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  • Object reference not set to an instance of an object - how to find the offending object name in the

    - by Jason
    This is the bane of my programming existence. After deploying an application, when this error crops up, no amount of debug dump tells you WHAT object was not instantiated. I have the call stack, that's great, it tells me roughly where the object is, but is there any way to get .NET to tell me the actual name of the object? If you catch them while debugging, of course the program breaks right on the offending creature, but if it happens after the program is in the wild, good luck. There has to be a way. I've explored the exceptions returned in these instances and there is just nothing helpful.

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  • In what circumstances are instance variables declared as '_var' in 'use fields' private?

    - by Pedro Silva
    I'm trying to understand the behavior of the fields pragma, which I find poorly documented, regarding fields prefixed with underscores. This is what the documentation has to say about it: Field names that start with an underscore character are made private to the class and are not visible to subclasses. Inherited fields can be overridden but will generate a warning if used together with the -w switch. This is not consistent with its actual behavior, according to my test, below. Not only are _-prefixed fields visible within a subclass, they are visible within foreign classes as well (unless I don't get what 'visible' means). Also, directly accessing the restricted hash works fine. Where can I find more about the behavior of the fields pragma, short of going at the source code? { package Foo; use strict; use warnings; use fields qw/a _b __c/; sub new { my ( $class ) = @_; my Foo $self = fields::new($class); $self->a = 1; $self->b = 2; $self->c = 3; return $self; } sub a : lvalue { shift->{a} } sub b : lvalue { shift->{_b} } sub c : lvalue { shift->{__c} } } { package Bar; use base 'Foo'; use strict; use warnings; use Data::Dumper; my $o = Bar->new; print Dumper $o; ##$VAR1 = bless({'_b' => 2, '__c' => 3, 'a' => 1}, 'Foo'); $o->a = 4; $o->b = 5; $o->c = 6; print Dumper $o; ##$VAR1 = bless({'_b' => 5, '__c' => 6, 'a' => 4}, 'Foo'); $o->{a} = 7; $o->{_b} = 8; $o->{__c} = 9; print Dumper $o; ##$VAR1 = bless({'_b' => 8, '__c' => 9, 'a' => 7}, 'Foo'); }

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  • In what circumstances are instance variables declared as '_var' in 'use fields' readonly?

    - by Pedro Silva
    I'm trying to understand the behavior of the fields pragma, which I find poorly documented, regarding fields prefixed with underscores. This is what the documentation has to say about it: Field names that start with an underscore character are made private to the class and are not visible to subclasses. Inherited fields can be overridden but will generate a warning if used together with the -w switch. This is not consistent with its actual behavior, according to my test, below. Not only are _-prefixed fields visible within a subclass, they are visible within foreign classes as well (unless I don't get what 'visible' means). Also, directly accessing the restricted hash works fine. Where can I find more about the behavior of the fields pragma, short of going at the source code? { package Foo; use strict; use warnings; use fields qw/a _b __c/; sub new { my ( $class ) = @_; my Foo $self = fields::new($class); $self->a = 1; $self->b = 2; $self->c = 3; return $self; } sub a : lvalue { shift->{a} } sub b : lvalue { shift->{_b} } sub c : lvalue { shift->{__c} } } { package Bar; use base 'Foo'; use strict; use warnings; use Data::Dumper; my $o = Bar->new; print Dumper $o; ##$VAR1 = bless({'_b' => 2, '__c' => 3, 'a' => 1}, 'Foo'); $o->a = 4; $o->b = 5; $o->c = 6; print Dumper $o; ##$VAR1 = bless({'_b' => 5, '__c' => 6, 'a' => 4}, 'Foo'); $o->{a} = 7; $o->{_b} = 8; $o->{__c} = 9; print Dumper $o; ##$VAR1 = bless({'_b' => 8, '__c' => 9, 'a' => 7}, 'Foo'); }

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  • Inserting variables into a query string - it won't work!

    - by Jonesy
    Basically i have a query string that when i hardcode in the catalogue value its fine. when I try adding it via a variable it just doesn't pick it up. This works: Dim WaspConnection As New SqlConnection("Data Source=JURA;Initial Catalog=WaspTrackAsset_NROI;User id=" & ConfigurationManager.AppSettings("WASPDBUserName") & ";Password='" & ConfigurationManager.AppSettings("WASPDBPassword").ToString & "';") This doesn't: Public Sub GetWASPAcr() connection.Open() Dim dt As New DataTable() Dim username As String = HttpContext.Current.User.Identity.Name Dim sqlCmd As New SqlCommand("SELECT WASPDatabase FROM dbo.aspnet_Users WHERE UserName = '" & username & "'", connection) Dim sqlDa As New SqlDataAdapter(sqlCmd) sqlDa.Fill(dt) If dt.Rows.Count > 0 Then For i As Integer = 0 To dt.Rows.Count - 1 If dt.Rows(i)("WASPDatabase") Is DBNull.Value Then WASP = "" Else WASP = "WaspTrackAsset_" + dt.Rows(i)("WASPDatabase") End If Next End If connection.Close() End Sub Dim WaspConnection As New SqlConnection("Data Source=JURA;Initial Catalog=" & WASP & ";User id=" & ConfigurationManager.AppSettings("WASPDBUserName") & ";Password='" & ConfigurationManager.AppSettings("WASPDBPassword").ToString & "';") When I debug the catalog is empty in the query string but the WASP variable holds the value "WaspTrackAsset_NROI" Any idea's why? Cheers, jonesy

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  • Who use class variables in SOAP calls with Savon?

    - by Steffen Roller
    I'm writing a little client using Ruby and Savon. The interface changed significantly from version 0.7 to 0.8.x. All my calls don't work anymore :-(. How can I pass on a local member variable. Please see the example, @userName and @userPassword are not defined within the block. begin @response = @authentication_svc.request :wsdl, "AuthenticateUser" do http.headers["SOAPAction"] = "AuthenticateUser" soap.body = "#{@userName}#{@passwd}" end rescue Savon::SOAP::Fault = e @last_soap_error = e.message end

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  • How can I avoid mutable variables in Scala when using ZipInputStreams and ZipOutpuStreams?

    - by pr1001
    I'm trying to read a zip file, check that it has some required files, and then write all valid files out to another zip file. The basic introduction to java.util.zip has a lot of Java-isms and I'd love to make my code more Scala-native. Specifically, I'd like to avoid the use of vars. Here's what I have: val fos = new FileOutputStream("new.zip"); val zipOut = new ZipOutputStream(new BufferedOutputStream(fos)); while (zipIn.available == 1) { val entry = zipIn.getNextEntry if (entryIsValid(entry)) { val fos = new FileOutputStream("subdir/" + entry.getName()); val dest = new BufferedOutputStream(fos); // read data into the data Array var data: Array[Byte] = null var count = zip.read(data) while (count != -1) { dest.write(data, 0, count) count = zip.read(data) } dest.flush dest.close } }

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  • What is the most effective way to create BigInteger instance from int value?

    - by Roman
    I have a method (in 3rd-party library) with BigInteger parameter: public void setValue (BigInteger value) { ... } I don't need 'all its power', I only need to work with integers. So, how can I pass integers to this method? My solution is to get string value from int value and then create BigInteger from string: int i = 123; setValue (new BigInteger ("" + i)); Are there any other (recommended) ways to do that?

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  • Is it good practice to name variables differently when defining more than one function?

    - by John
    For example, in this simple function where fun1 takes as input two numbers, adds them together and passes them to function 2 for printing the output. var1_in is local to each function, so is it OK to use the name var1_in in both functions, or is it better practice to call them different things? fun1 <- function (var1_in, var2_in) { var3 = var1_in + var2_in fun2(var3) } fun2 <- function (var1_in) { var4 = var1_in print(var4) }

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  • How can I retrieve the instance of an attribute's associated object?

    - by Brandon Linton
    I'm writing a PropertiesMustMatch validation attribute that can take a string property name as a parameter. I'd like it to find the corresponding property by name on that object and do a basic equality comparison. What's the best way to access this through reflection? Also, I checked out the Validation application block in the Enterprise Library and decided its PropertyComparisonValidator was way too intense for what we need.

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  • Is there a way to prevent an ASP.Net webapp from clearing out page variables on VB side?

    - by Chapso
    I have a webapp in ASP.Net with a VB codebehind. I need a List variable I have declared to persist as long as the person is on the page, but currently any time a control posts back to the code, everything is cleared out. I am completely new to ASP.net, so I have no idea if this is even possible. Can it be done with a Session variable? Those seem to me to be limited to base types, but I could be wrong.

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  • Visual Studio 2008\Backup Files folder created when every new VS instance is opened.

    - by Lukasz Podolak
    Hi, I think I have something broken with the path that VS 2008 saves the backup files. Since few days, it creates a new "Visual Studio 2008" directory in the same folder that my .sln file exists. Then, after the time of the first auto-save expires, the backup files are being saved to this folder. I browsed the tools-options dialog but I haven't found a way to set the directory to by static: C:\documents and setings\\My Documents\Visual Studio 2008\Backup Files. Can anybody point me with the right solution to this problem (probably the correct registry entry - I guess) ? thanks

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  • Instance where embedded C++ compilers don't support multiple inheritance?

    - by Nathan
    I read a bit about a previous attempt to make a C++ standard for embedded platforms where they specifically said multiple inheritance was bad and thus not supported. From what I understand, this was never implemented as a mainstream thing and most embedded C++ compilers support most standard C++ constructs. Are there cases where a compiler on a current embedded platform (i.e. something not more than a few years old) absolutely does not support multiple inheritance? I don't really want to do multiple inheritance in a sense where I have a child with two full implementations of a class. What I am most interested in is inheriting from a single implementation of a class and then also inheriting one or more pure virtual classes as interfaces only. This is roughly equivalent to Java/.Net where I can extend only one class but implement as many interfaces as I need. In C++ this is all done through multiple inheritance rather than being able to specifically define an interface and declare a class implements it.

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  • How to get to the key name of a referenced entity property from an entity instance without a datastore read in google app engine?

    - by Sumeet Pareek
    Consider I have the following models - class Team(db.Model): # say I have just 5 teams name = db.StringProperty() class Player(db.Model): # say I have thousands of players name = db.StringProperty() team = db.ReferenceProperty(Team, collection_name="player_set") Key name for each Team entity = 'team_' , and for each Player entity = 'player_' By some prior arrangement I have a Team entity's (key_name, name) mapping available to me. For example (team_01, United States Of America), (team_02, Russia) etc I have to show all the players and their teams on a page. One way of doing this would be - players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(player.team.name) #This is a total of 1x1000 = 1000 DB reads That is a 1001 DB reads for a silly thing. The interesting part is that when I do a db.to_dict() on players, it shows that for every player in that list there is 'name' of the player and there is the 'key_name' of the team available too. So how can I do the below ?? players = Player.all().fetch(1000) # This is 1 DB read for player in players: # This will iterate 1000 times self.response.out.write(player.name) # This is obviously not a DB read self.response.out.write(team_list[player.<SOME WAY OF GETTING TEAM KEY NAME>]) # Here 'team_list' already has (key_name, name) for all 5 teams I have been struggling with this for a long time. Have read every available documentation. I could just hug the person that can help me here :-) Disclaimer: The above problem description is not a real scenario. It is a simplified arrangement that represents my problem exactly. I have run into it in a rater complex and big GAE appication.

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  • Why can't I access the instance.__class__ attribute in Python?

    - by froadie
    I'm new to Python, and I know I must be missing something pretty simple, but why doesn't this very, very simple code work? class myClass: pass testObject = myClass print testObject.__class__ I get the following error: AttributeError: class myClass has no attribute '__class__' Doesn't every object in Python have a __class__ attribute?

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  • Should I cast variables that use a typdef'd type?

    - by mesorismo
    If I have something like: typedef int MyType; is it good practice to cast the operands of an operation if I do something like this: int x = 5; int y = 6; MyType a = (MyType)(x + y); I know that I don't need to do that but wondering if it's better for intent/documentation/readability concerns.

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  • How do I split up a long value (32 bits) into four char variables (8bits) using C?

    - by Jordan S
    I have a 32 bit long variable, CurrentPosition, that I want to split up into 4, 8bit characters. How would I do that most efficiently in C? I am working with an 8bit MCU, 8051 architectecture. unsigned long CurrentPosition = 7654321; unsigned char CP1 = 0; unsigned char CP2 = 0; unsigned char CP3 = 0; unsigned char CP4 = 0; // What do I do next? Should I just reference the starting address of CurrentPosition with a pointer and then add 8 two that address four times? It is little Endian. ALSO I want CurrentPosition to remain unchanged.

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  • ASP.Net MVC 2 is it possible to get the same instance of model(with slight changes) in HttpPost meth

    - by jjjjj
    Hi I have a complex entity User: public class User : BaseEntity { public virtual Taxi Taxi { get; set; } --> That is why i call it "complex" public virtual string Login { get; set; } public virtual string Password { get; set; } } where Taxi is a parent of User (Taxi has-many Users): public class Taxi : BaseEntity { public virtual string Name { get; set; } public virtual string ClientIp { get; set; } } BaseEntity consists of public virtual int Id { get; private set; } The problem occurs while trying to edit User [Authorize] public ActionResult ChangeAccountInfo() { var user = UserRepository.GetUser(User.Identity.Name); return View(user); } My ChangeAccountInfo.aspx <fieldset> <legend>Fields</legend> <% %> <div class="editor-label"> <%: Html.LabelFor(model => model.Login) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.Login) %> <%: Html.ValidationMessageFor(model => model.Login) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.Password) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.Password) %> <%: Html.ValidationMessageFor(model => model.Password) %> </div> <div class="editor-field"> <%: Html.HiddenFor(model => model.Taxi.Name)%> </div> <p> <input type="submit" value="Save" /> </p> </fieldset> Post changes: [Authorize] [HttpPost] public ActionResult ChangeAccountInfo(User model) { if (ModelState.IsValid) { UserRepository.UpdateUser(model); return RedirectToAction("ChangeAccountInfoSuccess", "Account"); } return View(model); } But, the (User model) parameter has User.Id == 0 -- User entity had 5 before edit User.Login == "my new login" User.Password == "my new password" User.Taxi.Id == 0 -- User.Taxi entity had 3 before edit User.Taxi.Name == "old hidden name" User.Taxi.ClientIp == null -- User entity had 192.168.0.1 before edit Q: Is it possible not to mark all the fields of an entity (that should be in my UpdateUser) with tag "hidden" but still have them unchanged in my HttpPost method? e.g. not User.Taxi.ClientIp = null, but User.Taxi.ClientIp = 192.168.0.1 I'm using nhibernate, if it matters.

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  • How to get session variables from php server with Ajax function? (PHP HTML JS Ajax)

    - by Ole Jak
    so in my php I have something like this $_SESSION['opened'] = true; But It will not be set to true until user will perform some actions with some other html\php pages So I need on some Ajax function to be able get this session variable. And some PHP sample of function to get variable in form ready for Ajax to get it. so I need something to AJAX requesting to an action (to some simple php code) which will return a value from $_SESSION. How to do such thing?

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  • Object reference not set to an instance of an object.....?

    - by jamal
    Hi guys I always got this error from my site and it keeps bugging me.I've been trying to figure out the cause of this error but I can't really figure it out. Here's the stacktrace: at BasePage.Page_PreInit(Object sender, EventArgs e) at System.EventHandler.Invoke(Object sender, EventArgs e) at System.Web.UI.Page.OnPreInit(EventArgs e) at System.Web.UI.Page.PerformPreInit() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) And on my basepage I only got this code: Imports Microsoft.VisualBasic Public Class BasePage Inherits System.Web.UI.Page Private Sub Page_PreInit(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreInit Page.Theme = "Something" If (Request.UserAgent.IndexOf("AppleWebKit") 0) Then Request.Browser.Adapters.Clear() End If End Sub Private Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender If Me.Title = "Untitled Page" Then Throw New Exception("Page title cannot be ""Untitled Page"".") End If End Sub End Class According to the stacktrace this always happens on my basepage preinit event.What do you think is the problem here guys?

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  • How do I check if an instance has an object to skip displaying the values?

    - by Angela
    I have created a polymorphic association around a model called status. Some contacts will have a status associated with it. Many won't. If I try to call a status when one is not there, I get an error. Right now, even if I haven't created a status for the model, it still runs whatever is in the if-end block. Here's what I am trying, but it's not working: <% if [email protected]? %> <p>Status: <%= @status.find(:last).status %></p> <% end %> In the controller, it is defined below: @status = Contact.find(@contact).statuses By the way, also open to make code more readable and DRY.

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