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• SIGABRT on iPhone when changing xib

  - by Boz

  I've just finished off an app for the iPhone which, until today, ran fine on the iPhone simulator and actual devices. I tried changing the xib which is loaded in the applicationDidFinishLaunching method in my application delegate class - all I did was change the string in initWithNibName. When I launch the app on the simulator, the Default.png image is shown, then the app crashes with an uncaught exception. When running on a device, the Default.png image is shown for about 10 seconds, the UI is never loaded and I get 'GDB: Program received signal: "SIGABRT".' on the Xcode status bar. Debugging shows that applicationDidFinishLaunching is never actually reached before the app crashes. Setting the starting xib back to the original solves the issue, but now I've made a change and saved it in the Interface Builder and the app shows the same issues as above - I've made no code changes at all. Is this a memory issue, or a known issue of a common mistake? NOTE: I've made no code changes whatsoever, and the only changes I've made to the xib are cosmetic, the IBOutlets are all intact.

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• I'm having trouble spacing a menu control in an ASP.NET page. Is my solution the correct way to do t

  - by pkiyan

  Hey, I added a menu control to my page that is displayed vertically. I couldn't find a way to add spaces (I'd like about 5px.) between the menu items, so I just did something similar to this: <asp:Menu ID="Menu1" runat="server" BackColor="ActiveBorder"> <Items> <asp:MenuItem NavigateUrl="~/About.aspx" Text="One" /> </Items> </asp:Menu> <p></p> <asp:Menu ID="Menu2" runat="server" BackColor="ActiveBorder"> <Items> <asp:MenuItem NavigateUrl="~/Default.aspx" Text="Two" /> </Items> </asp:Menu> I just created multiple menu controls with a single menu item control in them, and placed a break between the menu controls. This seems very wrong to me, but I could not figure out another way. Also, this is a bit off subject, but is it okay to use empty paragraph tags as line breaks?(sometimes a br tag is too much) Thanks..

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• AI navigation around a 2d map - Avoiding obstacles.

  - by Curt Walker

  Hey there, I know my question seems pretty vague but I can't think of a better way to put it so I'll start off by explaining what I'm trying to do. I'm currently working on a project whereby I've been given a map and I'm coding a 'Critter' that should be able to navigate it's way around the map, the critter has various other functions but are not relevant to the current question. The whole program and solution is being written in C#. I can control the speed of the critter, and retrieve it's current location on the map by returning it's current X and Y position, I can also set it's direction when it collides with the terrain that blocks it. The only problem I have is that I can't think of a way to intelligently navigate my way around the map, so far I've been basing it around what direction the critter is facing when it collides with the terrain, and this is in no way a good way of moving around the map! I'm not a games programmer, and this is for a software assignment, so I have no clue on AI techniques. All I am after is a push in the right direction on how I could go about getting this critter to find it's way around any map given to me. Here's an image of the map and critters to give you an idea of what i'm talking about. Here's a link to an image of what the maps and critters look like. Map and Critter image I'm in no way looking for anyone to give me a full solution, just a push in the general direction on map navigation. Thanks in advance!

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• SSIS Transaction with Sql Transaction

  - by Mike

  I started with a package to make sure Transactions are working correctly. The package level transaction is set to Required. I have two Execute Sql Task, one deletes rows from a table and one does 1/0, to throw the error. Both task are set to supported transaction level and Serializable IsolationLevel. That works. Now when I replace my two sql task to two separate procedure calls, the first one, ChargeInterest, runs successful but the second one, PaymentProcess, fails always saying. [Execute SQL Task] Error: Executing the query "Exec [proc_xx_NotesReceivable_PaymentProcess] ..." failed with the following error: "Uncommittable transaction is detected at the end of the batch. The transaction is rolled back.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly. PaymentProcess being the second stored procedure. Both procedures have there own BEGIN, COMMIT AND ROLLBACKS inside the SP. I believe that the transactions are being successfully handed in the Charge Interest because I can run the following without issues or the dreaded you started with 0 and now have 1 transaction. EXEC [proc_XX_NotesReceivable_ChargeInterest] 'NR', 'M', 186, 300 EXEC [proc_XX_NotesReceivable_PaymentProcess] 'NR', 186, 300 --OR GO BEGIN TRAN EXEC [proc_XX_NotesReceivable_ChargeInterest] 'NR', 'M', 186, 300 EXEC [proc_XX_NotesReceivable_PaymentProcess] 'NR', 186, 300 ROLLBACK TRAN Now I have noticed that DTC does get kicked off in both instances? Why I am not sure because it is using the same connection. In the live example I can see the transaction get started but disappears if I put a breakpoint on the PreExecute event of the second stored procedure. What is the correct way to mingle SP transactions with SSIS transactions?

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• [iText] Inserting Image onCloseDocument

  - by David

  I'm trying to insert an image in the footer of my document using iText's onCloseDocument event. I have the following code: public void onCloseDocument(PdfWriter writer, Document document) { PdfContentByte pdfByte = writer.getDirectContent(); try { // logo is a non-null global variable Image theImage = new Jpeg(logo); pdfByte.addImage(theImage, 400.0f, 0.0f, 0.0f, 400.0f, 0.0f, 0.0f); } catch (Exception e) { e.printStackTrace(); } } The code throws no exceptions, but it also fails to insert the image. This identical code is used onOpenDocument to insert the same logo. The only difference between the two methods are the coordinates in pdfByte.addImage. However, I've tried quite a few different coordinations in onCloseDocument and none of them appear anywhere in my document. Is there any troubleshooting technique for detecting content which is displayed off-page in a PDF? If not, can anyone see the problem with my onCloseDocument method? Edit: As a followup, it seems that onDocumentClose puts its content on page document.length() + 1 (according to its API). However, I don't know how to change the page number back to document.length() and place my logo on the last page.

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• Strategy for animating a lot of "LED's" - thread?, UIView animations? NSOperation? (iPhone)

  - by RickiG

  Hi I have to do some different views containing 72 LED lights. I built an LED Class so I can loop through the LED's and set them to different colors (Green, Red, Orange, Blue None etc.). The LED then loads the appropriate .png. This works fine, I loop over the LED's and set them. Now I know that at some time they will need to not just turn on/off change color, but will have to turn on with a small delay. Like an equalizer. I have a 5-10 views containing the 72 LED's and I would like to achieve the above with the minimum amount of memory/CPU strain. for(LED *l in self.ledArray) { [l display:Green]; } I simply loop as shown above and inside the LED is a switch case that does the correct logic. If this were actual LED's and a microController I would use sleep(100) or similar in the loop, but I would really like to avoid stuff like that for obvious reasons. I was thinking that doing a performOnThread withDelay would really be consuming, so would UIView animation changing the alpha and NSOperation would also be a lot of lifting for a small feature. Is there a both efficient and clever way to go around this? Thanks for any inspiration given:)

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• Need some ignition in Embedded Systems

  - by Rahul

  I'm very much interested in building applications for Embedded Devices. I'm in my 3rd year Electrical Engineering and I'm passionate about coding, algorithms, Linux OS, etc. And also by Googling I found out that Linux OS is one of the best OSes for Embedded devices(may be/may not be). I want to work for companies which work on mobile applications. I'm a newbie/naive to this domain & my skills include C/C++ & MySQL. I need help to get started in the domain of Embedded Systems; like how/where to start off, Hardware prerequisites, necessary programming skills, also what kind of Embedded Applications etc. I've heard of ARM, firmware, PIC Micorcontrollers; but I don't know anything & just need proper introduction about them. Thanx. P.S: I'm currently reading Bjarne Struotsup's lecture in C++ at Texas A&M University, and one chapter in it describes about Embedded Systems Programming.

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• Show/hide text based on optgroup selection using Jquery

  - by general exception

  I have the following HTML markup:- <select name="Fault" class="textbox" id="fault"> <option>Single Light Out</option> <option>Light Dim</option> <option>Light On In Daytime</option> <option>Erratic Operating Times</option> <option>Flashing/Flickering</option> <option>Causing Tv/Radio Interference</option> <option>Obscured By Hedge/Tree Branches</option> <option>Bracket Arm Needs Realigning</option> <option>Shade/Cover Missing</option> <option>Column In Poor Condition</option> <option>Several Lights Out (please state how many)</option> <option>Column Leaning</option> <option>Door Missing/Wires Exposed</option> <option>Column Knocked Down/Traffic Accident</option> <option>Lantern Or Bracket Broken Off/Hanging On Wires</option> <option>Shade/Cover Hanging Open</option> </select> <span id="faulttext" style="color:Red; display:none">Text in the span</span> This Jquery snippet adds the last 5 options into an option group. $('#fault option:nth-child(n+12)').wrapAll('<optgroup label="Urgent Reasons">'); What I want to do is, remove the display:none if any of the items within the <optgroup> are selected, effectively displaying the span message, possibly with a fade in transition, and also hide the message if any options outside of the <optgroup> are selected.

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• help with mysql triggers (checking values before insert)

  - by user332817

  hi I'm quite new to mysql and I'm trying to figure out how to use triggers. what I'm trying to do: I have 2 tables, max and sub_max, when I insert a new row to sub_max I want to check if the SUM of the values with the same foreign_key as the new row are less than the value in the max table. I think this sounds confusing so here are my tables: CREATE TABLE max( number INT , MaxAmount integer NOT NULL) CREATE TABLE sub_max( sub_number INT , sub_MaxAmount integer NOT NULL, number INT, FOREIGN KEY ( number ) REFERENCES max( number )) and here is my code for the trigger, I know the syntax is off but this is the best I could do from looking up tutorials. CREATE TRIGGER maxallowed after insert on submax FOR EACH ROW BEGIN DECLARE submax integer; DECLARE maxmax integer; submax = select sum(sub_MaxAmount) from sub_max where sub_number = new.sub_number; submax = submax + new. sub_MaxAmount; maxmax = select MaxAmount from max where number = new.number ; if max>maxmax rollback? END I wanted to know if I'm doing this remotely correctly. Thanks in advance.

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• When is a good time to start thinking about scaling?

  - by Slokun

  I've been designing a site over the past couple days, and been doing some research into different aspects of scaling a site horizontally. If things go as planned, in a few months (years?) I know I'd need to worry about scaling the site up and out, since the resources it would end up consuming would be huge. So, this got me to thinking, when is the best time to start thinking about, and designing for, scalability? If you start too early on, you could easily over complicate your design, and make it impossible to actually build. You could also get too caught up in the details, the architecture, whatever, and wind up getting nothing done. Also, if you do get it working, but the site never takes off, you may have wasted a good chunk of extra effort. On the other hand, you could be saving yourself a ton of effort down the road. Designing it from the ground up to be big would make it much easier later on to let it grow big, with very little rewriting going on. I know for what I'm working on, I've decided to make at least a few choices now on the side of scaling, but I'm not going to do a complete change of thinking to get it to scale completely. Notably, I've redesigned my database from a conventional relational design to one similar to what was suggested on the Reddit site linked below, and I'm going to give memcache a try. So, the basic question, when is a good time to start thinking or worrying about scaling, and what are some good designs, tips, etc. for when doing so? A couple of things I've been reading, for those who are interested: http://www.codinghorror.com/blog/2009/06/scaling-up-vs-scaling-out-hidden-costs.html http://highscalability.com/blog/2010/5/17/7-lessons-learned-while-building-reddit-to-270-million-page.html http://developer.yahoo.com/performance/rules.html

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• wpf 4 datagrid not highlighting row.

  - by SteveCav

  I have a shiny new wpf 4 datagrid, and no matter what I do I can't make the row highlight when the user clicks on a cell. It works on the empty "new record" row on the bottom, but not on rows with data (yes I've tried with and without readonly). My XAML is: <DataGrid AutoGenerateColumns="False" Background="Beige" Height="353" SelectionUnit="FullRow" SelectionMode="Single" AlternatingRowBackground="lightcyan" HorizontalAlignment="Left" Name="dgJobs" VerticalAlignment="Top" Width="1160"> <DataGrid.Columns> <DataGridTextColumn Header="Job ID" Width="80" Binding="{Binding JobID}" IsReadOnly="True"></DataGridTextColumn> <DataGridTextColumn Header="Site" Width="SizeToCells" Binding="{Binding AssetName}" IsReadOnly="True"></DataGridTextColumn> <DataGridTextColumn Header="Category" Width="SizeToCells" Binding="{Binding CategoryName}" IsReadOnly="True"></DataGridTextColumn> <DataGridTextColumn Header="Status" Width="SizeToCells" Binding="{Binding JobStatusDesc}" IsReadOnly="True"></DataGridTextColumn> <DataGridTextColumn Header="Reason" Width="SizeToCells" Binding="{Binding Reason}" IsReadOnly="True"></DataGridTextColumn> </DataGrid.Columns> </DataGrid> Nothing too fancy, it's quite plain really. I had themes enabled because I'm using a Fluent Ribbon elsewhere and it forces you to, but I tried turning that off and it had no effect. I have a 3.5 form in another app which is also very plain and you can highlight the row on it. Why on earth isn't this one working?

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• Dynamically adding controls from an Event after Page_Init

  - by GenericTypeTea

  Might seem like a daft title as you shouldn't add dynamic controls after Page_Init if you want to maintain ViewState, but I couldn't think of a better way of explaining the problem. I have a class similar to the following: public class WebCustomForm : WebControl, IScriptControl { internal CustomRender Content { get { object content = this.Page.Session[this.SESSION_CONTENT_TRACKER]; return content as CustomRender; } private set { this.Page.Session[this.SESSION_CONTENT_TRACKER] = value; } } } CustomRender is an abstract class that implements ITemplate that I use to self-contain a CustomForms module I'm in the middle of writing. On the Page_Init of the page that holds the WebCustomForm, I Initialise the control by passing the relevant Ids to it. Then on the overridden OnInit method of the WebCustomForm I call the Instantiate the CustomRender control that's currently active: if (this.Content != null) { this.Content.InstantiateIn(this); } The problem is that my CustomRender controls need the ability to change the CustomRender control of the WebCustomForm. But when the events that fire on the CustomRender fire, the Page_Init event has obviously already gone off. So, my question is, how can I change the content of the WebCustomForm from a dynamically added control within it? The way I see it, I have two options: I separate the CustomRender controls out into their own stand alone control and basically have an aspx page per control and handle the events myself on the page (although I was hoping to just make a control I drop on the page and forget about) I don't use events and just keep requesting the current page, but with different Request Parameters Or I go back to the drawing board with any better suggetions anyone can give me.

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• How can I change Rails view code for site visitors using SSL?

  - by pjmorse

  My Rails app has some pages which are SSL-required and others which are SSL-optional. The optional pages use some assets which are served off-site (images from a vendor) which have both http and https URLs. I need to use https when the page is accessed via SSL to avoid the dreaded "this page contains both secure and insecure elements" warning. I've written code to return the image URLs as http by default and https if requested. My problem now is determining in the view how the request came in. request.ssl? doesn't work in views. I've tried using a before_filter which sets something like @ssl_request using request.ssl?, but that also always returns false. Is there a more elegant way to do this? The server stack is Nginx and Passenger. Other apps with Apache = Mongrel stacks pass an X_FORWARDED_PROTO header to tell Rails that SSL is or isn't being used; is it possible that Nginx/Passenger doesn't do this?

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• php funciton problem

  - by Holian

  Hello, i have this little script, which should ping the IPs in the host_to_ping array. This php is called with JS in the index.html. But somethin' wrong, 'coz the $rval is always 1 (which mean the host is unreachable). But i know that the first two host is alive. So i print the $res variable, and i see the message: Need to give the IP. I dont understand why dont replace the $host variable to the actual IP address in the function. <?php function ping($host) { exec(sprintf('ping -n 4', escapeshellarg($host)), $res, $rval); print_r($res); return $rval === 0; } $hosts_to_ping = array('10.54.23.254', '10.22.23.254', '10.23.66.134'); ?> <ul> <?php foreach ($hosts_to_ping as $host): ?> <li> <?php echo $host; ?> <?php $up = ping($host); ?> (<img src="<?php echo $up ? 'on' : 'off'; ?>" alt="<?php echo $up ? 'up' : 'down'; ?>">) </li> <?php endforeach; ?> </ul>

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• Transitioning from desktop app written in C++ to a web-based app

  - by Karim

  We have a mature Windows desktop application written in C++. The application's GUI sits on top of a windows DLL that does most of the work for the GUI (it's kind of the engine). It, too, is written in C++. We are considering transitioning the Windows app to be a web-based app for various reasons. What I would like to avoid is having to writing the CGI for this web-based app in C++. That is, I would rather have the power of a 4G language like Python or a .NET language for creating the web-based version of this app. So, the question is: given that I need to use a C++ DLL on the backend to do the work of the app what technology stack would you recommend for sitting between the user's browser and are C++ dll? We can assume that the web server will be Windows. Some options: Write a COM layer on top of the windows DLL which can then be access via .NET and use ASP.NET for the UI Access the export DLL interface directly from .NET and use ASP.NET for the UI. Write a custom Python library that wraps the windows DLL so that the rest of the code can be written. Write the CGI using C++ and a C++-based MVC framework like Wt Concerns: I would rather not use C++ for the web framework if it can be avoided - I think languages like Python and C# are simply more powerful and efficient in terms of development time. I'm concerned that my mixing managed and unmanaged code with one of the .NET solutions I'm asking for lots of little problems that are hard to debug (purely anecdotal evidence for that) Same is true for using a Python layer. Anything that's slightly off the beaten path like that worries me in that I don't have much evidence one way or the other if this is a viable long term solution.

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• Adding jQuery event handler to expand div when a link is clicked

  - by hollyb

  I'm using a bit of jQuery to expand/hide some divs. I need to add an event handler so that when a link is clicked, it opens a corrisponding div. Each toggled div will have a unique class assigned to it. I am looking for some advice about how to build the event handler. The jQuery $(document).ready(function(){ $(".toggle_container:not(:first)").hide(); $(".toggle_container:first").show(); $("h6.trigger:first").addClass("active"); $("h6.trigger").click(function(){ $(this).toggleClass("active"); $(this).next(".toggle_container").slideToggle(300); }); The css: // uses a background image with an on (+) and off (-) state stacked on top of each other h6.trigger { background: url(buttonBG.gif) no-repeat;height: 46px;line-height: 46px;width: 300px;font-size: 2em;font-weight: normal;} h6.trigger a {color: #fff;text-decoration: none; display: block;} h6.active {background-position: left bottom;} .toggle_container { overflow: hidden; } .toggle_container .block {padding: 20px;} The html has a list of links, such as: <a href="#">One</a> <a href="#">Two</a> and the coorisponding divs to open: <h6 class="trigger">Container one</h6> <div class="toggle_container"> div one </div> <h6 class="trigger">Container two</h6> <div class="toggle_container Open"> div one </div> As I mentioned, I will be assigning a unique class to facilitate this. Any advice? Thanks! To clarify, i'm looking for some advice to build an event handler to toggle open a specific div when a link is clicked from a different part of the page, from a nav for instance.

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• Set scaleX property on a Sprite without altering the child inside

  - by grammar

  Is this possible? My site is set up with next and prev buttons on the right and left sides respectively, and as you roll over either of the hit areas around the buttons a Sprite fades in which contains a TextField that describes the next page. Said Sprite calls the StartDrag() method, so it follows the mouse within the bounds, which is all fine and dandy on the left side of the page. Adobe, however, seems to have forgotten to put a way to dynamically alter the registration point of a Sprite, MC, whatever else, so when you roll over the right side of the page, the sprite is displayed from the top left and is mostly off the stage. Trying to hack this problem I have tried numerous things ( classes written by others, other hacks) and the best that I have found is to use the scaleX method on the Sprite, changing the scale to -1. This, of course, makes the Sprite seem like it's reflected from its normal point, which means all its children show up backwards. Is there anyway I can use this hack without it altering the text? OR Does anyone know a different way to go about displaying a Sprite from another corner? Any way to make a Sprite fade in and follow the mouse on the LEFT HAND side of the mouse pointer? Thank you very much in advance. Here is a snippet to give an idea of what's happening: naxtPage.labelBG.scaleX = -1; nextPage.labelBG.startDrag( true, nextHitRect ); nextPage.labelBG.x = nextPage.labelBG.parent.mouseX; nextPage.labelBG.y = nextPage.labelBG.parent.mouseY; Cheers

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• Discussion on SEO best-practices for site development involving php...

  - by Bradley Herman

  Recently in our work, I've started getting some experience with SEO (finally). It's something I've put off for a long time because I've always maintained that SEO is a buzz-word b.s. pseudo-science and more about providing quality, relevant content (assuming proper header tags and the basics are covered). However, sometimes a client doesn't have stellar content yet still demands SEO and high rankings. While it's not how I design sites 100% of the time (as design dictates structure), I typically create a basic template from the design my boss gives me, then I optimize it, and then strip the top and bottom and move those to header.php and footer.php, using the following to bring in the header and footer based on AJAX versus HTML requests: <?php if($_SERVER['HTTP_X_REQUESTED_WITH']==''){ include('includes/header.php'); }?> #content here <?php if($_SERVER['HTTP_X_REQUESTED_WITH']==''){ include('includes/footer.php'); }?> Then, I use jQuery to intercept page requests and I use AJAX to fill in, for example, a #copy div with the new content. This avoids unnecessarily loading all the header and footer info everytime, but still allows users without Java to access pages without any problems. (also to think about, depending on size of content, do the extra http requests added using this method render it more of a server strain versus a single, larger file?) I don't have a really solid understanding of the meta keywords and their SEO significance, but as I recall reading, the keywords, title, and description on a page should match up to the pages content--ie. each page should have slightly different keywords/description while retaining some common ground. What I'm getting at here is trying to foster a discussion on whether my approach is flawed to begin with, if there are things I can do (within reason) that keep the site structure simple but allow for better SEO practices, or if my SEO understandings are wrong. This isn't a question, per say, but hopefully a constructive discussion here that more than just I can learn from. I appreciate any responses and hope to hear from you. Thanks!

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• UITableView UITableViewCell dynamic UILabel Height storyboard

  - by Mikel Nelson

  This isn'an a question, just a results log on an issue I had with XCode 4.5 storyboards and dynamic height UITableCell with a UILabel. The issue was; the initial display of a cell would only show part of the resized UILabel contents, and that the visual UILabel was not resized. It would only display correctly after scrolling off the top of the Table and back down. I did the calculations in hieghtForRowAtIndexPath and sizeToFit the UILabel in rowAtIndexPath. The sizes where coming up ok in debug, but the device was not updating the display with the correct size and UILable.text value. I had created the dynamic UITableCell in a storyboard. However, I had set the width and height to a nominal value (290x44). It turns out, this was causing my issues. I set the width and height to zero (0) in the story board, and everything started working correctly. (i.e. the UILabels displayed at the correct size with full content). I was unable to find anything online on this issue, except for some references to creating the custom table cell with a frame of zero. Turns out, that was really the answer (for me).

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• Starting with NHibernate

  - by George

  I'm having major difficulties to start off with NHiberante. Main problems: Where my hbm.xml files should reside? I create a Mappings folder but I received an error "Could not find xxx.hbm.xml file." I tried to load the specific class through the dialect cf.AddClass(typeof(xxx)); but it still gives me the same error (the files are marked as embebed resources. Also I'm having major problems in connection to it. I stopped trying to use the cfg xml file and tried a more direct approach with a library I have here. Configuration cfg = new Configuration(); cfg.AddClass(typeof(Tag)); ISessionFactory sessions = cfg.BuildSessionFactory(); AgnosticConnectionHandler agch = new AgnosticConnectionHandler("xxx","xxx","geo_biblio","localhost", 5432,DatabaseInstance.PostgreSQL); ISession sessao = sessions.OpenSession(agch.GetConnection); ITransaction tx = sessao.BeginTransaction(); Tag tag1 = new Tag(); tag1.NomeTag = "Teste Tag NHibernate!!!"; sessao.Save(tag1); tx.Commit(); sessao.Close(); Any tips for me? I'm getting the exception in line 2 of this code, and still not sure what to do. Any help is appreciated. Thanks

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• Can LINQ expression classes implement the observer pattern instead of deferred execution?

  - by Tormod

  Hi. We have issues within an application using a state machine. The application is implemented as a windows service and is iteration based (it "foreaches" itself through everything) and there are myriads of instances being processed by the state machine. As I'm reading the MEAP version of Jon Skeets book "C# in Depth, 2nd ed", I'm wondering if I can change the whole thing to use linq expression instances so that guards and conditions are represented using expression trees. We are building many applications on this state machine engine and would probably greatly benefit from the new Expression tree visualizer in VS 2010 Now, simple example. If I have an expression tree where there is an OR Expression condition with two sub nodes, is there any way that these can implement the observer pattern so that the expression tree becomes event driven? If a condition change, it should notify its parent node (the OR node). Since the OR node then changes from "false" to "true", then it should notify ITS parent and so on. I love the declarative model of expression trees, but the deferred execution model works in opposite direction of the control flow if you want event based "live" conditions. Am I off on a wild goose chase here? Or is there some concept in the BCL that may help me achieve this?

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• DataReader already open when using LINQ

  - by Jamie Dixon

  I've got a static class containing a static field which makes reference to a wrapper object of a DataContext. The DataContext is basically generated by Visual Studio when we created a dbml file & contains methods for each of the stored procedures we have in the DB. Our class basically has a bunch of static methods that fire off each of these stored proc methods & then returns an array based on a LINQ query. Example: public static TwoFieldBarData[] GetAgesReportData(string pct) { return DataContext .BreakdownOfUsersByAge(Constants.USER_MEDICAL_PROFILE_KEY, pct) .Select(x => new TwoFieldBarData(x.DisplayName, x.LeftValue, x.RightValue, x.TotalCount)) .ToArray(); } Every now and then, we get the following error: There is already an open DataReader associated with this Command which must be closed firs This is happening intermittently and I'm curious as to what is going on. My guess is that when there's some lag between one method executing and the next one firing, it's locking up the DataContext and throwing the error. Could this be a case for wrapping each of the DataContext LINQ calls in a lock(){} to obtain exclusivity to that type and ensure other requests are queued?

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• Opa app does not load in Internet Explorer when compiled with Opa 1.1.1

  - by Marcin Skórzewski

  I did a minor update to the already working application and then had problems using new version of Opa compiler. First problem - runtime exception Since the original deployment Opa 1.1.1 has been released and it resulted in error: events.js:72 throw er; // Unhandled 'error' event ^ Error: listen EADDRINUSE at errnoException (net.js:901:11) at Server._listen2 (net.js:1039:14) at listen (net.js:1061:10) at Server.listen (net.js:1127:5) at global.BslNet_Http_server_init_server (/opt/mlstate/lib/opa/stdlib/server.opp/serverNodeJsPackage.js:223:1405) at global.BslNet_Http_server_init_server_cps (/opt/mlstate/lib/opa/stdlib/server.opp/serverNodeJsPackage.js:226:15) at __v1_bslnet_http_server_init_server_cps_b970f080 (/opt/mlstate/lib/opa/stdlib/stdlib.qmljs/stdlib.core.web.server.opx/main.js:1:175) at /opt/mlstate/lib/opa/stdlib/stdlib.qmljs/stdlib.core.web.server.opx/main.js:440:106 at global.execute_ (/opt/mlstate/lib/opa/static/opa-js-runtime-cps/main.js:19:49) at /opt/mlstate/lib/opa/static/opa-js-runtime-cps/main.js:17:78 I decided to build Opa from sources and it helped, but another problem occurred :( Second problem - stops to support the IE Application stopped to work in Internet Explorer. I tried two different machines (Windows XP and 7) with IE 8 and 10. Web page does not load at all (looks like the network problem, but the same URL works fine in Firefox). I confirmed the same problem with "Hello world" from the Opa tutorial compiled with both Opa stable 1.1.1 and build from sources. I suspected that the problem is due to Node.js update (Opa = 1.1.1 requires Node 0.10.* - now I am using 0.10.12, but I also tried other 0.10-s), but "Hello world" from the Node's from page works fine. I am running the app on OSX developer box and Linux Debian 7.0 server. Any suggestions what am I doing wrong? PS. I was off the business for a while. Anyone knows what happened to the Opa forum? Signing is seams not to work.

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• Are functional programming languages good for practical tasks?

  - by Clueless

  It seems to me from my experimenting with Haskell, Erlang and Scheme that functional programming languages are a fantastic way to answer scientific questions. For example, taking a small set of data and performing some extensive analysis on it to return a significant answer. It's great for working through some tough Project Euler questions or trying out the Google Code Jam in an original way. At the same time it seems that by their very nature, they are more suited to finding analytical solutions than actually performing practical tasks. I noticed this most strongly in Haskell, where everything is evaluated lazily and your whole program boils down to one giant analytical solution for some given data that you either hard-code into the program or tack on messily through Haskell's limited IO capabilities. Basically, the tasks I would call 'practical' such as Aceept a request, find and process requested data, and return it formatted as needed seem to translate much more directly into procedural languages. The most luck I have had finding a functional language that works like this is Factor, which I would liken to a reverse-polish-notation version of Python. So I am just curious whether I have missed something in these languages or I am just way off the ball in how I ask this question. Does anyone have examples of functional languages that are great at performing practical tasks or practical tasks that are best performed by functional languages?

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• Raising events and object persistence in Django

  - by Mridang Agarwalla

  Hi, I have a tricky Django problem which didn't occur to me when I was developing it. My Django application allows a user to sign up and store his login credentials for a sites. The Django application basically allows the user to search this other site (by scraping content off it) and returns the result to the user. For each query, it does a couple of queries of the other site. This seemed to work fine but sometimes, the other site slaps me with a CAPTCHA. I've written the code to get the CAPTCHA image and I need to return this to the user so he can type it in but I don't know how. My search request (the query, the username and the password) in my Django application gets passed to a view which in turn calls the backend that does the scraping/search. When a CAPTCHA is detected, I'd like to raise a client side event or something on those lines and display the CAPTCHA to the user and wait for the user's input so that I can resume my search. I would somehow need to persist my backend object between calls. I've tried pickling it but it doesn't work because I get the Can't pickle 'lock' object error. I don't know to implement this though. Any help/ideas? Thanks a ton.

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