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• Portlet container like pluto or jetspeed on google app engine?

  - by Patrick Cornelissen

  I am trying to build something "portlet server"-ish on the google app engine. (as open source) I'd like to use the JSR168/286 standards, but I think that the restrictions of the app engine will make it somewhere between tricky and impossible. Has anyone tried to run jetspeed or an application that uses pluto internally on the google app engine? Based on my current knowledge of portlets and the google app engine I'm anticipating these problems: A war file with portlets is from the deployment standpoint more or less a complete webapp (yes, I know that it doesn't really work without a portal server). The war file may contain it's own web.xml etc. This makes deployment on the app engine rather difficult, because the apps are not visible to each other, so all portlet containing archives need to be included in the war file of the deployed "app engine based portal server". The "portlets" are (at least in liferay) started as permanent servlet processes, based on their portlet.xmls and web.xmls which is located in the same spot for every portlet archive that is loaded. I think this may be problematic in the app engine, because everything is in one big "web app", so it may be tricky to access the portlet.xmls from each archive. This prevents a 100% compatibility in my opinion. Is here anyone who has any experience with the combination of portlets and the app engine? Do you think it's feasible to modify jetspeed, pluto or any other portlet container to be able to run it on the app engine?

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• Date from String using NSDateFormatter regardless 12h-24h setting

  - by maxf99

  Hello everybody, Today my question is about date formats and strings. My application downloads some strings representing dates from the internet. The date format is always like this: "2010-05-24 at 20:45" I need to convert this string into an NSDate object in order to perform some date manipulations. I tried this code: NSString * dateString = @"2010-05-24 at 20:45" // actually downloaded from the internet NSDateFormatter * myDateFormatter = [[NSDateFormatter alloc] init]; [myDateFormatter setDateFormat:@"yyyy-MM-dd 'at' HH:mm"]; NSDate * dateFromString = [myDateFormatter dateFromString:dateString]; This seems to work perfectly fine as long as the iPhone is set to 24h clock. As long as I switch to 12h clock in the general settings the NSDate object is not created (and the application happily crashes) I have read others having similar problems but I don't seem to find a solution. Now the questions: It doesn't make sense to me that the NSDateFormatter is sensible to user settings as long as I am specifying which format it is supposed to use to parse the string (which is not modifiable because it comes from the web), what's the use of checking user settings? More important, how can I get my task performed (to get an NSDate object from the string regardless the user settings)?

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• Unresolved external symbol - MySQL API C++

  - by Zack_074

  Hey I've had nonstop problems with SQL. I'm trying to get some experience because I know it's a vital part of the industry. I got it working with C#, but now I'm working on connecting to a database in c++. I have the project properly linked and what not. Here's my code and the errors I'm getting. #include "stdafx.h" #include <mysql.h> #include <iostream> MYSQL mysql; MYSQL_RES result; using namespace std; int _tmain(int argc, _TCHAR* argv[]) { mysql_init(&mysql); if(!mysql_real_connect(&mysql, "localhost", "root", "angel552002", "MyDatabse", 0, NULL, 0)) { printf("Failed to connect"); } return 0; } and the errors: Error 1 error LNK2001: unresolved external symbol _mysql_real_connect@32 c:\Users\Zack-074\documents\visual studio 2010\Projects\MySql\MySql\MySql.obj Error 2 error LNK2001: unresolved external symbol _mysql_init@4 c:\Users\Zack-074\documents\visual studio 2010\Projects\MySql\MySql\MySql.obj Error 3 error LNK1120: 2 unresolved externals c:\users\zack-074\documents\visual studio 2010\Projects\MySql\Debug\MySql.exe 1 I really appreciate the help.

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• Stop IE users typing into the file upload input

  - by Dexter

  My testers have discovered that if you type free text into a file upload input then none of the buttons on the page work until that text is removed (so the page cannot be submitted). I am able to replicate this with the following ASPX code (with no code behind): <%@ Page Language="C#" AutoEventWireup="true" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <body> <form id="form1" runat="server"> <div> <asp:FileUpload ID="fuTest" runat="server" /> <asp:Button ID="btnSubmit" runat="server" Text="Submit" /> </div> </form> </body> </html> (Note that I haven't bound any handlers to the page; despite this, the page is submitted when the submit button is clicked only if no text is entered into the upload text box) Is there any way to prevent users from typing free text into a file upload control? It seems that this is only possible in IE - Firefox and Chrome natively prevent text from being entered into upload input fields. I've seen solutions elsewhere which suggest hiding input and replacing it with a label / button combo, but this seems like it might cause more problems and work inconsistently across browsers. Any thoughts?

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• 1D Function into 2D Function Interpolation

  - by Drazick

  Hello. I have a 1D function which I want to interpolate into 2D function. I know the function should have "Polar Symmetry". Hence I use the following code (Matlab Syntax): Assuming the 1D function is LSF of the length 15. [x, y] = meshgrid([-7:7]); r = sqrt(x.^2 + y.^2); PSF = interp1([-7:7], LSF, r(:)); % Sometimes using 'spline' option, same results. PSF = reshape(PSF, [7, 7]); I have few problems: 1. Got some overshoot at the edges (As there some Extrapolation). 2. Can't enforce some assumptions (Monotonic, Non Negative). Is there a better Interpolation method for those circumstances? I couldn't find "Lanczos" based interpolation I can use the same way as interp1 (For a certain vector of points, in "imresize" you can only set the length). Is there such function anywhere? Has anyone encountered a function which allows enforcing some assumptions (Monotonically Decreasing, Non Negative, etc..). Thanks.

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• Backwards compatibility when using Core Data

  - by Alex

  Could anybody shed some light as to why is my app crashing with the following error on iPhone OS 2.2.1 dyld: Symbol not found: _OBJC_CLASS_$_NSPredicate Referenced from: /var/mobile/Applications/456F243F-468A-4969-9BB7-A4DF993AE89C/AppName.app/AppName Expected in: /System/Library/Frameworks/Foundation.framework/Foundation I have weak linked CoreData.framework, and have the Base SDK set to 3.0 and Deployment Target set to SDK 2.2 The app already uses other 3.0 features when available and I did not have any problems with those. But apparently the backward-compatibility methods used for other features do not work with Core Data. The app crashes before app delegate's applicationDidFinishLaunching gets called. Here's the debugger log: [Session started at 2010-05-25 20:17:03 -0400.] GNU gdb 6.3.50-20050815 (Apple version gdb-1119) (Thu May 14 05:35:37 UTC 2009) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "--host=i386-apple-darwin --target=arm-apple-darwin".tty /dev/ttys001 Loading program into debugger… sharedlibrary apply-load-rules all warning: Unable to read symbols from "MessageUI" (not yet mapped into memory). warning: Unable to read symbols from "CoreData" (not yet mapped into memory). Program loaded. target remote-mobile /tmp/.XcodeGDBRemote-12038-42 Switching to remote-macosx protocol mem 0x1000 0x3fffffff cache mem 0x40000000 0xffffffff none mem 0x00000000 0x0fff none run Running… [Switching to thread 10755] [Switching to thread 10755] Re-enabling shared library breakpoint 1 Re-enabling shared library breakpoint 2 Re-enabling shared library breakpoint 3 Re-enabling shared library breakpoint 4 Re-enabling shared library breakpoint 5 (gdb) continue warning: Unable to read symbols for ""/Users/alex/iPhone Projects/AppName/build/Debug-iphoneos"/AppName.app/AppName" (file not found). dyld: Symbol not found: _OBJC_CLASS_$_NSPredicate Referenced from: /var/mobile/Applications/456F243F-468A-4969-9BB7-A4DF993AE89C/AppName.app/AppName Expected in: /System/Library/Frameworks/Foundation.framework/Foundation (gdb)

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• Creating Lotus Notes documents with specific created/modified/last accessed dates for testing

  - by Xolstice

  I'm currently writing an application that moves Notes documents between databases based on the amount of days that have elapsed from the creation/modified/last accessed dates. I would just like to get ideas on a simple and convenient way to create documents with specific dates, without having to change the time on the Domino server, so that I could test out my application. The best way I found so far was to create a local replica and change the system clock to the date I want. Unfortunately there are problems associated with this method. It does not work on the modified date - I'm not sure how it is getting the modified date information when the location is set to Island (Disconnected) - and it also changes the modified and last accessed dates when the documents are replicated to the server replica. Someone suggested trying to create a DXL of the document, modify the date time in the DXL file, then import it back into the database as a Notes document; but that does not work. It just takes on the date-time that it was created. Can anyone offer any other suggestions?

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• NSScrollView frame and flipped documentView

  - by StrAbZ

  Hi, I have problems with NSScrollView, It is not displayed the way I want. Yes I know there is a lot of post about it around the web, I need to override the isFlipped, in order to make it return YES, in my NSView subclass. Ok, it's done, so now, my scrollView scroll from top to bottom, and not in the reverse way, as it was before overriding isFlipped. But, this is the second part, my real problem, which I didn't found any answer on the web, how the hell I'm supposed to code, or create my view in interface builder, if everything is flipped? If I put something at the top, it is displayed a the bottom… do you have any magic trick to handle that? And my last problem, is the NSScrollView frame. before setting the documentView of my scroll view, everything is fine, the scrollView is displayed at the place I choose, but, when I set the document view, it looks like the scrollview frame looks bigger, so I have to resize it…. is this a normal behavior? Thank you very much.

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• How do you save images to a Blackberry device via HttpConnection?

  - by Kai

  My script fetches xml via httpConnection and saves to persistent store. No problems there. Then I loop through the saved data to compose a list of image url's to fetch via queue. Each of these requests calls the httpConnection thread as so ... public synchronized void run() { HttpConnection connection = (HttpConnection)Connector.open("http://www.somedomain.com/image1.jpg"); connection.setRequestMethod("GET"); String contentType = connection.getHeaderField("Content-type"); InputStream responseData = connection.openInputStream(); connection.close(); outputFinal(responseData, contentType); } public synchronized void outputFinal(InputStream result, String contentType) throws SAXException, ParserConfigurationException, IOException { if(contentType.startsWith("text/")) { // bunch of xml save code that works fine } else if(contentType.equals("image/png") || contentType.equals("image/jpeg") || contentType.equals("image/gif")) { // how to save images here? } else { //default } } What I can't find any good documentation on is how one would take the response data and save it to an image stored on the device. Maybe I just overlooked something very obvious. Any help is very appreciated. Thanks

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• Extracting [] elements from form collection - mvc - should use icollection but have mix of types

  - by bergin

  hi there. have looked at Phil Haacks project on books at http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx which has been useful, but I have a mix of data types. I use a modelview so that i can have a mix of objects, in this case: Order (ie order.id, order.date etc), Customer, SoilSamplingOrder and a list of SoilSamplingSubJobs which is like this [0].id, [0].field, [1].id, [1].field etc Perhaps I should be using ICollection instead of List? I had problems getting UpdateModel to work so I used an extract from collection method. the first 4 method calls : orderRepository.FindOrder(id); etc give the model the original to be edited. but after this point i'm a little lost in how to update the subjobs. I hope i have delineated enough to make sense of the problem. [HttpPost] public ActionResult Edit(int id, FormCollection collection) { Order order = orderRepository.FindOrder(id); Customer cust = orderRepository.FindCustomer(order.customer_id); IList<SoilSamplingSubJob> sssj = orderRepository.FindSubOrders(id); SoilSamplingOrder sso = orderRepository.FindSoilSampleOrder(id); try { UpdateModel(order, collection.ToValueProvider()); UpdateModel(cust, collection.ToValueProvider()); UpdateModel(sso, collection.ToValueProvider()); IList<SoilSamplingSubJob> sssjs = orderRepository.extractSSSJ(collection); foreach (var sj in sssjs) UpdateModel(sso, collection.ToValueProvider()); orderRepository.Save(); return RedirectToAction("Details", new { id=order.order_id}); } catch { return View(); } }

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• Sending mail issues. very confusing

  - by Dejan.S

  Hi my name is what, my name is who.. ops got carried away Now this might be a serverfault question and a stackoverflow question but I will go with it here because I don't really know the answer. I been sending mail a lot with asp.net before and never had problems like this before. I have setup a mail with this following code var list = new List<string> { "mail", "mail", "mail", "mail" }; var smtp = new SmtpClient("localhost", 25); var plainText = txtPlain.Text; var htmlText = Server.HtmlDecode(FCKeditor1.Value); foreach (var email in list) { var message = new MailMessage() { From = new MailAddress("my server mail"), ReplyTo = new MailAddress("mail") }; var mailMessage = Server.HtmlDecode(FCKeditor1.Value); message.To.Add(email); message.Subject = "Hi Enzorit"; message.Body = mailMessage; message.IsBodyHtml = true; message.BodyEncoding = System.Text.Encoding.GetEncoding("iso-8859-2"); var alternateViewHtml = AlternateView.CreateAlternateViewFromString(htmlText, null, MediaTypeNames.Text.Html); var alternateViewPlainText = AlternateView.CreateAlternateViewFromString(plainText, null, MediaTypeNames.Text.Plain); message.AlternateViews.Add(alternateViewHtml); message.AlternateViews.Add(alternateViewPlainText); smtp.Send(message); } now the issue becomes that some email clients get just plain while some get the html. Like on my hotmail on the computer i get the html but on my iphone i get the plain one. Why is that? and like that wasn't enough The mail wont deliver to some mails like any .pl email. Now here is where I am thinking that it might be a reverse DNS setup thing on my windows server 2008 issue + some company mails, it becomes spam, i had same issue with hotmail but that was solved when I added the plain. Anybody have had the problem before? I am very thankful for any answer I get.. thanks

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• using JQuery and Prototype in the same page

  - by Don

  Hi, Several of my pages use both JQuery and Protoype. Since I upgraded to version 1.3 of JQuery this appears to be causing problems, because both libraries define a function named '$'. JQuery provides a function noConflict() which relinquishes control of $ to other libraries that may be using it. So it seems like I need to go through all my pages that look like this: <head> <script type="text/javascript" src="/obp/js/prototype.js"></script> <script type="text/javascript" src="/obp/js/jquery.js"></script> </head> and change them to look like this: <head> <script type="text/javascript" src="/obp/js/prototype.js"></script> <script type="text/javascript" src="/obp/js/jquery.js"></script> <script type="text/javascript"> jQuery.noConflict(); var $j = jQuery; </script> </head> I should then be able to use '$' for Prototype and '$j' (or 'jQuery') for JQuery. I'm not entirely happy about duplicating these 2 lines of code in every relevant page, and expect that at some point somebody is likely to forget to add them to a new page. I'd prefer to be able to do the following Create a file jquery-noconflict.js which "includes" jquery.js and the 2 lines of code shown above Import jquery-noconflict.js (instead of jquery.js) in all my JSP/HTML pages However, I'm not sure if it's possible to include one JS file in another, in the manner I've described? Of course an alternate solution is simply to add the 2 lines of code above to jquery.js directly, but if I do that I'll need to remember to do it every time I upgrade JQuery. Thanks in advance, Don

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• detecting double free object, release or not release ...

  - by mongeta

  Hello, If we have this code in our interface .h file: NSString *fieldNameToStoreModel; NSFetchedResultsController *fetchedResultsController; NSManagedObjectContext *managedObjectContext; DataEntered *dataEntered; In our implementation file .m we must have: - (void)dealloc { [fieldNameToStoreModel release]; [fetchedResultsController release]; [managedObjectContext release]; [dataEntered release]; [super dealloc]; } The 4 objects are assigned from a previous UIViewController, like this: UIViewController *detailViewController; detailViewController = [[CarModelSelectViewController alloc] initWithStyle:UITableViewStylePlain]; ((CarModelSelectViewController *)detailViewController).dataEntered = self.dataEntered; ((CarModelSelectViewController *)detailViewController).managedObjectContext = self.managedObjectContext; ((CarModelSelectViewController *)detailViewController).fieldNameToStoreModel = self.fieldNameToStoreModel; [self.navigationController pushViewController:detailViewController animated:YES]; [detailViewController release]; The objects that now live in the new UIViewController, are the same as the previous UIViewController, and I can't release them in the new UIViewController ? The problems is that sometimes, my app crashes when I leave the new UIViewController and go to the previous one, not always. Normally the error that I'm getting is a double free object. I've used the malloc_error_break but I'm still not sure wich object is. Sometimes I can go from the previous UIViewController to the next one and come back 4 or 5 times, and the double free object appears. If I don't release any object, all is working and Instruments says that there are no memory leaks ... So, the final question, should I release those objects here or not ? Thanks, m.

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• Which technology is best suited to store and query a huge readonly graph?

  - by asmaier

  I have a huge directed graph: It consists of 1.6 million nodes and 30 million edges. I want the users to be able to find all the shortest connections (including incoming and outgoing edges) between two nodes of the graph (via a web interface). At the moment I have stored the graph in a PostgreSQL database. But that solution is not very efficient and elegant, I basically need to store all the edges of the graph twice (see my question PostgreSQL: How to optimize my database for storing and querying a huge graph). It was suggested to me to use a GraphDB like neo4j or AllegroGraph. However the free version of AllegroGraph is limited to 50 million nodes and also has a very high-level API (RDF), which seems too powerful and complex for my problem. Neo4j on the other hand has only a very low level API (and the python interface is not mature yet). Both of them seem to be more suited for problems, where nodes and edges are frequently added or removed to a graph. For a simple search on a graph, these GraphDBs seem to be too complex. One idea I had would be to "misuse" a search engine like Lucene for the job, since I'm basically only searching connections in a graph. Another idea would be, to have a server process, storing the whole graph (500MB to 1GB) in memory. The clients could then query the server process and could transverse the graph very quickly, since the graph is stored in memory. Is there an easy possibility to write such a server (preferably in Python) using some existing framework? Which technology would you use to store and query such a huge readonly graph?

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• What are the specific names for these OLE controls?

  - by Kris

  I have been working on making a block of code that would enable me to input values into a worksheet, as well as an MSgraph object. I have succeeded in this, but this has just presented me with a new set of problems: What are the control names for changing the visible size as well as the focus of a worksheet? What are the control names for changing/making background colours and borders? How do I create and define new worksheets and MSGraph objects inside the document? My example code so far: Option Explicit Dim objWord 'Word application object Dim objIShape 'Inline shapes object Dim objOLE 'OLE object Set objWord=CreateObject("Word.Application") objWord.Application.Documents.Open("C:\birdy.doc") objWord.Visible=True Set objIShape = objWord.ActiveDocument.InlineShapes Function count_filled_spaces(intOLENo, strRange) 'Activates the the inline shape by number(intOLENo) and defines it as the OLE object objIShape(intOLENo).OLEFormat.Activate Set objOLE = objIShape(intOLENo).OLEFormat.Object 'Detects the ClassType of the inline shape and uses a class specific counter to count which datafields have data Dim strClass, i, p, intSheetno intSheetno = 1 strClass = objIShape(intOLENo).OLEFormat.ClassType i = 0 If Left(strClass, 8) = "MSGraph." then For Each p In objOLE.Application.DataSheet.Range(strRange) If p <> "" Then i = i+1 End If Next ElseIf Left(strClass, 6) = "Excel." then For Each p In objOLE.Worksheets(intSheetno).Range(strRange) If p <> "" Then i = i+1 End If Next objOLE.Worksheets(intSheetno).Range("B" & i+1) = objOLE.Worksheets(intSheetno).Range("B" & i) End if count_filled_spaces = i End Function Dim strRange strRange = InputBox("Lol", "do eeet", "B1:B10") wscript.echo count_filled_spaces(2, strRange) 'objWord.Application.Documents.Save 'objWord.Application.Documents.Close 'objWord.Application.Quit WScript.Quit(0)

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• When should I be cautious using about data binding in .NET?

  - by Ben McCormack

  I just started working on a small team of .NET programmers about a month ago and recently got in a discussion with our team lead regarding why we don't use databinding at all in our code. Every time we work with a data grid, we iterate through a data table and populate the grid row by row; the code usually looks something like this: Dim dt as DataTable = FuncLib.GetData("spGetTheData ...") Dim i As Integer For i = 0 To dt.Rows.Length - 1 '(not sure why we do not use a for each here)' gridRow = grid.Rows.Add() gridRow(constantProductID).Value = dt("ProductID").Value gridRow(constantProductDesc).Value = dt("ProductDescription").Value Next '(I am probably missing something in the code, but that is basically it)' Our team lead was saying that he got burned using data binding when working with Sheridan Grid controls, VB6, and ADO recordsets back in the nineties. He's not sure what the exact problem was, but he remembers that binding didn't work as expected and caused him some major problems. Since then, they haven't trusted data binding and load the data for all their controls by hand. The reason the conversation even came up was because I found data binding to be very simple and really liked separating the data presentation (in this case, the data grid) from the in-memory data source (in this case, the data table). "Loading" the data row by row into the grid seemed to break this distinction. I also observed that with the advent of XAML in WPF and Silverlight, data-binding seems like a must-have in order to be able to cleanly wire up a designer's XAML code with your data. When should I be cautious of using data-binding in .NET?

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• Fulltext search on many tables

  - by Rob

  I have three tables, all of which have a column with a fulltext index. The user will enter search terms into a single text box, and then all three tables will be searched. This is better explained with an example: documents doc_id name FULLTEXT table2 id doc_id a_field FULLTEXT table3 id doc_id another_field FULLTEXT (I realise this looks stupid but that's because I've removed all the other fields and tables to simplify it). So basically I want to do a fulltext search on name, a_field and another_field, and then show the results as a list of documents, preferably with what caused that document to be found, e.g. if another_field matched, I would display what another_field is. I began working on a system whereby three fulltext search queries are performed and the results inserted into a table with a structure like: search_results table_name row_id score (This could later be made to cache results for a few days with e.g. a hash of the search terms). This idea has two problems. The first is that the same document can be in the search results up to three times with different scores. Instead of that, if the search term is matched in two tables, it should have one result, but a higher score. The second is that parsing the results is difficult. I want to display a list of documents, but I don't immediately know the doc_id without a join of some kind; however the table to join to is dependant on the table_name column, and I'm not sure how to accomplish that. Wanting to search multiple related tables like this must be a common thing, so I guess what I'm asking is am I approaching this in the right way? Can someone tell me the best way of doing it please.

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• iOS 5 Audio Alarms Don't Sound Without kAudioSessionProperty_OverrideCategoryMixWithOthers On

  - by coneybeare

  I have an audio app that is having some problems with the way iOS 5 has changed audio behaviors. When my app's audio is playing (AVAudioSessionCategoryPlayback), and a Clock.app alarm or timer is fired from the OS, the UIAlertView notification pops up, but without the audio alert. My application sound ducks fine to get out of the way of the audio alert, but the alarm app's audio alert does not sound. Naturally, tons of support requests poured in over the iOS 5 change. I have solved this temporarily by setting kAudioSessionProperty_OverrideCategoryMixWithOthers which lets the alarm audio come through, but there are a few very undesirable side-effects when doing this: Other app's audio can play with/over mine. The remote control events are not routed to my app, but to iPod.app. None of the above drawbacks are acceptable for my app's requirements. I have been hacking away at this for some time now but haven't been able to crack it. How can I setup my audio such that: My app's audio still uses the AVAudioSessionCategoryPlayback category for background audio. The Clock.app alarms still have their audio alerts make sound The app still responds to remote control notifications

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• Synchronizing ASP.NET MVC action methods with ReaderWriterLockSlim

  - by James D

  Any obvious issues/problems/gotchas with synchronizing access (in an ASP.NET MVC blogging engine) to a shared object model (NHibernate, but it could be anything) at the Controller/Action level via ReaderWriterLockSlim? (Assume the object model is very large and expensive to build per-request, so we need to share it among requests.) Here's how a typical "Read Post" action would look. Enter the read lock, do some work, exit the read lock. public ActionResult ReadPost(int id) { // ReaderWriterLockSlim allows multiple concurrent writes; this method // only blocks in the unlikely event that some other client is currently // writing to the model, which would only happen if a comment were being // submitted or a new post were being saved. _lock.EnterReadLock(); try { // Access the model, fetch the post with specificied id // Pseudocode, etc. Post p = TheObjectModel.GetPostByID(id); ActionResult ar = View(p); return ar; } finally { // Under all code paths, we must release the read lock _lock.ExitReadLock(); } } Meanwhile, if a user submits a comment or an author authors a new post, they're going to need write access to the model, which is done roughly like so: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveComment(/* some posted data */) { // try/finally omitted for brevity _lock.EnterWriteLock(); // Save the comment to the DB, update the model to include the comment, etc. _lock.ExitWriteLock(); } Of course, this could also be done by tagging those action methods with some sort of "synchronized" attribute... but however you do it, my question is is this a bad idea? ps. ReaderWriterLockSlim is optimized for multiple concurrent reads, and only blocks if the write lock is held. Since writes are so infrequent (1000s or 10,000s or 100,000s of reads for every 1 write), and since they're of such a short duration, the effect is that the model is synchronized , and almost nobody ever locks, and if they do, it's not for very long.

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• Better ways to implement a modulo operation (algorithm question)

  - by ryxxui

  I've been trying to implement a modular exponentiator recently. I'm writing the code in VHDL, but I'm looking for advice of a more algorithmic nature. The main component of the modular exponentiator is a modular multiplier which I also have to implement myself. I haven't had any problems with the multiplication algorithm- it's just adding and shifting and I've done a good job of figuring out what all of my variables mean so that I can multiply in a pretty reasonable amount of time. The problem that I'm having is with implementing the modulus operation in the multiplier. I know that performing repeated subtractions will work, but it will also be slow. I found out that I could shift the modulus to effectively subtract large multiples of the modulus but I think there might still be better ways to do this. The algorithm that I'm using works something like this (weird pseudocode follows): result,modulus : integer (n bits) (previously defined) shiftcount : integer (initialized to zero) while( (modulus<result) and (modulus(n-1) != 1) ){ modulus = modulus << 1 shiftcount++ } for(i=shiftcount;i>=0;i++){ if(modulus<result){result = result-modulus} if(i!=0){modulus = modulus << 1} } So...is this a good algorithm, or at least a good place to start? Wikipedia doesn't really discuss algorithms for implementing the modulo operation, and whenever I try to search elsewhere I find really interesting but incredibly complicated (and often unrelated) research papers and publications. If there's an obvious way to implement this that I'm not seeing, I'd really appreciate some feedback.

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• CSRF Protection in AJAX Requests using MVC2

  - by mnemosyn

  The page I'm building depends heavily on AJAX. Basically, there is just one "page" and every data transfer is handled via AJAX. Since overoptimistic caching on the browser side leads to strange problems (data not reloaded), I have to perform all requests (also reads) using POST - that forces a reload. Now I want to prevent the page against CSRF. With form submission, using Html.AntiForgeryToken() works neatly, but in AJAX-request, I guess I will have to append the token manually? Is there anything out-of-the box available? My current attempt looks like this: I'd love to reuse the existing magic. However, HtmlHelper.GetAntiForgeryTokenAndSetCookie is private and I don't want to hack around in MVC. The other option is to write an extension like public static string PlainAntiForgeryToken(this HtmlHelper helper) { // extract the actual field value from the hidden input return helper.AntiForgeryToken().DoSomeHackyStringActions(); } which is somewhat hacky and leaves the bigger problem unsolved: How to verify that token? The default verification implementation is internal and hard-coded against using form fields. I tried to write a slightly modified ValidateAntiForgeryTokenAttribute, but it uses an AntiForgeryDataSerializer which is private and I really didn't want to copy that, too. At this point it seems to be easier to come up with a homegrown solution, but that is really duplicate code. Any suggestions how to do this the smart way? Am I missing something completely obvious?

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• Generics with constraints hierarchy

  - by devoured elysium

  I am currently facing a very disturbing problem: interface IStateSpace<Position, Value> where Position : IPosition // <-- Problem starts here where Value : IValue // <-- and here as I don't { // know how to get away this // circular dependency! // Notice how I should be // defining generics parameters // here but I can't! Value GetStateAt(Position position); void SetStateAt(Position position, State state); } As you'll down here, both IPosition, IValue and IState depend on each other. How am I supposed to get away with this? I can't think of any other design that will circumvent this circular dependency and still describes exactly what I want to do! interface IState<StateSpace, Value> where StateSpace : IStateSpace where Value : IValue { StateSpace StateSpace { get; }; Value Value { get; set; } } interface IPosition { } interface IValue<State> where State : IState { State State { get; } } Basically I have a state space IStateSpace that has states IState inside. Their position in the state space is given by an IPosition. Each state then has one (or more) values IValue. I am simplifying the hierarchy, as it's a bit more complex than described. The idea of having this hierarchy defined with generics is to allow for different implementations of the same concepts (an IStateSpace will be implemented both as a matrix as an graph, etc). Would can I get away with this? How do you generally solve this kind of problems? Which kind of designs are used in these cases? Thanks

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• Does this use of Monitor.Wait/Pulse have a race condition?

  - by jw

  I have a simple producer/consumer scenario, where there is only ever a single item being produced/consumed. Also, the producer waits for the worker thread to finish before continuing. I realize that kind of obviates the whole point of multithreading, but please just assume it really needs to be this way (: This code doesn't compile, but I hope you get the idea: // m_data is initially null // This could be called by any number of producer threads simultaneously void SetData(object foo) { lock(x) // Line A { assert(m_data == null); m_data = foo; Monitor.Pulse(x) // Line B while(m_data != null) Monitor.Wait(x) // Line C } } // This is only ever called by a single worker thread void UseData() { lock(x) // Line D { while(m_data == null) Monitor.Wait(x) // Line E // here, do something with m_data m_data = null; Monitor.Pulse(x) // Line F } } Here is the situation that I am not sure about: Suppose many threads call SetData() with different inputs. Only one of them will get inside the lock, and the rest will be blocked on Line A. Suppose the one that got inside the lock sets m_data and makes its way to Line C. Question: Could the Wait() on Line C allow another thread at Line A to obtain the lock and overwrite m_data before the worker thread even gets to it? Supposing that doesn't happen, and the worker thread processes the original m_data, and eventually makes its way to Line F, what happens when that Pulse() goes off? Will only the thread waiting on Line C be able to get the lock? Or will it be competing with all the other threads waiting on Line A as well? Essentially, I want to know if Pulse()/Wait() communicate with each other specially "under the hood" or if they are on the same level with lock(). The solution to these problems, if they exist, is obvious of course - just surround SetData() with another lock - say, lock(y). I'm just curious if it's even an issue to begin with.

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• How to propagate .java file change to .class under eclipse, tomcat & stripes

  - by BigBourin

  Hi, i'm new to java and i got some problems. i'm developping a web application using the framework stripes on tomcat 6.0. I'm working with eclipse EE on windows. i successfully managed to get the stripes example application (called Bugzooky) up and running on my tomcat server. I imported the .war file and stripes libs in Eclipse. Here is the stripes archive containing the examples and libs But now i'm trying to change the example source files to learn how does it work. but whatever the modification made to the source files "WebContent/WEB-INF/src/*.java", nothing change! even after restarting the server. i noticed that the classes are compiled into .class files in the "ImportedClasses" folder, and tomcat always use these files, they are never updated, and if i removed one of them, the application just don't start. it look like my source files don't exists! I also tried to build my webapp from scratch, but when i tried to use the features used in the example files (like SecurityFilter.java): import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import ... It ends up with plenty of: the import javax.servlet.Filter cannot be resolved I checked the Librairies and it look like i'm using exactly the same as the example. It's probably something i didn't understood about java but i googled 100 times yesterday, and i can't find the solution (i probably didn't search the right place because i don't really understand my problem). I hope you'll be able to help me.

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• Place Query Results into Array then Implode?

  - by jason

  Basically I pull an Id from table1, use that id to find a site id in table2, then need to use the site ids in an array, implode, and query table3 for site names. I cannot implode the array correctly first I got an error, then used a while loop. With the while loop the output simply says: Array $mysqli = mysqli_connect("server", "login", "pass", "db"); $sql = "SELECT MarketID FROM marketdates WHERE Date = '2010-04-04 00:00:00' AND VenueID = '2'"; $result = mysqli_query($mysqli, $sql) or die(mysqli_error($mysqli)); $dates_id = mysqli_fetch_assoc ( $result ); $comma_separated = implode(",", $dates_id); echo $comma_separated; //This Returns 79, which is correct. $sql = "SELECT SIteID FROM bookings WHERE BSH_ID = '1' AND MarketID = '$comma_separated'"; $result = mysqli_query($mysqli, $sql) or die(mysqli_error($mysqli)); // This is where my problems start $SIteID = array(); while ($newArray = mysqli_fetch_array($result, MYSQLI_ASSOC)) { $SIteID[] = $newArray[SIteID]; } $locationList = implode(",",$SIteID); ?> Basically what I need to do is correctly move the query results to an array that I can implode and use in a 3rd query to pull names from table3.

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