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• Doubly Linked Lists Implementation

  - by user552127

  Hi All, I have looked at most threads here about Doubly linked lists but still unclear about the following. I am practicing the Goodrich and Tamassia book in Java. About doubly linked lists, please correct me if I am wrong, it is different from a singly linked list in that a node could be inserted anywhere, not just after the head or after the tail using both the next and prev nodes available, while in singly linked lists, this insertion anywhere in the list is not possible ? If one wants to insert a node in a doubly linked list, then the default argument should be either the node after the to-be inserted node or node before the to-be inserted node ? But if this is so, then I don't understand how to pass the node before or after. Should we be displaying all nodes that were inserted till now and ask the user to select the node before or after which some new node is to be inserted ? My doubt is how to pass this default node. Because I assume that will require the next and prev nodes of these nodes as well. For e.g, Head<-A<-B<-C<-D<-E<-tail If Z is the new node to be inserted after say D, then how should node D be passed ? I am confused with this though it seems pretty simple to most. But pl do explain. Thanks, Sanjay

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• Need a refresher course on property access...

  - by Code Sherpa

  Hi. I need help with accessing class properties within a given class. For example, take the below class: public partial class Account { private Profile _profile; private Email _email; private HostInfo _hostInfo; public Profile Profile { get { return _profile; } set { _profile = value; } } public Email Email { get { return _email; } set { _email = value; } } public HostInfo HostInfo { get { return _hostInfo; } set { _hostInfo = value; } } In the class "Account" exists a bunch of class properties such as Email or Profile. Now, when I want to access those properties at run-time, I do something like this (for Email): _accountRepository = ObjectFactory.GetInstance<IAccountRepository>(); string username = Cryptography.Decrypt(_webContext.UserNameToVerify, "verify"); Account account = _accountRepository.GetAccountByUserName(username); if(account != null) { account.Email.IsConfirmed = true; But, I get "Object reference not set..." for account.Email... Why is that? How do I access Account such that account.Email, account.Profile, and so on returns the correct data for a given AccountId or UserName. Here is a method that returns Account: public Account GetAccountByUserName(string userName) { Account account = null; using (MyDataContext dc = _conn.GetContext()) { try { account = (from a in dc.Accounts where a.UserName == userName select a).FirstOrDefault(); } catch { //oops } } return account; } The above works but when I try: account = (from a in dc.Accounts join em in dc.Emails on a.AccountId equals em.AccountId join p in dc.Profiles on em.AccountId equals p.AccountId where a.UserName == userName select a).FirstOrDefault(); I am still getting object reference exceptions for my Email and Profile properties. Is this simply a SQL problem or is there something else I need to be doing to be able to fully access all the properties within my Account class? Thanks!

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• How to handle window closed in the middle of a long running operation gracefully?

  - by Marek

  We have the following method called directly from the UI thread: void DoLengthyProcessing() { DoStuff(); var items = DoMoreStuff(); //do even more stuff - 200 lines of code trimmed this.someControl.PrepareForBigThing(); //someControl is a big user control //additional 100 lines of code that access this.someControl this.someControl.Finish(items); } Many of the called methods call Application.DoEvents() (and they do so many times) (do not ask me why, this is black magic written by black magic programmers and it can not be changed because everyone is scared what the impact would be) and there is also an operation running on a background thread involved in the processing. As a result, the window is not fully nonresponsive and can be closed manually during the processing. The Dispose method of the form "releases" the someControl variable by setting it to null. As a result, in case the user closes the window during the lengthy process, a null reference exception is thrown. How to handle this gracefully without just catching and logging the exception caused by disposal? Assigning the someControl instance to a temporary variable in the beginning of the method - but the control contains many subcontrols with similar disposal scheme - sets them to null and this causes null reference exceptions in other place put if (this.IsDisposed) return; calls before every access of the someControl variable. - making the already nasty long method even longer and unreadable. in Closing event, just indicate that we should close and only hide the window. Dispose it at the end of the lengthy operation. This is not very viable because there are many other methods involved (think 20K LOC for a single control) that would need to handle this mechanism as well. How to most effectively handle window disposal (by user action) in the middle of this kind of processing?

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• Rendering maps from raw SVG data in Java

  - by Lunikon

  In an application of mine I have to display locations and great circle paths in a map which is rendered to PNG and then displayed on the web. For this I simply use a world map (NASA's Blue Marbel in fact) scaled to various "zoom levels" as base image and only display the a part of it matching the final image size and fitting all items to be displayed. Straight forward so far. Now I came across Wikipedia's awesome blank SVG maps which contain all the country codes for easy reference and I was wondering whether it was possible to use those to have more customized colors and to highliht countries etc. So I did a bit of googling and was looking for Java libraries which would enable me to load the blank SVG map to memory allows for easy reference/selection of certain paths do manipulations of coloring, stroke widths etc render to a buffered image as the background for the great-circle paths/nodes What I came across quite often was Batik, but it looks like a really heavy framework and I'm not quite sure whether it is what I'm looking for. I have recently played around with Raphaël a bit and I like the way it handles working with vector graphics in code. If the Java framework for my purpose would feature a similar interface, that would be a nice-to-have. Any recommendations what toolset would be approriate for my purposes?

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• Inversion of control domain objects construction problem

  - by Andrey

  Hello! As I understand IoC-container is helpful in creation of application-level objects like services and factories. But domain-level objects should be created manually. Spring's manual tells us: "Typically one does not configure fine-grained domain objects in the container, because it is usually the responsibility of DAOs and business logic to create/load domain objects." Well. But what if my domain "fine-grained" object depends on some application-level object. For example I have an UserViewer(User user, UserConstants constants) class. There user is domain object which cannot be injected, but UserViewer also needs UserConstants which is high-level object injected by IoC-container. I want to inject UserConstants from the IoC-container, but I also need a transient runtime parameter User here. What is wrong with the design? Thanks in advance! UPDATE It seems I was not precise enough with my question. What I really need is an example how to do this: create instance of class UserViewer(User user, UserService service), where user is passed as the parameter and service is injected from IoC. If I inject UserViewer viewer then how do I pass user to it? If I create UserViewer viewer manually then how do I pass service to it?

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• Is there a general-purpose printf-ish routine defined in any C standard

  - by supercat

  In many C libraries, there is a printf-style routine which is something like the following: int __vgprintf(void *info, (void)(*print_function(void*, char)), const char *format, va_list params); which will format the supplied string and call print_function with the passed-in info value and each character in sequence. A function like fprintf will pass __vgprintf the passed-in file parameter and a pointer to a function which will cast its void* to a FILE* and output the passed-in character to that file. A function like snprintf will create a struct holding a char* and length, and pass the address of that struct to a function which will output each character in sequence, space permitting. Is there any standard for such a function, which could be used if e.g. one wanted a function to output an arbitrary format to a TCP port? A common approach is to allocate a buffer one hopes is big enough, use snprintf to put the data there, and then output the data from the buffer. It would seem cleaner, though, if there were a standard way to to specify that the print formatter should call a user-supplied routine with each character.

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• How can I make one Maven module depend on another?

  - by Daniel Pryden

  OK, I thought I understood how to use Maven... I have a master project M which has sub-projects A, B, and C. C contains some common functionality (interfaces mainly) which is needed by A and B. I can run mvn compile jar:jar from the project root directory (the M directory) and get JAR files A.jar, B.jar, and C.jar. (The versions for all these artifacts are currently 2.0-SNAPSHOT.) The master pom.xml file in the M directory lists C under its <dependencyManagement> tag, so that A and B can reference C by just including a reference, like so: <dependency> <groupId>my.project</groupId> <artifactId>C</artifactId> </dependency> So far, so good. I can run mvn compile from the command line and everything works fine. But when I open the project in NetBeans, it complains with the problem: "Some dependency artifacts are not in the local repository", and it says the missing artifact is C. Likewise from the command line, if I change into the A or B directories and try to run mvn compile I get "Build Error: Failed to resolve artifact." I expect I could manually go to where my C.jar was built and run mvn install:install-file, but I'd rather find a solution that enables me to just work directly in NetBeans (and/or in Eclipse using m2eclipse). What am I doing wrong?

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• How to make a Stored Procedure that takes in XML and uses that xml as an Update + call this stored p

  - by chobo2

  Hi I am using ms sql server 2005 and I want to do a mass update. I am thinking that I might be able to do it with sending an xml document to a stored procedure. So I seen many examples on how to do it for insert CREATE PROCEDURE [dbo].[spTEST_InsertXMLTEST_TEST](@UpdatedProdData XML) AS INSERT INTO dbo.UserTable(CreateDate) SELECT @UpdatedProdData.value('(/ArrayOfUserTable/UserTable/CreateDate)[1]', 'DATETIME') But I am not sure how it would look like for an update. I am also unsure how do I pass in the xml through ado.net? Do I pass it as a string through a parameter or what? I know sqlDataApater has a batch update method but I am using linq to sql. So I rather keep using it. So if this works I would be able to grab all records with linq to sql and have them as objects. Then manipulate the objects and use xml seralization. Finally I could just use ado.net simple to send the xml to the server. This might be slower then the sqlDataAdapter but I am willing to take that hit if I can keep using objects.

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• Async task ASP.net HttpContext.Current.Items is empty - How do handle this?

  - by GuruC

  We are running a very large web application in asp.net MVC .NET 4.0. Recently we had an audit done and the performance team says that there were a lot of null reference exceptions. So I started investigating it from the dumps and event viewer. My understanding was as follows: We are using Asyn Tasks in our controllers. We rely on HttpContext.Current.Items hashtable to store a lot of Application level values. Task<Articles>.Factory.StartNew(() => { System.Web.HttpContext.Current = ControllerContext.HttpContext.ApplicationInstance.Context; var service = new ArticlesService(page); return service.GetArticles(); }).ContinueWith(t => SetResult(t, "articles")); So we are copying the context object onto the new thread that is spawned from Task factory. This context.Items is used again in the thread wherever necessary. Say for ex: public class SomeClass { internal static int StreamID { get { if (HttpContext.Current != null) { return (int)HttpContext.Current.Items["StreamID"]; } else { return DEFAULT_STREAM_ID; } } } This runs fine as long as number of parallel requests are optimal. My questions are as follows: 1. When the load is more and there are too many parallel requests, I notice that HttpContext.Current.Items is empty. I am not able to figure out a reason for this and this causes all the null reference exceptions. 2. How do we make sure it is not null ? Any workaround if present ? NOTE: I read through in StackOverflow and people have questions like HttpContext.Current is null - but in my case it is not null and its empty. I was reading one more article where the author says that sometimes request object is terminated and it may cause problems since dispose is already called on objects. I am doing a copy of Context object - its just a shallow copy and not a deep copy.

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• winUserControl in VS2010 - properties are not visible in designer

  - by mj82

  I have a problem with (I suppose) my Visual Studio 2010 Express environment: when I design my own UserControl, in Properties grid I can't see public properties of that control. They are however visible in the project, that reference this control. As it's Express Edition, I create new empty project, then add new UserControl to it. Then, for a test, I put following code: using System; using System.Collections.Generic; using System.ComponentModel; using System.Drawing; using System.Data; using System.Linq; using System.Text; using System.Windows.Forms; namespace Project1 { public partial class UserControl1 : UserControl { private int myNumber; [Browsable(true)] public int MyNumber { get { return myNumber; } set { myNumber = value; } } public UserControl1() { InitializeComponent(); } } } In VS 2008, as I remember, that should be enogh to show MyNumber property in Properties grid, even without [Browsable(true)] attribute. In VS 2010 however, when I double click UserControl1.cs in Solution Explorer and look in Properties, I don't see MyNumber. When I reference and use this control in another project, there is an access to it's properties. I've tried to competly reinstall VS 2010 environment, including SP1, but with no success. Do you have any idea what can be wrong? By the way: none of these attributes are working, either: [Browsable(true)] [EditorBrowsable(EditorBrowsableState.Always)] [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)] [Bindable(true)] Best regards, Marcin

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• Tracking down slow managed DLL loading

  - by Alex K

  I am faced with the following issue and at this point I feel like I'm severely lacking some sort of tool, I just don't know what that tool is, or what exactly it should be doing. Here is the setup: I have a 3rd party DLL that has to be registered in GAC. This all works fine and good on pretty much every machine our software was deployed on before. But now we got 2 machines, seemingly identical to the ones we know work (they are cloned from the same image and stuffed with the same hardware, so pretty much the only difference is software settings, over which I went over and over, and they seem fine). Now the problem, the DLL in GAC takes a very long time to load. At least I believe this is the issue, what I can say definitively is that instantiating a single class from that DLL is the slow part. Once it is loaded, thing fly as they always have. But while on known-good machines the DLL loads so fast that a timestamp in the log doesn't even change, on these 2 machines it take over 1min to load. Knowns: I have no access to the source, so I can't debug through the DLL. Our app is the only one that uses it (so shouldn't be simultaneous access issues). There is only one version of this DLL in existance, so it shouldn't be a matter of version conflict. The GAC reference is being used (if I uninstall the DLL from GAC, an exception will be thrown about the missing GAC reference). Could someone with a greater skill in debug-fu suggest what I can do to track down the root cause of this issue?

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• what is the best practice approach for n-tier application development with entity framework?

  - by samsur

  I am building an application using entity framework. I am using the T4 template to generate self tracking entities. Currently, I am thinking of creating the entity framework code in a separate project. In this same project, I would have partial classes with additional methods for the entities. I am thinking of creating a separate project for a service layer (WCF) with methods for the upper/presentation tier. The WCF layer will reference the entity framework project. The methods in the WCF layer will return the entities or accept the entities as the parameters. I am thinkg of creating a third project for the presentation layer (ASP.net), this will make calls to the WCF service but will also need to reference the entities as the WCF methods take these types as the parameters/return types. In short, i want to use the STE entities generated by the T4 template as a DTO to be used in all layers. I was originally thinking of creating a business logic layer that maps to each entities. Example: If i have a customer class, the Business Layer would have a CustomerBLL class and then methods in the customerBLL will be used by the service layer. I was also trying to create a DTO in this business layer. I however found that this approach is very time consuming and i do not see a major benefit as it would create more maintenance work. What is the best practice for n-tier application development using entity framework 4?

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• [jQuery] What would be the best way to perform a basic CRUD using AJAX

  - by rasouza

  I'm having trouble to make a simple CRUD in my site. I have a table of registries <table> <tbody> <?php foreach ($row as $reg) { ?> <tr <?php if ($reg['value'] < 0) { echo "class='error'"; } ?>> <td><?php echo $reg['creditor'] ?></td> <td><?php echo $reg['debtor'] ?></td> <td><?php echo $reg['reason'] ?></td> <td>R$ <?php echo number_format(abs($reg['value']), 2, ',', ' ')?></td> <td><a **href="<?php echo $this->baseUrl(); ?>/history/delete/id/<?php echo $reg['id']; ?>"** class="delete"><img src="http://192.168.0.102/libraries/css/blueprint/plugins/buttons/icons/cross.png" alt=""/></a></td> </tr> <?php } ?> </tbody> </table> which I would like to perform a simple delete in these rows using AJAX (preferenciably with jQuery). The question is: do I have to create a function in JS and add onmouseclick event in the HTML? is there a more consistent way for doing this, like adding $('.delete').click() directly in the js file? If so, how do I pass the row ID for the ajax function? What I really want is to know how to pass the row ID to $.ajax() jQuery function through a clean! way

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• get the javascript variable value to Code Behind Asp.net

  - by Siddiq Baig

  i am trying to pass the javascript variable value to hidden feild from code behind by onclientclick event.. i have button that have both client and server side onclick event <asp:Button ID="btnSave" runat="server" Text="Save" class="buttonstyle" onclick="btnSave_Click" OnClientClick="otherdata()" /> i want to get the javascript value in codebehind from OnClientClick event and then want to insert that value to database table from Onclick event function otherdata() { var hv = $('input[id$=hdnOthers]').val(); var $arrT = $('#<%=gv_Others.ClientID %>').find('input:text[id$="txtEmp"]'); var count = []; for (var i = 0; i < 10; i++) { var $txt = $arrT[i]; count[i] = $($txt).val(); } hv = count; alert(hv); } i am getting the value in alert and assigning the value to hidden field but problem is that i am not getting the value in hidden field from code behind.. although i have already pass the value to hidden field from javascript so why i am not getting that value from code behind.. protected void Insert_OtherServices() { dsJobCardTableAdapters.Select_OtherServiceTableAdapter dsother = new dsJobCardTableAdapters.Select_OtherServiceTableAdapter(); string hdn = hdnOthers.Value; dsother.Insert_OtherService(hdn); }

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• using asp.net membership provider in a dll

  - by Keith Barrows

  I've used Membership Providers in web apps over the last several years. I now have a new "request" for an internal project at work. They would like a service (not a web service) to do a quick authenticate against. Basically, exposing the ValidateUser(UserName, Password) method... I am building this in a DLL that will sit with our internal web site. What is the best approach to make this work? The DLL will not reference the web app and the web app will reference the DLL. How do I make the DLL aware of the Membership Provider? TIA PS: If this has been answered elsewhere please direct me to that... EDIT: I found an article on using ASP.NET Membership with WinForms and/or WPF applications. Unfortunately, these depend on an app.config file. A DLL appears to not use the app.config once published. If I am wrong, please set me straight! The article is here: http://aspalliance.com/1595_Client_Application_Services__Part_1.all

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• Cant we use a Set or collection as a return type in GAE?

  - by user273422

  In my code i have used Set<Employees> as a return type to my function addEmp(). So, i m gettin an Compilation error. The Error is: Compiling module com.employeedepartmentgae.Employeedepartmentgae Refreshing module from source Validating newly compiled units Removing units with errors [ERROR] Errors in 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingServiceAsync.java' [ERROR] Line 6: The import com.employeedepartmentgae.server.domainobject.Employee cannot be resolved [ERROR] Line 18: Employee cannot be resolved to a type [ERROR] Errors in 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingService.java' [ERROR] Line 6: The import com.employeedepartmentgae.server.domainobject.Employee cannot be resolved [ERROR] Line 20: Employee cannot be resolved to a type [ERROR] Errors in 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/EmployeeWidget.java' [ERROR] Line 12: The import com.employeedepartmentgae.server.domainobject.Employee cannot be resolved [ERROR] Line 75: The method addEmp(String, String, String, AsyncCallback) from the type GreetingServiceAsync refers to the missing type Employee [ERROR] Line 75: The type new AsyncCallback(){} must implement the inherited abstract method AsyncCallback.onSuccess(Set) [ERROR] Line 75: Employee cannot be resolved to a type [ERROR] Line 94: The method onSuccess(Set) of type new AsyncCallback(){} must override or implement a supertype method [ERROR] Line 94: Employee cannot be resolved to a type [ERROR] Line 96: Employee cannot be resolved to a type [ERROR] Line 96: Employee cannot be resolved to a type [ERROR] Line 98: Employee cannot be resolved to a type Removing invalidated units [WARN] Compilation unit 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/Employeedepartmentgae.java' is removed due to invalid reference(s): [WARN] file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/EmployeeWidget.java [WARN] Compilation unit 'file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/DepartmentWidget.java' is removed due to invalid reference(s): [WARN] file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingService.java [WARN] file:/home/wissen18/employeedepartmentgae/src/com/employeedepartmentgae/client/GreetingServiceAsync.java Computing all possible rebind results for 'com.employeedepartmentgae.client.Employeedepartmentgae' Rebinding com.employeedepartmentgae.client.Employeedepartmentgae Checking rule [ERROR] Unable to find type 'com.employeedepartmentgae.client.Employeedepartmentgae' [ERROR] Hint: Previous compiler errors may have made this type unavailable [ERROR] Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly So please help me.....

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• Passing session between jsf backing bean and model

  - by Rachel

  Background : I am having backing bean which has upload method that listen when file is uploaded. Now I pass this file to parser and in parser am doing validation check for row present in csv file. If validation fails, I have to log information and saving in logging table in database. My end goal : Is to get session information in logging bean so that I can get initialContext and make call to ejb to save data to database. What is happening : In my upload backing bean, am getting session but when i call parser, I do not pass session information as I do not want parser to be dependent on session as I want to unit test parser individually. So in my parser, I do not have session information, from parser am making call to logging bean(just a bean with some ejb methods) but in this logging bean, i need session because i need to get initial context. Question Is there a way in JSF, that I can get the session in my logging bean that I have in my upload backing bean? I tried doing: FacesContext ctx = FacesContext.getCurrentInstance(); HttpSession session = (HttpSession) ctx.getExternalContext().getSession(false); but session value was null, more generic question would be : How can I get session information in model bean or other beans that are referenced from backing beans in which we have session? Do we have generic method in jsf using which we can access session information throughout JSF Application?

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• Packages name conflicting with getters and setters?

  - by MrKishi

  Hello, folks. So, I've came across this compilation error a while ago.. As there's an easy fix and I didn't find anything relevant at the time, I eventually let it go. I just remembered it and I'm now wondering if this is really part of the language grammar (which I highly doubt) or if it's a compiler bug. I'm being purely curious about this -- it doesn't really affect development, but it would be nice to see if any of you have seen this already. package view { import flash.display.Sprite; public class Main extends Sprite { private var _view:Sprite = new Sprite(); public function Main() { this.test(); } private function test():void { trace(this.view.x, this.view.y); //1178: Attempted access of inaccessible property x through a reference with static type view:Main. //1178: Attempted access of inaccessible property y through a reference with static type view:Main. //Note that I got this due to the package name. //It runs just fine if I rename the package or getter. } public function get view():Sprite { return this._view; } } }

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• MEF instance management

  - by Lawrence A. Contreras

  I am working on application that has multiple modules and sub modules. Here's what I need to do: ModuleA has a sub module SubModuleA, SubModuleB, SubModuleC. I want to export ModuleA, SubModuleA, SubModuleB, SubModuleC. ModuleA can have multiple instances. Whenever I import ModuleA inside the sub modules, I want to get the correct instance and also when I import SubModuleA,SubModuleB and SubModuleC inside other classes. How can I manage that scenario using MEF? Do I really need to use MEF. Updated: Here's a quick example: public class School { List<Classroom> classRooms { get; set; } } [Export] public class Classroom { List<Teacher> teachers { get; set; } } public class Teacher { List<Student> students { get; set; } } public class Student { [Import] Classroom classroom { get; set; } } As you can see, I want to export the classroom class because I need to import it in the Student class, let's just say that I really need the classroom class inside the student class. I want to skip the part where we pass the classroom to the teacher and from the teacher we'll pass it to the student. But when I import classroom, I want to have the correct instance where that class room contains the teacher of the student.

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• odd behavior with C# ftp client class

  - by geoff

  I found an ftp client class in c# over a year ago and have been using it in a process that uploads files on a nightly basis. A few days ago we started having a problem where it would time out. I'm not well versed in this so I'm not sure why it's doing this. When the program starts uploading a file it checks to see if it's logged in and if not, it calls the login method. In that method is this block of code. if (this.resultCode != 230) { this.sendCommand("PASS " + password); if (!(this.resultCode == 230 || this.resultCode == 202)) { this.cleanup(); throw new FtpException(this.result.Substring(4)); } } On the line that says this.sendCommand("PASS"... it goes into this code. private void sendCommand(String command) { if (this.verboseDebugging) Debug.WriteLine(command, "FtpClient"); Byte[] cmdBytes = Encoding.ASCII.GetBytes((command + "\r\n").ToCharArray()); clientSocket.Send(cmdBytes, cmdBytes.Length, 0); this.readResponse(); } If I let the program run, it times out. However if I step through it into the sendCommand method it executes fine. Does anyone know why it would work fine when I step through it? Nothing on our end has changed and I've been told nothing on the client's end has changed so I'm stumped. Thanks.

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• Why does this code sample produce a memory leak?

  - by citronas

  In the university we were given the following code sample and we were being told, that there is a memory leak when running this code. The sample should demonstrate that this is a situation where the garbage collector can't work. As far as my object oriented programming goes, the only codeline able to create a memory leak would be items=Arrays.copyOf(items,2 * size+1); The documentation says, that the elements are copied. Does that mean the reference is copied (and therefore another entry on the heap is created) or the object itself is being copied? As far as I know, Object and therefore Object[] are implemented as a reference type. So assigning a new value to 'items' would allow the garbage collector to find that the old 'item' is no longer referenced and can therefore be collected. In my eyes, this the codesample does not produce a memory leak. Could somebody prove me wrong? =) import java.util.Arrays; public class Foo { private Object[] items; private int size=0; private static final int ISIZE=10; public Foo() { items= new Object[ISIZE]; } public void push(final Object o){ checkSize(); items[size++]=o; } public Object pop(){ if (size==0) throw new ///... return items[--size]; } private void checkSize(){ if (items.length==size){ items=Arrays.copyOf(items,2 * size+1); } } }

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• which is better: a lying copy constructor or a non-standard one?

  - by PaulH

  I have a C++ class that contains a non-copyable handle. The class, however, must have a copy constructor. So, I've implemented one that transfers ownership of the handle to the new object (as below) class Foo { public: Foo() : h_( INVALID_HANDLE_VALUE ) { }; // transfer the handle to the new instance Foo( const Foo& other ) : h_( other.Detach() ) { }; ~Foo() { if( INVALID_HANDLE_VALUE != h_ ) CloseHandle( h_ ); }; // other interesting functions... private: /// disallow assignment const Foo& operator=( const Foo& ); HANDLE Detach() const { HANDLE h = h_; h_ = INVALID_HANDLE_VALUE; return h; }; /// a non-copyable handle mutable HANDLE h_; }; // class Foo My problem is that the standard copy constructor takes a const-reference and I'm modifying that reference. So, I'd like to know which is better (and why): a non-standard copy constructor: Foo( Foo& other ); a copy-constructor that 'lies': Foo( const Foo& other ); Thanks, PaulH

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• jQuery AJAX tabs + PHP

  - by ufw

  Hi, seems like I'm stuck with jQuery tabs. I'm trying to pass selected tab name to some php script but is seems like it doesn't get any data. This is how tabs normally work without any response from server side: http://pastebin.com/KBxj7p5k And this is how I try to pass the the current tab name to the server: $(document).ready(function() { $('ul.tabs li').css('cursor', 'pointer'); $('ul.tabs.tabs1 li').click(function(){ var thisClass = this.className.slice(0,2); $('div.t1').hide(); $('div.t2').hide(); $('div.t3').hide(); $('div.t4').hide(); $('div.' + thisClass).show('fast'); $('ul.tabs.tabs1 li').removeClass('tab-current'); $(this).addClass('tab-current'); var name = thisClass; var data = 'name='+name; $.ajax ({ type:"GET", url:"handler.php", data:data, success:function(html) { thisClass.html(html); } }); }); Thanks.

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• How to marshal an object and its content (also objects)

  - by Waldo Spek

  I have a question for which I suspect the answer is a bit complex. At this moment I am programming a DLL (class library) in C#. This DLL uses a 3rd party library and therefore deals with 3rd party objects of which I do not have the source code. Now I am planning to create another DLL, which is going to be used in a later stadium in my application. This second DLL should use the 3rd party objects (with corresponding object states) created by the first DLL. Luckily the 3rd party objects extend the MarshalByRefObject class. I can marshal the objects using System.Runtime.Remoting.Marshal(...). I then serialize the objects using a BinaryFormatter and store the objects as a byte[] array. All goes well. I can deserialize and unmarshal in a the opposite way and end up with my original 3rd party objects...so it appears... Nevertheless, when calling methods on my 3rd party deserialized objects I get object internal exceptions. Normally these methods return other 3rd party objects, but (obviously - I guess) now these objects are missing because they weren't serialized. Now my global question: how would I go about marshalling/serializing all the objects which my 3rd party objects reference...and cascade down the "reference tree" to obtain a full and complete serialized object? Right now my guess is to preprocess: obtain all the objects and build my own custom object and serialize it. But I'm hoping there is some other way...

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• JavaScript, jQuery, XML - if statement not executing for unknown reason

  - by Jack Roscoe

  Hi, I have a 'for' loop which extracts data from an XML document and adds it into some JavaScript objects, each time the loop executes I want it to run a certain function depending on the value of the attribute 'typ' which is being retrieved from the xml. Currently, the data from the XML is successfully being parsed, which is proven by the first 'alert' you can see which produces the correct value. However, neither of the 'alert' lines in the 'if' statement lower down are being executed and as a result I cannot test the 'ctyp3' function which is supposed to be called. Where have I gone wrong? for (j=0; j<arrayIds.length; j++) { $(xml).find("C[ID='" + arrayIds[j] + "']").each(function(){ // pass values questions[j] = { typ: $(this).attr('typ'), width: $(this).find("I").attr('wid'), height: $(this).find("I").attr('hei'), x: $(this).find("I").attr('x'), y: $(this).find("I").attr('x'), baC: $(this).find("I").attr('baC'), boC: $(this).find("I").attr('boC'), boW: $(this).find("I").attr('boW') } alert($(this).attr('typ')); if ($(this).attr('typ') == '3') { ctyp3(x,y,width,height,baC); alert('pass'); } else { // Add here alert('fail'); } }); }

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