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• Looking for a fast, compact, streamable, multi-language, strongly typed serialization format

  - by sanity

  I'm currently using JSON (compressed via gzip) in my Java project, in which I need to store a large number of objects (hundreds of millions) on disk. I have one JSON object per line, and disallow linebreaks within the JSON object. This way I can stream the data off disk line-by-line without having to read the entire file at once. It turns out that parsing the JSON code (using http://www.json.org/java/) is a bigger overhead than either pulling the raw data off disk, or decompressing it (which I do on the fly). Ideally what I'd like is a strongly-typed serialization format, where I can specify "this object field is a list of strings" (for example), and because the system knows what to expect, it can deserialize it quickly. I can also specify the format just by giving someone else its "type". It would also need to be cross-platform. I use Java, but work with people using PHP, Python, and other languages. So, to recap, it should be: Strongly typed Streamable (ie. read a file bit by bit without having to load it all into RAM at once) Cross platform (including Java and PHP) Fast Free (as in speech) Any pointers?

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• Constructor and Destructors in C++ [Not a question] [closed]

  - by Jack

  I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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• Java downcasting dilemma

  - by Shades88

  please have a look at this code here. class Vehicle { public void printSound() { System.out.print("vehicle"); } } class Car extends Vehicle { public void printSound() { System.out.print("car"); } } class Bike extends Vehicle{ public void printSound() { System.out.print("bike"); } } public class Test { public static void main(String[] args) { Vehicle v = new Car(); Bike b = (Bike)v; v.printSound(); b.printSound(); Object myObj = new String[]{"one", "two", "three"}; for (String s : (String[])myObj) System.out.print(s + "."); } } Executing this code will give ClassCastException saying inheritance.Car cannot be cast to inheritance.Bike. Now look at the line Object myObj = new String[]{"one", "two", "three"};. This line is same as Vehicle v = new Car(); right? In both lines we are assigning sub class object to super class reference variable. But downcasting String[]myObj is allowed but (Bike)v is not. Please help me understand what is going on around here.

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• Implementing list position locator in C++?

  - by jfrazier

  I am writing a basic Graph API in C++ (I know libraries already exist, but I am doing it for the practice/experience). The structure is basically that of an adjacency list representation. So there are Vertex objects and Edge objects, and the Graph class contains: list<Vertex *> vertexList list<Edge *> edgeList Each Edge object has two Vertex* members representing its endpoints, and each Vertex object has a list of Edge* members representing the edges incident to the Vertex. All this is quite standard, but here is my problem. I want to be able to implement deletion of Edges and Vertices in constant time, so for example each Vertex object should have a Locator member that points to the position of its Vertex* in the vertexList. The way I first implemented this was by saving a list::iterator, as follows: vertexList.push_back(v); v->locator = --vertexList.end(); Then if I need to delete this vertex later, then rather than searching the whole vertexList for its pointer, I can call: vertexList.erase(v->locator); This works fine at first, but it seems that if enough changes (deletions) are made to the list, the iterators will become out-of-date and I get all sorts of iterator errors at runtime. This seems strange for a linked list, because it doesn't seem like you should ever need to re-allocate the remaining members of the list after deletions, but maybe the STL does this to optimize by keeping memory somewhat contiguous? In any case, I would appreciate it if anyone has any insight as to why this happens. Is there a standard way in C++ to implement a locator that will keep track of an element's position in a list without becoming obsolete? Much thanks, Jeff

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• How to get a Class literal from a generically specific Class

  - by h2g2java

  There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

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• getting a "default" concrete class that implements an interface

  - by Roger Joys

  I am implementing a custom (and generic) Json.net serializer and hit a bump in the road that I could use some help on. When the deserializer is mapping to a property that is an interface, how can I best determine what sort of object to construct to deserialize to to place into the interface property. I have the following: [JsonConverter(typeof(MyCustomSerializer<foo>))] class foo { int Int1 { get; set; } IList<string> StringList {get; set; } } My serializer properly serializes this object, and but when it comes back in, and I try to map the json parts to to object, I have a JArray and an interface. I am currently instantiating anything enumerable like List as theList = Activator.CreateInstance(property.PropertyType); This works create to work with in the deserialization process, but when the property is IList, I get runtime complaints (obviously) about not being able to instantiate an interface. So how would I know what type of concrete class to create in a case like this? Thank you

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• Serialize Forms into memory

  - by serhio

  Background: In a desktop MDI application we have a lot of forms. Task: Save the controls contents of closed forms(textbox texts, checkbox checks etc). Limitations: A saved form for (DB/Windows) user? For (DB/Windows) group of users? Both variants may be possible. Question: a) What is the best way? b) if I want do not use files, how to serialize the form into a MemoryStream and then recuperate it if the opening form was been once opened and serialized? StartingPoint: Implemented a form that implements ISerializable. Deserialize the form on opening, serialize onclosing: Public Sub GetObjectData(ByVal info As System.Runtime.Serialization.SerializationInfo, ByVal context As System.Runtime.Serialization.StreamingContext) Implements System.Runtime.Serialization.ISerializable.GetObjectData info.AddValue("tbxExportFolder", tbxExportFolder.Text, GetType(String)) info.AddValue("cbxCheckAliasUnicity", cbxCheckAliasUnicity.Checked, GetType(Boolean)) End Sub Public Sub New(ByVal info As SerializationInfo, ByVal context As StreamingContext) Me.New() Me.tbxExportFolder.Text = info.GetString("tbxExportFolder") Me.cbxCheckAliasUnicity.Checked = info.GetBoolean("cbxCheckAliasUnicity") End Sub Private Sub SerializeMe() Dim binFormatter As New Formatters.Binary.BinaryFormatter Dim fileStream As New FileStream(SerializedFilename, FileMode.Create) Try binFormatter.Serialize(fileStream, Me) Catch Throw Finally fileStream.Close() End Try End Sub Protected Overrides Sub OnClosing(ByVal e As System.ComponentModel.CancelEventArgs) SerializeMe() MyBase.OnClosing(e) End Sub

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• Thread-safe data structure design

  - by Inso Reiges

  Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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• View transform seems to be ignored when animating on iphone. Why?

  - by heymon

  I have views that can be rotated, scaled and moved around the screen. I want the view to resize and be orthogonal when the user double tap's the view to edit the textview within. The code is below. Somewhere the transform is getting reset. The NSLog statement below prints the identity transform, but a print of the transform when the animation is complete in transitionDidStop reveals that the transform is what it was before I thought I set it to identity. The view resizes, but it acts like the transform was never set to identity? Any ideas/pointers? originalBounds = self.bounds; originalCenter = self.center; originalTransform = self.transform; r = CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width - 70, 450); [UIView beginAnimations: nil context: NULL]; [UIView setAnimationDelegate: self]; [UIView setAnimationDidStopSelector: @selector(transitionDidStop:finished:context:)]; self.transform = CGAffineTransformIdentity; NSLog(@"%@ after set", NSStringFromCGAffineTransform([self transform])); [self setBounds: r]; [self setCenter: p]; [self setAlpha: 1.0]; [UIView commitAnimations]; [textView becomeFirstResponder];

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• HttpPostedFile.SaveAs() throws UnauthorizedAccessException even though the file is saved?

  - by jrummell

  I have an aspx page with multiple FileUpload controls and one Upload button. In the click handler I save the files like this: string path = "..."; for (int i = 0; i < Request.Files.Count - 1; i++) { HttpPostedFile file = Request.Files[i]; string fileName = Path.GetFileName(file.FileName); string saveAsPath = Path.Combine(path, fileName); file.SaveAs(saveAsPath); } When file.SaveAs() is called, it throws: System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. --- System.UnauthorizedAccessException: Access to the path '...' is denied. at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy) at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy) at System.IO.FileStream..ctor(String path, FileMode mode) at System.Web.HttpPostedFile.SaveAs(String filename) at Belden.Web.Intranet.Iso.Complaints.AttachmentUploader.btnUpload_Click(Object sender, EventArgs e) at System.Web.UI.WebControls.Button.OnClick(EventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace --- at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequest(HttpContext context) at ASP.departments_iso_complaints_uploadfiles_aspx.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Now here's the fun part. The file is saved correctly! So why is it throwing this exception?

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• Android ArrayList<Location> passing between activities

  - by squixy

  I have simple class Track, which stores information about route: import java.io.Serializable; import java.util.ArrayList; import java.util.Date; import android.location.Location; public class Track implements Serializable { private static final long serialVersionUID = -5317697499269650204L; private Date date; private String name; private int time; private double distance, speed; private ArrayList<Location> route; public Track(String name, int time, double distance, ArrayList<Location> route) { this.date = new Date(); this.name = name; this.time = time; this.distance = distance; this.speed = distance / (time / 3600.); this.route = route; } public String getDate() { return String.format("Date: %1$td-%1$tb-%1$tY%nTime: %1$tH:%1$tM:%1$tS", date); } public String getName() { return name; } public int getTime() { return time; } public double getDistance() { return distance; } public float getSpeed() { return (float) speed; } public ArrayList<Location> getRoute() { return route; } @Override public String toString() { return String.format("Name: %s%nDate: %2$td-%2$tb-%2$tY%nTime: %2$tH:%2$tM:%2$tS", name, date); } } And I'm passing it from one activity to another: Intent showTrackIntent = new Intent(TabSavedActivity.this, ShowTrackActivity.class); showTrackIntent.putExtra("track", adapter.getItem(position)); startActivity(showTrackIntent); Where (Track object is element on ListView). I get error during passing Track object: java.lang.RuntimeException: Parcelable encountered IOException writing serializable object (name = classes.Track) What is happening?

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• Adding defaults and indexes to a script/generate command in a Rails Template?

  - by charliepark

  I'm trying to set up a Rails Template that would allow for comprehensive set-up of a specific Rails app. Using Pratik Naik's overview (http://m.onkey.org/2008/12/4/rails-templates), I was able to set up a couple of scaffolds and models, with a line that looks something like this ... generate("scaffold", "post", "title:string", "body:string") I'm now trying to add in Delayed Jobs, which normally has a migration file that looks like this: create_table :delayed_jobs, :force => true do |table| table.integer :priority, :default => 0 # Allows some jobs to jump to the front of the queue table.integer :attempts, :default => 0 # Provides for retries, but still fail eventually. table.text :handler # YAML-encoded string of the object that will do work table.text :last_error # reason for last failure (See Note below) table.datetime :run_at # When to run. Could be Time.now for immediately, or sometime in the future. table.datetime :locked_at # Set when a client is working on this object table.datetime :failed_at # Set when all retries have failed (actually, by default, the record is deleted instead) table.string :locked_by # Who is working on this object (if locked) table.timestamps end So, what I'm trying to do with the Rails template, is to add in that :default = 0 into the master template file. I know that the rest of the template's command should look like this: generate("migration", "createDelayedJobs", "priority:integer", "attempts:integer", "handler:text", "last_error:text", "run_at:datetime", "locked_at:datetime", "failed_at:datetime", "locked_by:string") Where would I put (or, rather, what is the syntax to add) the :default values in that? And if I wanted to add an index, what's the best way to do that?

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• placing pop up based on the mouse position(x,y)RSS Feed

  - by prince23

  hi, right now i am showing pop at the botton of the screen. i need to change them according to the value(x,y) whhere i have moved the mouse here i need to get the MouseEventArgs e postion that is its x:value and y:value based on that i need to place the pop up in the screen i need to get the mouse x, y postion? is it possiable to get its value? private void DG_LoadingRow(object sender, DataGridRowEventArgs e) { DataGridRow row = e.Row; int index = 0; foreach (DataGridColumn colGrid in DG.Columns) { if(colGrid .Header == "ID" || colGrid .Header == "Name") { FrameworkElement cellContent = colGrid .GetCellContent(e.Row); DataGridCell cell = cellContent.Parent as DataGridCell; cell.MouseEnter -= cell_MouseEnter; cell.MouseEnter += new MouseEventHandler(cell_MouseEnter); cell.MouseLeave -= cell_MouseLeave; cell.MouseLeave += new MouseEventHandler(cell_MouseLeave); } } } void cell_MouseLeave(object sender, MouseEventArgs e) { //Hide your popup } void cell_MouseEnter(object sender, MouseEventArgs e) { **// here i need to get the mouse position that is its x,y value based on that i can place my modal pop up in that postion. my pop is defined in xaml page here i will be assigning only its position where i need to place my modal pop up.** //

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• Read specific line from text file, according to Checked Listbox selection number.

  - by Manolis

  Heya, i want to create an application which will read a specific line from a text file and show it in a textbox. The line will be chosen according to the number of the listbox selection i will make. Here's the code: Public Class Form1 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim i As Integer For i = 0 To Me.CheckedListBox1.CheckedIndices.Count - 1 Me.CheckedListBox1.SetItemChecked(Me.CheckedListBox1.CheckedIndices(0),False) Next i End Sub Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click If CheckedListBox1.CheckedItems.Count <> 0 Then Dim reader As New System.IO.StreamReader(CurDir() & "\" & "READ.txt") Dim x As Integer Dim s As String = "" For x = 0 To CheckedListBox1.CheckedItems.Count - 1 s = s & "Answer " & (x + 1).ToString & ") " & CheckedListBox1.CheckedItems(x).ToString & ControlChars.CrLf & reader.ReadLine() & ControlChars.CrLf & ControlChars.CrLf Next x Answer.Text = (s) Else MessageBox.Show("Please select questions.", "Error", _ MessageBoxButtons.OK, _ MessageBoxIcon.Information) Return End If End Sub End Class So lets say i 'check' the first, second, and fifth items from the checked listbox, i want it to read from the text file the first, second, and fifth lines of text and show them in the textbox. The current code just reads line 1, 2, 3 (...) in order, no matter what item i have 'checked'. Thanks in advance!

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• Getting around IBActions limited scope

  - by Septih

  Hello, I have an NSCollectionView and the view is an NSBox with a label and an NSButton. I want a double click or a click of the NSButton to tell the controller to perform an action with the represented object of the NSCollectionViewItem. The Item View is has been subclassed, the code is as follows: #import <Cocoa/Cocoa.h> #import "WizardItem.h" @interface WizardItemView : NSBox { id delegate; IBOutlet NSCollectionViewItem * viewItem; WizardItem * wizardItem; } @property(readwrite,retain) WizardItem * wizardItem; @property(readwrite,retain) id delegate; -(IBAction)start:(id)sender; @end #import "WizardItemView.h" @implementation WizardItemView @synthesize wizardItem, delegate; -(void)awakeFromNib { [self bind:@"wizardItem" toObject:viewItem withKeyPath:@"representedObject" options:nil]; } -(void)mouseDown:(NSEvent *)event { [super mouseDown:event]; if([event clickCount] > 1) { [delegate performAction:[wizardItem action]]; } } -(IBAction)start:(id)sender { [delegate performAction:[wizardItem action]]; } @end The problem I've run into is that as an IBAction, the only things in the scope of -start are the things that have been bound in IB, so delegate and viewItem. This means that I cannot get at the represented object to send it to the delegate. Is there a way around this limited scope or a better way or getting hold of the represented object? Thanks.

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• Web service performing asynchronous call

  - by kornelijepetak

  I have a webservice method FetchNumber() that fetches a number from a database and then returns it to the caller. But just before it returns the number to the caller, it needs to send this number to another service so instantiates and runs the BackgroundWorker whose job is to send this number to another service. public class FetchingNumberService : System.Web.Services.WebService { [WebMethod] public int FetchNumber() { int value = Database.GetNumber(); AsyncUpdateNumber async = new AsyncUpdateNumber(value); return value; } } public class AsyncUpdateNumber { public AsyncUpdateNumber(int number) { sendingNumber = number; worker = new BackgroundWorker(); worker.DoWork += asynchronousCall; worker.RunWorkerAsync(); } private void asynchronousCall(object sender, DoWorkEventArgs e) { // Sending a number to a service (which is Synchronous) here } private int sendingNumber; private BackgroundWorker worker; } I don't want to block the web service (FetchNumber()) while sending this number to another service, because it can take a long time and the caller does not care about sending the number to another service. Caller expects this to return as soon as possible. FetchNumber() makes the background worker and runs it, then finishes (while worker is running in the background thread). I don't need any progress report or return value from the background worker. It's more of a fire-and-forget concept. My question is this. Since the web service object is instantiated per method call, what happens when the called method (FetchNumber() in this case) is finished, while the background worker it instatiated and ran is still running? What happens to the background thread? When does GC collect the service object? Does this prevent the background thread from executing correctly to the end? Are there any other side-effects on the background thread? Thanks for any input.

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• Is it possible to replace values ina queryset before sending it to your template?

  - by Issy

  Hi Guys, Wondering if it's possible to change a value returned from a queryset before sending it off to the template. Say for example you have a bunch of records Date | Time | Description 10/05/2010 | 13:30 | Testing... etc... However, based on the day of the week the time may change. However this is static. For example on a monday the time is ALWAYS 15:00. Now you could add another table to configure special cases but to me it seems overkill, as this is a rule. How would you replace that value before sending it to the template? I thought about using the new if tags (if day=1), but this is more of business logic rather then presentation. Tested this in a custom template tag def render(self, context): result = self.model._default_manager.filter(from_date__lte=self.now).filter(to_date__gte=self.now) if self.day == 4: result = result.exclude(type__exact=2).order_by('time') else: result = result.order_by('type') result[0].time = '23:23:23' context[self.varname] = result return '' However it still displays the results from the DB, is this some how related to 'lazy' evaluation of templates? Thanks! Update Responding to comments below: It's not stored wrong in the DB, its stored Correctly However there is a small side case where the value needs to change. So for example I have a From Date & To date, my query checks if todays date is between those. Now with this they could setup a from date - to date for an entire year, and the special cases (like mondays as an example) is taken care off. However if you want to store in the DB you would have to capture several more records to cater for the side case. I.e you would be capturing the same information just to cater for that 1 day when the time changes. (And the time always changes on the same day, and is always the same)

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• Can't draw UImage in UIView::drawRect

  - by Joel

  I know this seems like a simple task, which is why I don't understand why I can't get the image to render. When I set up my UIView, I do the following: myUiView.backgroundColor = [UIColor clearColor]; myUiView.opaque = NO; I create and retain the UIImage in the init function of my UIView: image = [[UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"test" ofType:@"png"]] retain]; then my drawRect looks like this: - (void) drawRect:(CGRect) rect { [image drawInRect:self.bounds]; } Ultimately I'll be manipulating that UIImage via bitmap context, and then in drawRect create a CGImage out of the context, and render that, but for now I'm just trying to get it rendering a known image. I've been digging through this site, as well as the documentation. I've gone down the CG path and tried drawing it with CGContextDrawImage by following the numerous examples other people have posted, but that didn't work either. So I've come back to what seems to be the most straightforward way to draw an image, but it isn't working. Any help would be greatly appreciated. Thanks in advance.

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• Rails Tableless Model

  - by mplacona

  I'm creating a tableless Rails model, and am a bit stuck on how I should use it. Basically I'm trying to create a little application using Feedzirra that scans a RSS feed every X seconds, and then sends me an email with only the updates. I'm actually trying to use it as an activerecord model, and although I can get it to work, it doesn't seem to "hold" data as expected. As an example, I have an initializer method that parses the feed for the first time. On the next requests, I would like to simply call the get_updates method, which according to feedzirra, is the existing object (created during the initialize) that gets updated with only the differences. I'm finding it really hard to understand how this all works, as the object created on the initialize method doesn't seem to persist across all the methods on the model. My code looks something like: def initialize feed parse here end def get_updates feedzirra update passing the feed object here end Not sure if this is the right way of doing it, but it all seems a bit confusing and not very clear. I could be over or under-doing here, but I'd like your opinion about this approach. Thanks in advance

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• How can I intercept an exception occurred during serialization in WCF?

  - by bonomo

  I have a legit data object with all data contract / data member attributes. For some reason the WCF service crashes after the operation has completed and the result is passed as a return value. I believe it has something to do with WCF not being able to serialize that result properly. The test client doesn't say anything specific: The underlying connection was closed: The connection was closed unexpectedly. Server stack trace: at System.ServiceModel.Channels.HttpChannelUtilities.ProcessGetResponseWebException(WebException webException, HttpWebRequest request, HttpAbortReason abortReason) at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout) at System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout) at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation) at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message) Exception rethrown at [0]: at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) at IFacade.PickSecurities(String pattern, Int32 atMost) at FacadeClient.PickSecurities(String pattern, Int32 atMost) Inner Exception: The underlying connection was closed: The connection was closed unexpectedly. at System.Net.HttpWebRequest.GetResponse() at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout) I am in control of creating the instance of the service using a customized service host factory. I know I can set up trace listeners and check the logs, but it's a lot of hassle to do. So I would rather handle it explicitly on the server at the time it happens. So I how can I intercept that exception programmatically and return an appropriate fault meassage?

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• How to re-prompt after a trap return in bash?

  - by verbose

  I have a script that is supposed to trap SIGTERM and SIGTSTP. This is what I have in the main block: trap 'killHandling' TERM And in the function: killHandling () { echo received kill signal, ignoring return } ... and similar for SIGINT. The problem is one of user interface. The script prompts the user for some input, and if the SIGTERM or SIGINT occurs when the script is waiting for input, it's confusing. Here is the output in that case: Enter something: # SIGTERM received received kill signal, ignoring # shell waits at blank line for user input, user gets confused # user hits "return", which then gets read as blank input from the user # bad things happen because of the blank input I have definitely seen scripts which handle this more elegantly, like so: Enter something: # SIGTERM received received kill signal, ignoring Enter something: # re-prompts user for user input, user is not confused What is the mechanism used to accomplish the latter? Unfortunately I can't simply change my trap code to do the re-prompt as the script prompts the user for several things and what the prompt says is context-dependent. And there has to be a better way than writing context-dependent trap functions. I'd be very grateful for any pointers. Thanks!

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• @attribute elements in XML

  - by danit

  Here is my XML: ["link"]=> array(2) { [0]=> object(SimpleXMLElement)#244 (1) { ["@attributes"]=> array(3) { ["type"]=> string(9) "text/html" ["href"]=> string(48) "http://twitter.com/MoodleDan/statuses/1226112723" ["rel"]=> string(9) "alternate" } } [1]=> object(SimpleXMLElement)#245 (1) { ["@attributes"]=> array(3) { ["type"]=> string(9) "image/png" ["href"]=> string(59) "http://a3.twimg.com/profile_images/226895523/Dan_normal.png" ["rel"]=> string(5) "image" } } } ["author"]=> object(SimpleXMLElement)#246 (2) { ["name"]=> string(14) "Dan Humpherson" ["uri"]=> string(16) "http://vl3.co.uk" } The above XML is part of a larger array, but how do i get the href -> ["href"]=> string(59) "http://a3.twimg.com/profile_images/226895523/Dan_normal.png" Element to echo in PHP? This is what I tried (Wrong I know) foreach ($entry->link as $img) { echo $img->href; echo "<img src='". $img ."' />"; }

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• Proper status codes for JSON responses to Ajax calls?

  - by anonymous coward

  My project is returning JSON to Ajax calls from the browser. I'm wondering what the proper status code is for sending back with responses to invalid (but successfully handled) data submissions. For example, jQuery has the following two particular callbacks when making Ajax requests: success: Fired when a 200/2xx status code is delivered along with the response. error: Fired when 4xx, 5xx, etc, status codes come back with the response. If a user attempts to create a new "Person" object, I send back a JSON representation of the newly created object upon success, thus giving javascript access to the necessary unique ID's for the new object, etc. This, of course, is sent with a 200 status code. If a user submits malformed or invalid data (say, an invalid/incomplete "name" field), I would like to send back the validation error messages via JSON. (I don't see why this would be a bad thing). My question is: in doing so, should I send a 200 status code, because I successfully handled their invalid data? Therefore, I'd be using the jQuery success callback, but simply check for errors... Or, should I use a 4xx status code, perhaps 'Bad Request', because the data they sent me is invalid? (and thus, use the error callback to do the necessary client-side notifications).

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• Implementation of delegates in C#

  - by Ram

  Hi, I am trying to learn on how to use delegates efficiently in C# and I was just wondering if anyone can guide me through... The following is a sample implementation using delegates... All I am doing is just passing a value through a delegate from one class to another... Please tell me if this is the right way to implement... And also your suggestions... Also, please note that I have de-registered the delegate in : void FrmSample_FormClosing(object sender, FormClosingEventArgs e) { sampleObj.AssignValue -= new Sample.AssignValueDelegate(AssignValue); } Is this de-registration necessary? The following is the code that I have written.. public partial class FrmSample : Form { Sample sampleObj; public FrmSample() { InitializeComponent(); this.Load += new EventHandler(FrmSample_Load); this.FormClosing += new FormClosingEventHandler(FrmSample_FormClosing); sampleObj = new Sample(); sampleObj.AssignValue = new Sample.AssignValueDelegate(AssignValue); } void FrmSample_FormClosing(object sender, FormClosingEventArgs e) { sampleObj.AssignValue -= new Sample.AssignValueDelegate(AssignValue); } void FrmSample_Load(object sender, EventArgs e) { sampleObj.LoadValue(); } void AssignValue(string value) { MessageBox.Show(value); } } class Sample { public delegate void AssignValueDelegate(string value); public AssignValueDelegate AssignValue; internal void LoadValue() { if (AssignValue != null) { AssignValue("This is a test message"); } } } Pls provide your feedback on whether this is right... Thanks, Ram

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• Convenient way to do "wrong way rebase" in git?

  - by Kaz

  I want to pull in newer commits from master into topic, but not in such a way that topic changes are replayed over top of master, but rather vice versa. I want the new changes from master to be played on top of topic, and the result to be installed as the new topic head. I can get exactly the right object if I rebase master to topic, the only problem being that the object is installed as the new head of master rather than topic. Is there some nice way to do this without manually shuffling around temporary head pointers? Edit: Here is how it can be achieved using a temporary branch head, but it's clumsy: git checkout master git checkout -b temp # temp points to master git rebase topic # topic is brought into temp, temp changes played on top Now we have the object we want, and it's pointed at by temp. git checkout topic git reset --hard temp Now topic has it; and all that is left is to tidy up by deleting temp: git branch -d temp Another way is to to do away with temp and just rebase master, and then reset topic to master. Finally, reset master back to what it was by pulling its old head from the reflog, or a cut-and-paste buffer.

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