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  • How to implement an abstract class in ruby?

    - by Chirantan
    I know there is no concept of abstract class in ruby. But if at all it needs to be implemented, how to go about it? I tried something like... class A def self.new raise 'Doh! You are trying to instantiate an abstract class!' end end class B < A ... ... end But when I try to instantiate B, it is internally going to call A.new which is going to raise the exception. Also, modules cannot be instantiated but they cannot be inherited too. making the new method private will also not work. Any pointers?

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  • Adding a decorator that converts strings to lowercase in Python

    - by user2905382
    So I am new to learning decorators and I have gone through countless tutorials and while I understand and can mostly follow all of the examples, I think the best way to learn, would be to implement a decorator myself. So I am going to use this example below. I realize a decorator is not at all necessary to do this, but for the sake of learning, I would like to add a decorator that filters the strings like dog name and breed and turns them into lowercase. Any ideas or pointers in the right direction would be appreciated. class Dogs: totalDogs = 0 dogList=[] def __init__(self, breed, color, age): self.breed=breed self.color=color self.age=age Dogs.dogList.append(self.breed) Dogs.totalDogs += 1 def displayDogs(self): print "breed: ", self.breed print "color: ",self.color print "age: ",self.age print "list of breeds:", Dogs.dogList print "total dogs: ", Dogs.totalDogs def somedecorator(*args): #now what terrier=Dogs("TeRrIer", "white", 5) terrier.displayDogs() retriever=Dogs("goldenRETRIEVER", "brown", 10) retriever.displayDogs()

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  • Creating a C++ DLL and then using it in C#

    - by Major
    Ok I'm trying to make a C++ DLL that I can then call and reference in a c# App. I've already made a simple dll using the numberous guides out there, however when I try to reference it in the C# app I get the error Unable to load DLL 'SDES.dll': The specified module could not be found. The code for the program is as follows (bear with me I'm going to include all the files) //These are the DLL Files. ifndef TestDLL_H define TestDLL_H extern "C" { // Returns a + b __declspec(dllexport) double Add(double a, double b); // Returns a - b __declspec(dllexport) double Subtract(double a, double b); // Returns a * b __declspec(dllexport) double Multiply(double a, double b); // Returns a / b // Throws DivideByZeroException if b is 0 __declspec(dllexport) double Divide(double a, double b); } endif //.cpp include "test.h" include using namespace std; extern double __cdecl Add(double a, double b) { return a + b; } extern double __cdecl Subtract(double a, double b) { return a - b; } extern double __cdecl Multiply(double a, double b) { return a * b; } extern double __cdecl Divide(double a, double b) { if (b == 0) { throw new invalid_argument("b cannot be zero!"); } return a / b; } //C# Program using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; namespace ConsoleApplication1 { class Program { [DllImport("SDES.dll")] public static extern void SimulateGameDLL(int a, int b); static void Main(string[] args) { SimulateGameDLL(1, 2); //Error here... } } } Anyone have any idea's what I may be missing in my program? Let me know if I missed some code or if you have any questions.

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  • [Netbeans 6.9] Java MethodOverloading error with double values

    - by Nimitips
    Here is a part of my code I'm having trouble with: ===Class Overload=== public class Overload { public void testOverLoadeds() { System.out.printf("Square of integer 7 is %d\n",square(7)); System.out.printf("Square of double 7.5 is %d\n",square(7.5)); }//..end testOverloadeds public int square(int intValue) { System.out. printf("\nCalled square with int argument: %d\n",intValue); return intValue * intValue; }//..end square int public double square(double doubleValue) { System.out.printf("\nCalled square with double argument: %d\n", doubleValue); return doubleValue * doubleValue; }//..end square double }//..end class overload ===Main=== public static void main(String[] args) { Overload methodOverload = new Overload(); methodOverload.testOverLoadeds(); } It compiles with no error, however when I try to run it the output is: Called square with int argument: 7 Square of integer 7 is 49 Exception in thread "main" java.util.IllegalFormatConversionException: d != java.lang.Double at java.util.Formatter$FormatSpecifier.failConversion(Formatter.java:3999) at java.util.Formatter$FormatSpecifier.printInteger(Formatter.java:2709) at java.util.Formatter$FormatSpecifier.print(Formatter.java:2661) at java.util.Formatter.format(Formatter.java:2433) at java.io.PrintStream.format(PrintStream.java:920) at java.io.PrintStream.printf(PrintStream.java:821) at methodoverload.Overload.square(Overload.java:19) at methodoverload.Overload.testOverLoadeds(Overload.java:8) at methodoverload.Main.main(Main.java:9) Called square with double argument:Java Result: 1 What am I doing wrong? I'm on Ubuntu 10.10, Netbeans 6.9. Thanks.

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  • My C# UploadFile method successfully uploads a file, but then my UI hangs...

    - by kyrathaba
    I have a simple WinForms test application in C#. Using the following method, I'm able to upload a file when I invoke the method from my button's Click event handler. The only problem is: my Windows Form "freezes". I can't close it using the Close button. I have to end execution from within the IDE (Visual C# 2010 Express edition). Here are the two methods: public void UploadFile(string FullPathFilename) { string filename = Path.GetFileName(FullPathFilename); try { FtpWebRequest request = (FtpWebRequest)WebRequest.Create(_remoteHost + filename); request.Method = WebRequestMethods.Ftp.UploadFile; request.Credentials = new NetworkCredential(_remoteUser, _remotePass); StreamReader sourceStream = new StreamReader(FullPathFilename); byte[] fileContents = Encoding.UTF8.GetBytes(sourceStream.ReadToEnd()); request.ContentLength = fileContents.Length; Stream requestStream = request.GetRequestStream(); requestStream.Write(fileContents, 0, fileContents.Length); FtpWebResponse response = (FtpWebResponse)request.GetResponse(); response.Close(); requestStream.Close(); sourceStream.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message, "Upload error"); } finally { } } which gets called here: private void btnUploadTxtFile_Click(object sender, EventArgs e) { string username = "my_username"; string password = "my_password"; string host = "ftp://mywebsite.com"; try { clsFTPclient client = new clsFTPclient(host + "/httpdocs/non_church/", username, password); client.UploadFile(Path.GetDirectoryName(Application.ExecutablePath) + "\\myTextFile.txt"); } catch (Exception ex) { MessageBox.Show(ex.Message, "Upload problem"); } }

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  • Is it OK to write code after [super dealloc]? (Objective-C)

    - by Richard J. Ross III
    I have a situation in my code, where I cannot clean up my classes objects without first calling [super dealloc]. It is something like this: // Baseclass.m @implmentation Baseclass ... -(void) dealloc { [self _removeAllData]; [aVariableThatBelongsToMe release]; [anotherVariableThatBelongsToMe release]; [super dealloc]; } ... @end This works great. My problem is, when I went to subclass this huge and nasty class (over 2000 lines of gross code), I ran into a problem: when I released my objects before calling [super dealloc] I had zombies running through the code that were activated when I called the [self _removeAllData] method. // Subclass.m @implementation Subclass ... -(void) deallloc { [super dealloc]; [someObjectUsedInTheRemoveAllDataMethod release]; } ... @end This works great, and It didn't require me to refactor any code. My question Is this: Is it safe for me to do this, or should I refactor my code? Or maybe autorelease the objects? I am programming for iPhone if that matters any.

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  • java gui image problem : doesn't display in the background

    - by thegamer
    Hello, i have a query about why is my image not being displayed in my background of my program. I mean i did all the steps necessary and still it would'nt be displayed. The code runs perfectly but without having the image displayed. The directory is written in the good location of the image. I am using java with gui. If anyone could help me solve my problem, i would appreciate :) here is the code below: import java.awt.*; import java.awt.event.*; import javax.swing.*; public class hehe extends JPanel{ public hehe(){ setOpaque(false); setLayout(new FlowLayout()); } public static void main (String args[]){ JFrame win = new JFrame("yooooo"); // it is automaticcally hidden JPanel mainPanel = new JPanel(new BorderLayout()); win.add(mainPanel); JLabel titleLabel = new JLabel("title boss"); titleLabel.setFont(new Font("Arial",Font.BOLD,18)); titleLabel.setForeground(Color.blue); mainPanel.add(titleLabel,BorderLayout.NORTH); win.setSize(382,269); // the dimensions of the image win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); win.setVisible(true); } public void paint(Graphics g) { Image a = Toolkit.getDefaultToolkit().getImage("C:\\Users\\andrea\\Desktop\\Gui\\car"); // car is the name of the image file and is in JPEG g.drawImage(a,0,0,getSize().width,getSize().height,this); super.paint(g); } }

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  • objective-c having issues with an NSDictioary object

    - by Mark
    I have a simple iPhone app that Im learning and I want to have an instance variable called urlLists which is an NSDictionary I have declared it like so: @interface MyViewController : UIViewController <UIPickerViewDataSource, UIPickerViewDelegate>{ IBOutlet UIPickerView *pickerView; NSMutableArray *categories; NSDictionary *urlLists; } @property(retain) NSDictionary *urlLists; @end and in the implementation: @implementation MyViewController @synthesize urlLists; ... - (void)viewDidLoad { [super viewDidLoad]; categories = [[NSMutableArray alloc] init]; [categories addObject:@"Sport"]; [categories addObject:@"Entertainment"]; [categories addObject:@"Technology"]; [categories addObject:@"Political"]; NSArray *objects = [NSArray arrayWithObjects:@"value1", @"value2", @"value3", @"value4", nil]; urlLists = [NSDictionary dictionaryWithObjects:objects forKeys:categories]; for (id key in urlLists) { NSLog(@"key: %@, value: %@", key, [urlLists objectForKey:key]); } } ... @end And, this all works up to here. I have added a UIPicker to my app, and when I select one of the items, I want to Log the one picked and its related entry in my dictionary. -(void) pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger) component { for (id key in self.urlLists) { NSLog(@"key: %@, value: %@", key, [urlLists objectForKey:key]); } } but I get the old EXC_BAD_ACCESS error... I know Im missing something small, but what? Thanks

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  • Which is the best Linux C/C++ debugger (or front-end to gdb) to help teaching programming?

    - by omer.gimenez
    I teach a sort of "lite" C++ programming course to novices ("lite" meaning no pointers, no classes, just plain old C, plus references and STL string and vectors). Students have no previous experience in programming, so I believe that using an interactive debugger would help them understand program flow, variables, and recursion. The course is taught in Linux. Teaching them to use gdb is just overkill (they will not use nor understand most features). I just need something simple but easy to use: to see at which line the program is now, what is in the stack (local variables, previous calls, etc.). I look something similar to old Turbo Pascal or Turbo C++ Borland's debugger, or Visual Studio debugger. Thank you,

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  • C: Fifo between threads, writing and reading strings

    - by Yonatan
    Hello once more dear internet, I writing a small program that among other things, writes a log file of commands received. to do that, I want to use a thread that all it should do is just attempt to read from a pipe, while the main thread will write into that pipe whenever it should. Since i don't know the length of each string command, i thought about writing and reading the pointer to the char buf[MAX_MESSAGE_LEN]. Since what i've tried so far doesn't work, i'll post my best effort :P char str[] = "hello log thread 123456789 10 11 12 13 14 15 16 17 18 19\n"; if (pipe(pipe_fd) != 0) return -1; pthread_t log_thread; pthread_create(&log_thread,NULL, log_thread_start, argv[2]); success_write = 0; do { write(pipe_fd[1],(void*)&str,sizeof(char*)); } while (success_write < sizeof(char*)); and the thread does this: char buffer[MAX_MSGLEN]; int success_read; success_read = 0; //while(1) { do { success_read += read(pipe_fd[0],(void*)&buffer, sizeof(char*)); } while (success_read < sizeof(char*)); //} printf("%s",buffer); (Sorry if this doesn't indent, i can't seem to figure out this editor...) oh, and pipe_fd[2] is a global parameter. So, any help with this, either by the way i thought of, or another way i could read strings without knowing the length, would be much appreciated. On a side note, i'm working on Eclipse IDE C/C++, version 1.2.1 and i can't seem to set up the compiler so it will link the pthread library to my project. I've resorted to writing my own Makefile to make it (pun intended :P) work. Anyone knows what to do ? i've looked online, but all i find are solutions that are probably good on an older version because the tabs and option keys are different. Anyways, Thanks a bunch internet ! Yonatan

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  • implementing a read/write field for an interface that only defines read

    - by PaulH
    I have a C# 2.0 application where a base interface allows read-only access to a value in a concrete class. But, within the concrete class, I'd like to have read/write access to that value. So, I have an implementation like this: public abstract class Base { public abstract DateTime StartTime { get; } } public class Foo : Base { DateTime start_time_; public override DateTime StartTime { get { return start_time_; } internal set { start_time_ = value; } } } But, this gives me the error: Foo.cs(200,22): error CS0546: 'Foo.StartTime.set': cannot override because 'Base.StartTime' does not have an overridable set accessor I don't want the base class to have write access. But, I do want the concrete class to provide read/write access. Is there a way to make this work? Thanks, PaulH Unfortunately, Base can't be changed to an interface as it contains non-abstract functionality also. Something I should have thought to put in the original problem description. public abstract class Base { public abstract DateTime StartTime { get; } public void Buzz() { // do something interesting... } } My solution is to do this: public class Foo : Base { DateTime start_time_; public override DateTime StartTime { get { return start_time_; } } internal void SetStartTime { start_time_ = value; } } It's not as nice as I'd like, but it works.

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  • Silverlight 4 webclient authentication - anyone have this working yet?

    - by Toran Billups
    So one of the best parts about the new Silverlight 4 beta is that they finally implemented the big missing feature of the networking stack - Network Credentials! In the below I have a working request setup, but for some reason I get a "security error" when the request comes back - is this because twitter.com rejected my api call or something that I'm missing in code? It might be good to point out that when I watch this code execute via fiddler it shows that the xml file for cross domain is pulled down successfully, but that is the last request shown by fiddler ... public void RequestTimelineFromTwitterAPI() { WebRequest.RegisterPrefix("https://", System.Net.Browser.WebRequestCreator.ClientHttp); WebClient myService = new WebClient(); myService.AllowReadStreamBuffering = true; myService.UseDefaultCredentials = false; myService.Credentials = new NetworkCredential("username", "password"); myService.UseDefaultCredentials = false; myService.OpenReadCompleted += new OpenReadCompletedEventHandler(TimelineRequestCompleted); myService.OpenReadAsync(new Uri("https://twitter.com/statuses/friends_timeline.xml")); } public void TimelineRequestCompleted(object sender, System.Net.OpenReadCompletedEventArgs e) { //anytime I query for e.Result I get a security error }

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  • Tomcat application: Frequent OutOfMemory PermGen exception while image uploads

    - by rabbit
    Hi, I have a tomcat 6 application which I have set parameters of -Xms512m -Xmx1024m. I thought 1 GB of memory in a 4 GB RAM would be enough, but that is not the case. On application stop/start multiple times (from tomcat manager) and also on image uploads (sometimes) I run into the OutOfMemory PermGen space error and the site stops responding. Should I increase the memory still some more? Is there anything else that I can do to from the tomcat side so that it does not run into the PermGen space issue? Thanks in advance for pointers/tips etc.

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  • Suggested C++ books?

    - by Josh Bradley
    Ok, I've had one semester of C++ and will be taking a second semester in it after I have taken a Data Structure class this fall. In the first class, we dealt mainly with C++ syntax and the textbook we used was ok, but now I'm wanting to go ahead and purchase a great C++ book that encompasses a lot of the programming concepts used today. I'm learning Objective-C on my own and was able to get through the whole object-oriented stuff pretty easily, along with other things like pointers, inheritance, delegation, etc. It doesn't have to exactly have EVERYTHING in it, but I do want to buy the book with the most information in it. Money is no problem. So my question is what book did you use or still use for C++? Is it a book that you can reference back to if you ever forget how to do something small, or would you have to go online and find the answer.

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  • Why doesn't my UIViewController class keep track of an NSArray instance variable.

    - by TaoStoner
    Hey, I am new to Objective-C 2.0 and Xcode, so forgive me if I am missing something elementary here. Anyways, I am trying to make my own UIViewController class called GameView to display a new view. To work the game I need to keep track of an NSArray that I want to load from a plist file. I have made a method 'loadGame' which I want to load the correct NSArray into an instance variable. However it appears that after the method executes the instance variable loses track of the array. Its easier if I just show you the code.... @interface GameView : UIViewController { IBOutlet UIView *view IBOutlet UILabel *label; NSArray *currentGame; } -(IBOutlet)next; -(void)loadDefault; ... @implementation GameView - (IBOutlet)next{ int numElements = [currentGame count]; int r = rand() % numElements; NSString *myString = [currentGame objectAtIndex:(NSUInteger)r]; [label setText: myString]; } - (void)loadDefault { NSDictionary *games; NSString *path = [[NSBundle mainBundle] bundlePath]; NSString *finalPath = [path stringByAppendingPathComponent:@"Games.plist"]; games = [NSDictionary dictionaryWithContentsOfFile:finalPath]; currentGame = [games objectForKey:@"Default"]; } when loadDefault gets called, everything runs perfectly, but when I try to use the currentGame NSArray later in the method call to next, currentGame appears to be nil. I am also aware of the memory management issues with this code. Any help would be appreciated with this problem.

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  • ActionScript shiftKey Not Working In Full Screen Mode?

    - by Chunk1978
    i've drawn an ellipse sprite and added it to the display list of a container, which is added to the display list of the stage. to move the sprites with the keyboard arrows, it appears that my shiftModifier:Number variable is not working when the stage's display state is set to full screen. shiftModifier works as it should when the stage's display state is set to Normal. stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyboardDown); function onKeyboardDown(evt:KeyboardEvent):void { var shiftModifier:Number = 0.25; if (evt.shiftKey) {shiftModifier = 10;} if (evt.keyCode == Keyboard.UP) {ellipse1.y -= shiftModifier;} if (evt.keyCode == Keyboard.DOWN) {ellipse1.y += shiftModifier;} if (evt.keyCode == Keyboard.LEFT) {ellipse1.x -= shiftModifier;} if (evt.keyCode == Keyboard.RIGHT) {ellipse1.x += shiftModifier;} } fsm.addEventListener(MouseEvent.CLICK, toggleFullScreenMode); function toggleFullScreenMode(evt:MouseEvent):void { if (stage.displayState == StageDisplayState.FULL_SCREEN) {stage.displayState = StageDisplayState.NORMAL;} else {stage.displayState = StageDisplayState.FULL_SCREEN;} } full screen is tested in Safari and Firefox.

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  • waiting for a signal

    - by Umesha MS
    Hi, I am working on an application which uploads the content of the file to server. To upload the file to server I am using ‘QNetworkAccessManager’ class. Since it works as asynchronous way, I changed it to work as synchronous way by using QEventLoop. Class FileTransfer { Public : QNetworkAccessManager mNetworkManager; Void Upload(QNetworkRequest request, QIODevice *data) { responce = mNetworkManager.put(request, data); EventLoop.exec(); ReadResponce(responce); } Void Stop() { responce ->close(); } } In my sample application I have 2 windows. 1st to select the files and 2nd to show the progress. When user click on upload button in the first window, the 2nd window will be displayed and then I create the FileTransfer object and start uploading. While uploading the file if user closes the form then in the destructor of the window I call the stop of ‘FileTransfer’ after that I delete the ‘FileTransfer’ object. But here the Upload() function is not yet completed so it will crash. Please help me to: How to wait in 'stop()' function until the Upload() function is completed

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  • How to write syntax highlighting? c++

    - by ML
    Hi All, I am embarking on some learning and I want to write my own syntax highlighting for files in C++. Can anyone give me ideas on how to go about doing this? To me it seems that when a file is opened: 1. it would need to be parsed and decided what type of source file it is. Trusting the extension might not be full-proof a way to know what keywords/commands apply to what language a way to decide what color each keyword/command gets I want to do this on OS X, C++ or Objective-C Can anyone provide pointers on how I might get started with this?

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  • "Exception in thread "main" java.lang.NoSuchMethodError Do i miss library in the installed JDk?

    - by Ahmad
    Hello every body I was using the JDK very well writing the code then i use "javac" to compile it then "java" to run it But Recently when i write a code and compile it then if i try to run it this exception appears to me "Exception in thread "main" java.lang.NoSuchMethodError " at first i thought there is something wrong in my code , i searched in the internet for a solving for this problem but i didn't find anything may help me Then i try to run the "HelloWorld" example i made it before, it runs i copied the code and pasted it in another file and changed the name to "HelloWorld2" and compile it by "javac" and tried to run it by "java" the same exception appears i was surprised why? it is the same code then i used the "javap" which decompile the code with both i found this difference in the first one (the old one) "public static void main(java.lang.String[])"; but in the second (the new one) "public static void main(String[])"; without java.lang then i compiled the old one which works and runs by "javac" and when i try to run it, it didn't run and give me the same exception i tried with some of my old codes it run and when i compile it by "javac" it doesn't work I searched to find a solution to this problem and i found nothing

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  • Linq to NHibernate - How to return a parent object with only certain child objects included

    - by vakman
    Given a simplified model like the following: public class Enquiry { public virtual DateTime Created { get; set; } public virtual Sender Sender { get; set; } } public class Sender { public virtual IList<Enquiry> Enquiries { get; set; } } How can you construct a Linq to Nhibernate query such that it gives you back a list of senders and their enquiries where the enquiries meet some criteria. I have tried something like this: return session.Linq<Enquiry>() .Where(enquiry => enquiry.Created < DateTime.Now) .Select(enquiry => enquiry.Sender) In this case I get an InvalidCastException saying you can't cast type Sender to type Enquiry. Any pointers on how I can do this without using HQL?

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  • std::string constructor corrupts pointer

    - by computergeek6
    I have an Entity class, which contains 3 pointers: m_rigidBody, m_entity, and m_parent. Somewhere in Entity::setModel(std::string model), it's crashing. Apparently, this is caused by bad data in m_entity. The weird thing is that I nulled it in the constructor and haven't touched it since then. I debugged it and put a watchpoint on it, and it comes up that the m_entity member is being changed in the constructor for std::string that's being called while converting a const char* into an std::string for the setModel call. I'm running on a Mac, if that helps (I think I remember some problem with std::string on the Mac). Any ideas about what's going on?

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  • Updating database row from model

    - by Jamie Dixon
    Hey everyone, I'm haing a few problems updating a row in my database using Linq2Sql. Inside of my model I have two methods for updating and saving from my controller, which in turn receives an updated model from my view. My model methods like like: public void Update(Activity activity) { _db.Activities.InsertOnSubmit(activity); } public void Save() { _db.SubmitChanges(); } and the code in my Controller likes like: [HttpPost] public ActionResult Edit(Activity activity) { if (ModelState.IsValid) { UpdateModel<Activity>(activity); _activitiesModel.Update(activity); _activitiesModel.Save(); } return View(activity); } The problem I'm having is that this code inserts a new entry into the database, even though the model item i'm inserting-on-submit contains a primary key field. I've also tried re-attaching the model object back to the data source but this throws an error because the item already exists. Any pointers in the right direction will be greatly appreciated. UPDATE: I'm using dependancy injection to instantiate my datacontext object as follows: IMyDataContext _db; public ActivitiesModel(IMyDataContext db) { _db = db; }

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  • malloc hangs in Linux

    - by Rahul
    I am using Linux on a 16 G with 2 quad core CPU. There are 8 processes which are doing some work (CPU intensive/network i/o). Out of which 4 have a memory leak (These are test conditions so no problem in having leaks here). Total space is occupied by all processes is around 15.4 G only 200 MB is free in system. Things are fine for some hours. But after that malloc hangs (for a process which doesn't have a memory leak). Its stuck for for more than 4 minutes (Note CPU is not 100% but io has gone up signficantly). Now there is no problem in the hanged process. (It has not corrupted the memory). What malloc is doing? (is it tryibg to defragment or builidng up swap space).I am using SUSE 10. Any pointers?

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  • Can't add/remove items from a collection while foreach is iterating over it

    - by flockofcode
    If I make my own implementation of IEnumerator interface, then I am able ( inside foreach statement )to add or remove items from a albumsList without generating an exception.But if foreach statement uses IEnumerator supplied by albumsList, then trying to add/delete ( inside the foreach )items from albumsList will result in exception: class Program { static void Main(string[] args) { string[] rockAlbums = { "rock", "roll", "rain dogs" }; ArrayList albumsList = new ArrayList(rockAlbums); AlbumsCollection ac = new AlbumsCollection(albumsList); foreach (string item in ac) { Console.WriteLine(item); albumsList.Remove(item); //works } foreach (string item in albumsList) { albumsList.Remove(item); //exception } } class MyEnumerator : IEnumerator { ArrayList table; int _current = -1; public Object Current { get { return table[_current]; } } public bool MoveNext() { if (_current + 1 < table.Count) { _current++; return true; } else return false; } public void Reset() { _current = -1; } public MyEnumerator(ArrayList albums) { this.table = albums; } } class AlbumsCollection : IEnumerable { public ArrayList albums; public IEnumerator GetEnumerator() { return new MyEnumerator(this.albums); } public AlbumsCollection(ArrayList albums) { this.albums = albums; } } } a) I assume code that throws exception ( when using IEnumerator implementation A supplied by albumsList ) is located inside A? b) If I want to be able to add/remove items from a collection ( while foreach is iterating over it), will I always need to provide my own implementation of IEnumerator interface, or can albumsList be set to allow adding/removing items? thank you

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  • Purpose of boost::checked_delete

    - by Channel72
    I don't understand the purpose of boost::checked_delete. The documentation says: The C++ Standard allows, in 5.3.5/5, pointers to incomplete class types to be deleted with a delete-expression. When the class has a non-trivial destructor, or a class-specific operator delete, the behavior is undefined. Some compilers issue a warning when an incomplete type is deleted, but unfortunately, not all do, and programmers sometimes ignore or disable warnings. The supplied function and class templates can be used to prevent these problems, as they require a complete type, and cause a compilation error otherwise. So the C++ standard allows you to delete incomplete types, which causes undefined behavior if the type has a non-trivial destructor. What? How can an incomplete type have any destructor at all? Isn't an incomplete type just a prototype?

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