and one to feed stuff into a machine. So let’s reformulate the previous example but this time with the boxes, which will do nothing for the moment except containing stuff. public class Identity<T> { public Identity(T value) { Value = value; } public T Value { get; private set;} public static Identity<T> Unit(T value) { return new Identity<T>(value); } public static Identity<U> Bind<U>( Identity<T> argument, Func<T, Identity<U>> operation) { return operation(argument.Value); } } Now this is a true to the definition Monad, including the weird naming of the methods. It is the simplest monad, called the identity monad and of course it does nothing useful. Here’s how you use it: Identity<string>.Bind( Identity<string>.Unit("some string"), s => Identity<string>.Unit( s + " was processed by identity monad.")).Value That of course is seriously ugly. Note that the operation is responsible for re-boxing its result. That is a part of strict monads that I don’t quite get and I’ll take the liberty to lift that strange constraint in the next examples. To make this more readable and easier to use, let’s build a few extension methods: public static class IdentityExtensions { public static Identity<T> ToIdentity<T>(this T value) { return new Identity<T>(value); } public static Identity<U> Bind<T, U>( this Identity<T> argument, Func<T, U> operation) { return operation(argument.Value).ToIdentity(); } } With those, we can rewrite our code as follows: "some string".ToIdentity() .Bind(s => s + " was processed by monad extensions.") .Bind(s => s + " And it's chainable...") .Value; This is considerably simpler but still retains the qualities of a monad. But it is still pointless. Let’s look at a more useful example, the state monad, which is basically a monad where the boxes have a label. It’s useful to perform operations on arbitrary objects that have been enriched with an attached state object. public class Stateful<TValue, TState> { public Stateful(TValue value, TState state) { Value = value; State = state; } public TValue Value { get; private set; } public TState State { get; set; } } public static class StateExtensions { public static Stateful<TValue, TState> ToStateful<TValue, TState>( this TValue value, TState state) { return new Stateful<TValue, TState>(value, state); } public static Stateful<TResult, TState> Execute<TValue, TState, TResult>( this Stateful<TValue, TState> argument, Func<TValue, TResult> operation) { return operation(argument.Value) .ToStateful(argument.State); } } You can get a stateful version of any object by calling the ToStateful extension method, passing the state object in. You can then execute ordinary operations on the values while retaining the state: var statefulInt = 3.ToStateful("This is the state"); var processedStatefulInt = statefulInt .Execute(i => ++i) .Execute(i => i * 10) .Execute(i => i + 2); Console.WriteLine("Value: {0}; state: {1}", processedStatefulInt.Value, processedStatefulInt.State); This monad differs from the identity by enriching the boxes. There is another way to give value to the monad, which is to enrich the processing. An example of that is the writer monad, which can be typically used to log the operations that are being performed by the monad. Of course, the richest monads enrich both the boxes and the processing. That’s all for today. I hope with this you won’t have to go through the same process that I did to understand monads and that you haven’t gone into concept overload like I did. Next time, we’ll examine some examples that you already know but we will shine the monadic light, hopefully illuminating them in a whole new way. Realizing that this pattern is actually in many places but mostly unnoticed is what will enable the truly casual “oh, yes, that’s a monad” comments. Here’s the code for this article: http://weblogs.asp.net/blogs/bleroy/Samples/Monads.zip The Wikipedia article on monads: http://en.wikipedia.org/wiki/Monads_in_functional_programming This article was invaluable for me in understanding how to express the canonical monads in C# (interesting Linq stuff in there): http://blogs.msdn.com/b/wesdyer/archive/2008/01/11/the-marvels-of-monads.aspx

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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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  • Class hierarchy problem in this social network model

    - by Gerenuk
    I'm trying to design a class system for a social network data model - basically a link/object system. Now I have roughly the following structure (simplified and only relevant methods shown) class Data: "used to handle the data with mongodb" "can link, unlink data and also return other linked data" "is basically a proxy object that only stores _id and accesses mongodb on requests" "it looks like {_id: ..., _out: [id1, id2,...], _inc: [id3, id4, ...]}" def get_node(self, id) "create a new Data object from the underlying mongodb" "each data object can potentially create a reference object to new mongo data" "this is needed when the data returns the linked objects" class Node: """ this class proxies linking calls to .data it includes additional network logic operations whereas Data only contains a basic database solution """ def __init__(self, data): "the infrastructure realization is stored as composition by an included object data" "Node bascially proxies most calls to the infrastructure object data" def get_node(self, data): "creates a new object of class Object or Link depending on data" class Object(Node): "can have multiple connections to Link" class Link(Node): "has one 'in' and one 'out' connection to an Object" This system is working, however maybe wouldn't work outside Python. Note that after reading links Now I have two questions here: 1) I want to infrastructure of the data storage to be replacable. Earlier I had Data as a superclass of Node so that it provided the neccessary calls. But (without dirty Python tricks) you cannot replace the superclass dynamically. Is using composition therefore recommended? The drawback is that I have to proxy most calls (link, unlink etc). Any thoughts? 2) The class Node contains the common method .get_node which is used to built new Object or Link instances after reading out the data. Some attribute of data decided whether the object which is only stored by id should be instantiated as an Object or Link class. The problem here is that Node needs to know about Object and Link in advance, which seems dodgy. Do you see a different solution? Both Object and Link need to instantiate one of all possible types depending on what the find in their linked data. Are there any other ideas how to implement a flexible Object/Link structure where the underlying database storage is isolated?

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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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  • 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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  • 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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  • Good style for handling constructor failure of critical object

    - by mtlphil
    I'm trying to decide between two ways of instantiating an object & handling any constructor exceptions for an object that is critical to my program, i.e. if construction fails the program can't continue. I have a class SimpleMIDIOut that wraps basic Win32 MIDI functions. It will open a MIDI device in the constructor and close it in the destructor. It will throw an exception inherited from std::exception in the constructor if the MIDI device cannot be opened. Which of the following ways of catching constructor exceptions for this object would be more in line with C++ best practices Method 1 - Stack allocated object, only in scope inside try block #include <iostream> #include "simplemidiout.h" int main() { try { SimpleMIDIOut myOut; //constructor will throw if MIDI device cannot be opened myOut.PlayNote(60,100); //..... //myOut goes out of scope outside this block //so basically the whole program has to be inside //this block. //On the plus side, it's on the stack so //destructor that handles object cleanup //is called automatically, more inline with RAII idiom? } catch(const std::exception& e) { std::cout << e.what() << std::endl; std::cin.ignore(); return 1; } std::cin.ignore(); return 0; } Method 2 - Pointer to object, heap allocated, nicer structured code? #include <iostream> #include "simplemidiout.h" int main() { SimpleMIDIOut *myOut; try { myOut = new SimpleMIDIOut(); } catch(const std::exception& e) { std::cout << e.what() << std::endl; delete myOut; return 1; } myOut->PlayNote(60,100); std::cin.ignore(); delete myOut; return 0; } I like the look of the code in Method 2 better, don't have to jam my whole program into a try block, but Method 1 creates the object on the stack so C++ manages the object's life time, which is more in tune with RAII philosophy isn't it? I'm still a novice at this so any feedback on the above is much appreciated. If there's an even better way to check for/handle constructor failure in a siatuation like this please let me know.

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  • Sql Server: all object dependencies

    - by Gjorgji
    Hi, Is there any place where I can find all possible object dependencies in Sql Server? What I mean by "object dependency" is a list of object that one object can depend on. For example, TABLE can depend on SCHEMA, TYPE, TABLE, FUNCTION, etc.

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  • C#: returns array from object.

    - by jitm
    Hello, There is the next task: I need to check if input parameter (object) is array, then return array of input elements. For example I have input array like this: int [] array = {1,2,3,4}; And method private object[] GetArray(object @from) { } So, I need to check in this method that input variable is array and after return this array. For checking I use if(@from.GetType().IsArray) And how to create array from object ??? Is it possible ? Thanks.

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  • using object in multiple function

    - by nixon
    Hi. How can i use object from one function in another ? main() { private void button1_click { MyClass object = new MyClass(); object.blabla(); } private void button2_click { // how can i use object from button1_click ?? } }

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