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  • How important is managing memory in Objective-C?

    - by Alex Mcp
    Background: I'm (jumping on the bandwagon and) starting learning about iPhone/iPad development and Objective-C. I have a great background in web development and most of my programming is done in javascript (no libraries), Ruby, and PHP. Question: I'm learning about allocating and releasing memory in Objective-C, and I see it as quite a tricky task to layer on top of actually getting the farking thing to run. I'm trying to get a sense of applications that are out there and what will happen with a poorly memory-managed program. A) Are apps usually released with no memory leaks? Is this a feasible goal, or do people more realistically just excise the worst offenders and that's ok? B) If I make an NSString for a title of a view, let's say, and forget to deallocate it it, does this really only become a problem if I recreate that string repeatedly? I imagine what I'm doing is creating an overhead of the memory needed to store that string, so it's probably quite piddling (a few bytes?) However if I have a rapidly looping cycle in a game that 'leaks' an int every cycle or something, that would overflow the app quite quickly. Are these assumptions correct? Sorry if this isn't up the community-wiki alley, I'm just trying to get a handle on how to think about memory and how careful I'll need to be. Any anecdotes or App Store-submitted app experiences would be awesome to hear as well.

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  • Using Git with shared (symbolic link) directories

    - by chmike
    I'm working on a big Qt application with multiple widgets which are quite complex. One of this widget is a webcam stream viewer. The application is organized so that each program module (i.e. widgets) is stored in its own directory with a .pri file. All these are stored in one main directory grouping all the widget directories. Next to this main project directory I also have application directories. Let say one for each widget. In these directory I have a symbolic link (alias on windows) to the module directory in the main project folder. This application has then the necessary code to build a standalone application showing only the widget. So for instance I have a webcam viewer application, another to control some devices, etc. This source code organization works well and allows me to develop and test the widgets in independent applications while sharing the code with the main application. Currently only the main project directory is under version control using subversion. Now I would like to start using git and would like to know if this shared directory model would work with it or if there is a better way to do it.

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  • According to MSDN ReadFile() Win32 function may incorrectly report read operation completion. When?

    - by Martin Dobšík
    The MSDN states in its description of ReadFile() function (http://msdn.microsoft.com/en-us/library/aa365467%28VS.85%29.aspx): “If hFile is opened with FILE_FLAG_OVERLAPPED, the lpOverlapped parameter must point to a valid and unique OVERLAPPED structure, otherwise the function can incorrectly report that the read operation is complete.” I have some applications that are violating the above recommendation and I would like to know the severity of the problem. I mean the program uses named pipe that has been created with FILE_FLAG_OVERLAPPED, but it reads from it using the following call: ReadFile(handle, &buf, n, &n_read, NULL); That means it passes NULL as the lpOverlapped parameter. That call should not work correctly in some circumstances according to documentation. I have spent a lot of time trying to reproduce the problem, but I was unable to! I always got all data in right place at right time. I was testing only Named Pipes though. Would anybody know when can I expect that ReadFile() will incorrectly return and report successful completion even the data are not yet in the buffer? What would have to happen in order to reproduce the problem? Does it happen with files, pipes, sockets, consoles, or other devices? Do I have to use particular version of OS? Or particular version of reading (like register the handle to I/O completion port)? Or particular synchronization of reading and writing processes/threads? Or when would that fail? It works for me :/ Please help! With regards Martin

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  • WCF, ASMX Basic HTTP binding and IIS

    - by Brennan Mann
    Hello, I have been doing a lot of work with WCF "self" hosted applications. I recently was requested to write a web service where the calling client was a Linux based program named "WGET". I would like to use WCF instead of a traditional ASMX web service. The web service is returning a standard XML response. I am not sure of the underlining details between the two technologies but I know WCF is the proper route. I created a WCF service to be hosted in IIS ( using basicHttpBinding). 1.) Did classic ASMX web services ( standard HTTP POST/GET) use SOAP to return responses? I created an class from XSD for the web service response. What is really going on behind the scenes? Is there just special XML HTTP headers that know how to handle to response? Is the response not wrapped in SOAP? The traditional ASMX web service worked perfectly with the class I generated using the .Net "XSD" program. 2.) I want to use WCF for this service. Will using basicHttpBinding work? As I have read, that is the correct binding to use for ASMX clients. Does this use SOAP, standard HTTP headers, or something else? 3.) This is a dumb question because I have not done a lot of web service programming. I noticed on the ASMX default landing page there were examples for responses and code to invoke the functionality. When I create the same service using WCF, I had to create a client application to perform these tasks. Is there a way to expose the WCF endpoint like a classic ASMX service or is the WSDL the only route? As always, I really appreciate the feedback. Thanks, Brennan

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  • Duration of Excessive GC Time in "java.lang.OutOfMemoryError: GC overhead limit exceeded"

    - by jilles de wit
    Occasionally, somewhere between once every 2 days to once every 2 weeks, my application crashes in a seemingly random location in the code with: java.lang.OutOfMemoryError: GC overhead limit exceeded. If I google this error I come to this SO question and that lead me to this piece of sun documentation which expains: The parallel collector will throw an OutOfMemoryError if too much time is being spent in garbage collection: if more than 98% of the total time is spent in garbage collection and less than 2% of the heap is recovered, an OutOfMemoryError will be thrown. This feature is designed to prevent applications from running for an extended period of time while making little or no progress because the heap is too small. If necessary, this feature can be disabled by adding the option -XX:-UseGCOverheadLimit to the command line. Which tells me that my application is apparently spending 98% of the total time in garbage collection to recover only 2% of the heap. But 98% of what time? 98% of the entire two weeks the application has been running? 98% of the last millisecond? I'm trying to determine a best approach to actually solving this issue rather than just using -XX:-UseGCOverheadLimit but I feel a need to better understand the issue I'm solving.

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  • SQL Server 2008 - Editing Tables: Bit columns require 'True' or 'False'

    - by CJM
    Not so much a question as an observation... I'm just upgrading to SQL Server 2008 on my development machine in anticipation of upgrading my live applications. I didn't anticipate any problems since [I think] I generally use standard T-SQL, and probably not too far from ANSI standard SQL. So far so good, but I was really thrown by a very simple change: I was creating a simple, small look-up table to store a list of codes and including a bit column to indicate the current default code. But when I used the new/modified 'Edit Top 200 Rows' option, and entered my 0s and 1s in the the bit column I got an error: 'Invalid value for cell - String was not recognised as a valid boolean' After a bit of head-scratching, I tried True and False - and they worked. So it seems this new Edit feature requires 4 or 5 characters to be typed, rather than the previous 1. Checking further, we can still use '...where bitval = 1' but can now also use '...where bitval = 'true''. But any results returned render these bit columns as 0 or 1 still. It all sounds like half a step backwards. Not the end of the world, but and unnecessary annoyance. Does anybody have any insight on this issue? Or there any other new Gotchas with SQL Server 2008?

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  • NSBundle loading a NSViewController

    - by Staros
    Hey all, I'm looking into a project that would upload custom NSBundles that include a NSViewController. In my main program I've got this code to deal with the bundle after it's been loaded... id principalClass = [loadedBundle principalClass]; id instance = [[principalClass alloc] init]; [localLabel setStringValue:[instance name]]; NSView *incomingView = [[instance viewController] view]; [localView addSubview:incomingView]; [localView display]; And the principal classes init method in the bundle looks like this... -(id) init { if(self = [super init]){ name = @"My Plugin"; viewController = [[ViewController alloc] initWithNibName:@"View" bundle:nil]; } return self; } View.nib is a nib located in the bundles project. But whenever I load the bundle I get this error... 2010-05-27 09:11:18.423 PluginLoader[45032:a0f] unable to find nib named: View in bundle path: (null) 2010-05-27 09:11:18.424 PluginLoader[45032:a0f] -[NSViewController loadView] could not load the "View" nib. I know I've got everything wired up because the line [label setStringValue:[instance name]]; sets the label text correctly. Plus, if I take all of the clases in the bundle and load them into my main applications project everything works as expect. Any thoughts on how I can correctly reference "View" in my bundle? Thanks!

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  • Stopping the service and the babysited application before uninstalling

    - by Viv Coco
    Hi all, I have a service MyService.exe that is babysitting my application MyApp.exe, meaning it starts the application when this one crashes or whatever. Basically when the service is stopped the application is stopped (by the service) and when the service is started the application is started by the service. In order to stop my service and by that my application when uninstalling I'm doing: <ServiceControl Id='MyServiceControl' Name='MyServiceForTest' Start='install' Stop='uninstall' Remove='uninstall'/> But when I want to uninstall everything I get the error message: "The setup must update files or services that cannot be updated while the system is running. If you choose to continue, a reboot will be required to complete the setup.". If I manually stop the service before running the uninstaller I don't get this msg as both my service and my application aren't then running anymore. In the log file I noticed that this happens in InstallValidate and I get this message b/c of MyApp.exe being running. I think what happens is: the uninstallers checks the running applications, it notices that the MyService.exe and MyApp.exe are both running, detects probably that the MyService.exe will be stopped by the uninstaller itself as instructed, but doesn't know about the MyApp.exe that this one will also be terminated once the service will be stopped so it will show the reboot-message. I can't just close MyApp.exe from uninstaller b/c the service will restart it again. How could I solve this problem so that the user won't need to reboot or to manually stop the service before doing an uninstall/upgrade? Also, I can't change MyService and MyApp code anymore so I will have to do this from the (un)installer only. TIA, Viv

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  • Delphi 2009: How do I prevent network application from leaking critical section?

    - by eed3si9n
    As part of Vista certification, Microsoft wants to make sure that an application exits without holding on to a lock (critical section): TEST CASE 31. Verify application does not break into a debugger with the specified AppVerifier checks (Req:3.2) As it turns out, network applications built using Delphi 2009 does break into the debugger, which displays unhelpful message as follows: (1214.1f10): Break instruction exception - code 80000003 (first chance) eax=00000001 ebx=07b64ff8 ecx=a6450000 edx=0007e578 esi=0017f7e0 edi=80000003 eip=77280004 esp=0017f780 ebp=0017f7ac iopl=0 nv up ei pl zr na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000246 *** ERROR: Symbol file could not be found. Defaulted to export symbols for C:\Windows\SysWOW64\ntdll.dll - ntdll!DbgBreakPoint: 77280004 cc int 3 After hitting Go button several times, you come across the actual error: ======================================= VERIFIER STOP 00000212: pid 0x18A4: Freeing virtual memory containing an active critical section. 076CC5DC : Critical section address. 01D0191C : Critical section initialization stack trace. 075D0000 : Memory block address. 00140000 : Memory block size. ======================================= This verifier stop is continuable. After debugging it use `go' to continue. ======================================= Given that my code does not leak TCriticalSection, how do I prevent Delphi from doing so.

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  • Is it possible to use theme colors in Windows Forms apps?

    - by Yadyn
    I normally make use of System Colors whenever possible when designing Windows Forms applications just so that it'll fit in with the user's preferences. But is it possible to use Theme Colors? I realize that this limits you in several ways (must be running Windows that supports it and has the Themes service running), so I would certainly like it if it could fall back on some other default, but since I'm fairly sure 99% of my users will have it available, I'd like to make use of it if possible. Specifically, for newer Windows versions (Vista and 7), things like hyperlinks have a softer more pastel-ish blue. The old System Colors do not define anything for links and the like, and in general are much more limited (coming from the 95 days) in choices and variety. Though WPF probably has better support, I'm not at liberty to use it. If some third party utility, assembly, or the like is necessary, it would also need to be free to use. I don't need anything that fancy, but in a perfect world I would be able to do something like this: linkLabel1.LinkColor = System.Drawing.ThemeColors.Hyperlink; Am I stuck just using the default Blue (0,0,255) and having them look out of place in Vista and above? I'll even settle for ugly p/invoke interop methods if need be...

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  • Automating ftp command line application redirecting I/O in .Net

    - by SoMoS
    Hello, I'm trying to automate the ftp client that Windows includes redirecting the I/O from the process. What I'm doing is starting the process from my application and trying to read what the client prints on the screen and sending my commands to it. The problem is that I can not read almost any data sent by the ftp client. Some data is present but most data is not read. That's the code I have until now. Public Sub Start() process = New Diagnostics.Process() process.StartInfo.FileName = "ftp.exe" #'' The command is on the path process.StartInfo.CreateNoWindow = True process.StartInfo.RedirectStandardInput = True process.StartInfo.RedirectStandardOutput = True process.StartInfo.UseShellExecute = False process.Start() process.StandardInput.AutoFlush = True process.BeginOutputReadLine() End Sub #'' takes data from the stdout Private Sub process_OutputDataReceived(ByVal sender As Object, ByVal e As System.Diagnostics.DataReceivedEventArgs) Handles process.OutputDataReceived #'' At this moment here there is code to show the stdout at a textbox End Sub #'' sends data to stdin Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click process.StandardInput.WriteLine(Me.TextEdit1.Text) End Sub Now when I execute this for example and send ? I just get the first line (and I should get a lot more). Or when I send the open command I should receive an A but nothing is received. Any ideas? Another question is ... when a console applications writes on the screen it always does that by writing at the stdout or the stderr isn't it?

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  • Windows system monitoring and profiling

    - by Aris
    I have several dozen 64-bit Windows 2003 servers in a high performance environment with very bursty system utilization. I am looking for a tool (or tools) to monitor and analyze system performance (eg, CPU utilization, bandwidth, etc). This tool can either query servers from a central location (SNMP) or require installation of a component on each server. It should poll on a 1-second interval. It should be able to generate pretty graphs which show trends over time. As a nice-to-have, it should be able to send out emails or IMs when certain thresholds are exceeded. The tools I have investigated so far, including Solarwinds and PRTG, are not designed to poll this frequently. They seem to be designed for a ~30-second interval. Solarwinds wouldn't go lower than 3-sec, and PRTG chokes at 1-sec. They both default to 1-min. All three tools seem more focused on outage monitoring and reporting than metric collection. Given the bursty nature of our applications, such infrequent polling would result in a very inaccurate picture of performance. I am considering rolling my own solution using perfmon. This would be a lot of work, and seems like reinventing the wheel. Are there any tools out there that meet my needs?

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  • Coupling between controller and view

    - by cheez
    The litmus test for me for a good MVC implementation is how easy it is to swap out the view. I've always done this really badly due to being lazy but now I want to do it right. This is in C++ but it should apply equally to non-desktop applications, if I am to believe the hype. Here is one example: the application controller has to check some URL for existence in the background. It may connect to the "URL available" event (using Boost Signals) as follows: BackgroundUrlCheckerThread(Controller & controller) { // ... signalUrlAvailable.connect( boost::bind(&Controller::urlAvailable,&controller,_1)) } So what does Controller::urlAvailable look like? Here is one possibility: void Controller::urlAvailable(Url url) { if(!view->askUser("URL available, wanna download it?")) return; else // Download the url in a new thread, repeat } This, to me, seems like a gross coupling of the view and the controller. Such a coupling makes it impossible to implement the view when using the web (coroutines aside.) Another possibility: void Controller::urlAvailable(Url url) { urlAvailableSignal(url); // Now, any view interested can do what it wants } I'm partial to the latter but it appears that if I do this there will be: 40 billion such signals. The application controller can get huge for a non-trivial application A very real possibility that a given view accidentally ignores some signals (APIs can inform you at link-time, but signals/slots are run-time) Thanks in advance.

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  • How to best implement Version Control for Web Development?

    - by Adam Taylor
    Version control systems are obviously important in development projects but there use in web development projects appears to be more complex, what with the requirement of having a web server to run all but the simplest of web applications. With that in mind, I have looked around and discovered a few different methods of using version control in web development projects: Provide each developer with a virtual machine which is a replication of the development server and have the developer run their working copy of the application in the virtual machine. Have each developer use a sub domain on the development server, e.g. john.project.com and checkout their working copy of the app to the directories the sub domain points to. Use the version control system to checkout code, make a change, commit the code and then check it on the development server (which points to the head of the repository). I can see a drawback of 1 being the added time required to create the virtual machines and ensure that the virtual machines are kept insync with the development server (also the need(?) to continuously change the developers host file to point at the virtual machine not the development server). I can see 2 possibly being a problem if absolute URLs are used within the site unless there is an easy way to update the configuration to use the new subdomains as well. 3 is the easiest to set up but is rather primitive and it will presumably become quite tedious for a developer to keep checking in the code after every time change. How have the users of stackoverflow used version control with web development projects and which method/workflow was most effective. Please also include extra methods I haven't thought of / read about.

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  • Numeric Data Entry in WPF

    - by Matt Hamilton
    How are you handling the entry of numeric values in WPF applications? Without a NumericUpDown control, I've been using a TextBox and handling its PreviewKeyDown event with the code below, but it's pretty ugly. Has anyone found a more graceful way to get numeric data from the user without relying on a third-party control?private void NumericEditPreviewKeyDown(object sender, KeyEventArgs e) { bool isNumPadNumeric = (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9) || e.Key == Key.Decimal; bool isNumeric = (e.Key >= Key.D0 && e.Key <= Key.D9) || e.Key == Key.OemPeriod; if ((isNumeric || isNumPadNumeric) && Keyboard.Modifiers != ModifierKeys.None) { e.Handled = true; return; } bool isControl = ((Keyboard.Modifiers != ModifierKeys.None && Keyboard.Modifiers != ModifierKeys.Shift) || e.Key == Key.Back || e.Key == Key.Delete || e.Key == Key.Insert || e.Key == Key.Down || e.Key == Key.Left || e.Key == Key.Right || e.Key == Key.Up || e.Key == Key.Tab || e.Key == Key.PageDown || e.Key == Key.PageUp || e.Key == Key.Enter || e.Key == Key.Return || e.Key == Key.Escape || e.Key == Key.Home || e.Key == Key.End); e.Handled = !isControl && !isNumeric && !isNumPadNumeric; }

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  • How do I securely authenticate the calling assembly of a WCF service method?

    - by Tim
    The current situation is as follows: We have an production .net 3.5 WCF service, used by several applications throughout the organization, over wsHttpBinding or netTcpBinding. User authentication is being done on the Transport level, using Windows integrated security. This service has a method Foo(string parameter), which can only be called by members of given AD groups. The string parameter is obligatory. A new client application has come into play (.net 3.5, C# console app), which eliminates the necessity of the string parameter. However, only calls from this particular application should be allowed to omit the string parameter. The identity of the caller of the client application should still be known by the server because the AD group limitation still applies (ruling out impersonation on the client side). I found a way to pass on the "evidence" of the calling (strong-named) assembly in the message headers, but this method is clearly not secure because the "evidence" can easily be spoofed. Also, CAS (code access security) seems like a possible solution, but I can't seem to figure out how to make use of CAS in this particular scenario. Does anyone have a suggestion on how to solve this issue? Edit: I found another thread on this subject; apparently the conclusion there is that it is simply impossible to implement in a secure fashion.

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  • Coherent access to mainframe files from Win32 application and IBM RDZ/Eclipse?

    - by Ira Baxter
    I have a suite of tools for processing IBM COBOL source code; these tools are built as Win32 applications and talk to Windows (including network) files using traditional Windows file system calls (open, close, read, write) and work just fine, thank you. I'd like to integrate these with Eclipse; we understand how to get Eclipse to do UI for us we think. The problem is that Eclipse/RDZ users access mainframe files through some IBM magic. In How does RDZ access mainframe files I tried to understand how Eclipse accessed files on a mainframe. Apparantly Eclipse/RDZ has a secret filesystem access backdoor not available to normal mortals. At issue is how our tools, reading some Windows-accessible file (local disk file, NFS to mainframe, ...) can associate such files with the files that Eclipse can access or is using? Ideally we'd like UI-integrated versions of our tools take an Eclipse file-name string for a mainframe file, pass it to our Windows application to process, have the Windows application open/read/process the file, and return results associated with that file to the Eclipse UI. Is there a canonical file name path that would be used with mainframe NFS that would be equivalent to the name or access object the Eclipse RDZ used to access the same file? Are all operations doable internally by Eclipse, doable by the mainframe NFS [for instance, can NFS read/update an element in a partitioned data set? Can Eclipse RDZ? Does it matter?] Is the mainframe file access available to custom Java code running under Eclipse RDZ (e.g., equivalents of open/close/read/write based on filename/path/something?) If so, can somebody steer me towards documentation describing the access methods? Anybody else already solve this problem or have a good suggestion?

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  • PDF parsing file trailer

    - by Ralph
    It is not clear from the PDF ISO standard document (PDF32000-2008) whether a comment may follow the startxref keyword: startxref Byte_offset_of_last_cross-reference_section %%EOF The standard does seem to imply that comments may appear anywhere: 7.2.3 Comments Any occurrence of the PERCENT SIGN (25h) outside a string or stream introduces a comment. The comment consists of all characters after the PERCENT SIGN and up to but not including the end of the line, including regular, delimiter, SPACE (20h), and HORZONTAL TAB characters (09h). A conforming reader shall ignore comments, and treat them as single white-space characters. That is, a comment separates the token preceding it from the one following it. EXAMPLE The PDF fragment in this example is syntactically equivalent to just the tokens abc and 123. abc% comment ( /%) blah blah blah 123 Comments (other than the %PDF–n.m and %%EOF comments described in 7.5, "File Structure") have no semantics. They are not necessarily preserved by applications that edit PDF files. If they are allowed to appear after the startxref, parsing the file becomes more difficult because you do not know how far to back up from the %%EOF comment to start parsing to find the byte offset. Any ideas?

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  • Using R in Processing through rJava/JRI?

    - by tommy-o-dell
    Hi guys, Is it possible to run R in Processing through rJava/JRI? If I deployed a Processing app on the web, would the client need R on their system? I'm looking to create an interactive information dashboard that I can deploy on the web. It seems that Processing is probably my best bet for the interactive/web part of things. Unfortunately, it doesn't look like there are many math/stats functions built-in. And there aren't any libraries for plotting data either. I've been using R and gpplot2 for a few months and am thrilled (amazed) at how easily it manipulates and plots data. So I'm wondering now if can get the best of both worlds and run R through a Processing applet. From the JRI website: JRI is a Java/R Interface, which allows to run R inside Java applications as a single thread. Basically it loads R dynamic library into Java and provides a Java API to R functionality. It supports both simple calls to R functions and a full running REPL. In a sense JRI is the inverse of rJava and both can be combined (i.e. you can run R code inside JRI that calls back to the JVM via rJava). The JGR project makes the full use of both JRI and rJava to provide a full Java GUI for R. JRI uses native code, but it supports all platforms where Sun's Java (or compatible) is available, including Windows, Mac OS X, Sun and Linux (both 32-bit and 64-bit). Thanks for the advice :)

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  • iPhone offline reading

    - by Andy
    Hi, first of all - I am quite new to iPhone App development (3 months). I am working for a software company that offers a content management system. Our customers are for the main part publishing houses for magazines. They use our software to write articles to their homepages. Now we want to offer iPhone Applications to go with our cms. What I have accomplished so far is an RSS reader that shows newly published articles in a list view. The user selects one article and is redirected to a specially formatted detail view of this article. The next step is to add offline reading capabilities. I have searched the internet up and down but couldn't find anything like a best practice for that. I get it that there are two possibilities in general: Store the contents of the uiwebview locally on the iPhone/iPad (including css, images, js and so on). There would be the need to rework the basic html to use the downloaded css, images and js. Also I would have to somehow edit hyperlinks to following pages in multipage articles - Sounds like a lot of work ;) Create a PDF on the server side and download that to the mobile device. Rework the RSS Source to point to the locally saved pdf instead of the website on the server. My question is - what is the better way to go? Are there any downsides for either of the possibilities? Are there other (simple ;)) ways to implement offline reading features? Are there possibly any howto's that I could've missed? Thanks y'all!

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  • How have you successfully implemented MessageBox.Show() functionality in MVVM?

    - by Edward Tanguay
    I've got a WPF application which calls MessageBox.Show() way back in the ViewModel (to check if the user really wants to delete). This actually works, but goes against the grain of MVVM since the ViewModel should not explicitly determine what happens on the View. So now I am thinking how can I best implement the MessageBox.Show() functionality in my MVVM application, options: I could have a message with the text "Are you sure...?" along with two buttons Yes and No all in a Border in my XAML, and create a trigger on the template so that it is collapsed/visible based on a ViewModelProperty called AreYourSureDialogueBoxIsVisible, and then when I need this dialogue box, assign AreYourSureDialogueBoxIsVisible to "true", and also handle the two buttons via DelegateCommand back in my ViewModel. I could also somehow try to handle this with triggers in XAML so that the Delete button actually just makes some Border element appear with the message and buttons in it, and the Yes button did the actually deleting. Both solutions seem to be too complex for what used to be a couple lines of code with MessageBox.Show(). In what ways have you successfully implemented Dialogue Boxes in your MVVM applications?

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  • java distributed cache for low latency, high availability

    - by Shahbaz
    I've never used distributed caches/DHTs like memcached, jboss cache, ehcache, etc. I'm wondering which, if any, is appropriate for my use. First, I'm not doing web applications (as most of these project seem to be geared towards web apps). I write servers (Order Management Systems actually) for financial trading firms. The servers themselves are not too complicated. They need to receive information (market data, orders, executions, etc.) rout them to their destination while possibly transforming some of these messages. I am looking at these products to solve the following problems: * Safe repository of the state of the server. I'd rather build the logic of my application as a bunch of transformers (similar to Apache Camel) and store the state in a 'safe' place * This repository should be distributed: in case one of these data stores crashes, one or two more should be up and I should be able to switch to them seamlessly * This repository should be fast. Single digits milliseconds count here, in other words, systems which consume/process this data are automated systems, not humans clicking on links. This system needs to have high-throughput and low latency. By sending my data outside the process, I am necessarily slowing performance, but I am trying to balance absolute raw speed and absolute protection of data. * This repository should be safe. Similar to the point about several on-line backups, this system needs to write data to disk (potentially more than one disk). I'd really like to stop writing my own 'transaction servers.' Am I correct to be looking into projects such as jboss cache, ehcache, etc.? Thanks

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  • Displaying shifts on a timetable/calendar using C#

    - by Dave Peters
    I am very much a beginner and have experience of SQL and a tiny amount of VBA. What I am looking to do is create a tool to pull shift times from a database and to display them on a timetable/calendar. It will be part of a desktop application that the (very tech illiterate) end users will use to view and amend shift patterns. In essence it will be a grid with days on one axis and people on the other (I would however like to have the blocks proportional to shift length). In my mind it would potentially be a simple Gantt chart. All computing stuff I’ve learnt has been through trial and error and I want to use this project to get a much better understanding of C# as well as to get to the end product. I have been reading around for ways to tackle the problem and my issue is creating the timetable framework to which I will bind the data. I am using Visual Studio 2010 and SQL Server 2008 R2. Do you know of good resources which will either start me on the road to designing my own interface or give a basic framework I can adapt? All the resources I’ve found so far have been in different languages or for web based applications. Thank you for your time.

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  • Custom model validation of dependent properties using Data Annotations

    - by Darin Dimitrov
    Since now I've used the excellent FluentValidation library to validate my model classes. In web applications I use it in conjunction with the jquery.validate plugin to perform client side validation as well. One drawback is that much of the validation logic is repeated on the client side and is no longer centralized at a single place. For this reason I'm looking for an alternative. There are many examples out there showing the usage of data annotations to perform model validation. It looks very promising. One thing I couldn't find out is how to validate a property that depends on another property value. Let's take for example the following model: public class Event { [Required] public DateTime? StartDate { get; set; } [Required] public DateTime? EndDate { get; set; } } I would like to ensure that EndDate is greater than StartDate. I could write a custom validation attribute extending ValidationAttribute in order to perform custom validation logic. Unfortunately I couldn't find a way to obtain the model instance: public class CustomValidationAttribute : ValidationAttribute { public override bool IsValid(object value) { // value represents the property value on which this attribute is applied // but how to obtain the object instance to which this property belongs? return true; } } I found that the CustomValidationAttribute seems to do the job because it has this ValidationContext property that contains the object instance being validated. Unfortunately this attribute has been added only in .NET 4.0. So my question is: can I achieve the same functionality in .NET 3.5 SP1? UPDATE: It seems that FluentValidation already supports clientside validation and metadata in ASP.NET MVC 2. Still it would be good to know though if data annotations could be used to validate dependent properties.

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  • Which CEP product to start with?

    - by Andreas
    Hi, I want to learn more on how to build CEP based applications. So I looked around and found several products (overview found here: http://rulecore.com/CEPblog/?page_id=47). But as there are quite a few at the moment, I don't know which is the best to start with. And overall I just would consider the one available for free. The rest is a bit to expensive for just private use ;) Esper is for free, but without Esper studio it seems quite tedious to develop a cep app. Streambase offers a free trial, but I couldn't find out how long you can use this (if only for a month, no that helpful for longer research). Oracle CEP suite seems quite complete, but in the cep scene - as far as I can see - it is the least recognized compared to Esper or Streambase. So do you have any hints on what is the best way to start with cep development? Is it worth to spent time on working through the oracle documenation or is it better to start with Esper or Streambase? Cheers, Andreas

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