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• Structuring the UI code of a single-page EXTjs Web app using Rails?

  - by Daniel Beardsley

  I’m in the process of creating a large single-page web-app using ext-js for the UI components with Rails on the backend. I’ve come to good solutions for transferring data using Whorm gem and Rails support of RESTful Resources. What I haven’t come to a conclusion on is how to structure the UI and business logic aspects of the application. I’ve had a look at a few options, including Netzke but haven’t seen anything that I really think fits my needs. How should a web-application that uses ext-js components, layouts, and controls in the browser and Rails on the server best implement UI component re-use, good organization, and maintainability while maintaining a flexible layout design. Specifically I’m looking for best-practice suggestions for structuring the code that creates and configures UI components (many UI config options will be based on user data) Should EXT classes be extended in static JS for often re-used customizations and then instantiated with various configuration options by generated JS within html partials? Should partials create javascript blocks that instantiate EXT components? Should partials call helpers that return ruby hashes for EXT component config which is then dumped to Json? Something else entirely? There are many options and I'd love to hear from people who've been down this road and found some methodology that worked for them.

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• Using the <h2> as the title after sent?

  - by Delan Azabani

  Currently, I have a semi-dynamic system for my website's pages. head.php has all the tags before the content body, foot.php the tags after. Any page using the main theme will include head.php, then write the content, then output foot.php. Currently, to be able to set the title, I quickly set a variable $title before inclusion: <?php $title = 'Untitled document'; include_once '../head.php'; ?> <h2>Untitled document</h2> Content here... <?php include_once '../foot.php'; ?> So that in head.php... <title><?php echo $title; ?> | Delan Azabani</title> However, this seems kludgy as the title is most of the time, the same as the content of the h2 tag. Is there a way I can get PHP to read the content of h2, track back and insert it, then send the whole thing at the end?

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• Doctrine - get the offset of an object in a collection (implementing an infinite scroll)

  - by dan

  I am using Doctrine and trying to implement an infinite scroll on a collection of notes displayed on the user's browser. The application is very dynamic, therefore when the user submits a new note, the note is added to the top of the collection straightaway, besides being sent (and stored) to the server. Which is why I can't use a traditional pagination method, where you just send the page number to the server and the server will figure out the offset and the number of results from that. To give you an example of what I mean, imagine there are 20 notes displayed, then the user adds 2 more notes, therefore there are 22 notes displayed. If I simply requests "page 2", the first 2 items of that page will be the last two items of the page currently displayed to the user. Which is why I am after a more sophisticated method, which is the one I am about to explain. Please consider the following code, which is part of the server code serving an AJAX request for more notes: // $lastNoteDisplayedId is coming from the AJAX request $lastNoteDisplayed = $repository->findBy($lastNoteDisplayedId); $allNotes = $repository->findBy($filter, array('createdAt' => 'desc')); $offset = getLastNoteDisplayedOffset($allNotes, $lastNoteDisplayedId); // retrieve the page to send back so that it can be appended to the listing $notesPerPage = 30 $notes = $repository->findBy( array(), array('createdAt' => 'desc'), $notesPerPage, $offset ); $response = json_encode($notes); return $response; Basically I would need to write the method getLastNoteDisplayedOffset, that given the whole set of notes and one particoular note, it can give me its offset, so that I can use it for the pagination of the previous Doctrine statement. I know probably a possible implementation would be: getLastNoteDisplayedOffset($allNotes, $lastNoteDisplayedId) { $i = 0; foreach ($allNotes as $note) { if ($note->getId() === $lastNoteDisplayedId->getId()) { break; } $i++; } return $i; } I would prefer not to loop through all notes because performance is an important factor. I was wondering if Doctrine has got a method itself or if you can suggest a different approach.

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• ScriptManager duplicates javascript

  - by Andreas

  Hi! I have a usercontrol that can be used in for example a gridview itemtemplate, this means that the control might or might not be on the page at page load. In the case where the control is inside an itemtemplate i will popupate the gridview via asyncronous postbacks (via updatepanels). The control itselfs registrers scriptblocks since it is depending on javascripts. First i used Page.ClientScript.RegistrerClientScriptBlock But this doesn't work on asyncronous postbacks (updatepanels) so i then tried the same using ScriptManager which allows me to registrer scripts on the page after async postbacks. great!. ScriptManager.RegisterClientScriptBlock However, ScriptManager (what i know of) does not have the functionallity to see if a script already is on the page, so i will for every postback generate duplicates of the script blocks, this is ofcourse unwanted behaviour. I did a run at Google and found that i can call the Dispose() method of the PageRequestManager can be used, this does work since it clears the scripts and then adding them again (this also solves my issue with removing unused script blocks from removed controls). Sys.WebForms.PageRequestManager.getInstance().Dispose() However, ofcourse there is a downside since im posting here :). The Dispose() method disposes the instance on the master page as well which leads to scripts running there will stop to function after an async postback (updateprogress for example). So, is there a way to check if a script already exists on the page using ScriptManager or any other tools, that will prevent me of inserting duplicate scripts? Also, is there a way to remove certain script blocks (when i am removing an item in itemtemplate for example). Big thanks in advance.

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• How to get at specific HTML elements of a document using C# and Hide them/Show them etc.

  - by LaserBeak

  Basically I want to load a HTML document and using controls such as multiple check boxes which will be programmed to hide, delete or show HTML elements with certain ID's. So I am thinking I would have to set an inline CSS property for visibility to: false on the ones I want to hide or delete them altogether when necessary. I need this so I don't have to edit my Ebay HTML templates in dreamweaver all the time, where I usually have to scroll around messy code and manually delete or add tags and their respective content. Whereas I just want to create one master template in dreamweaver which has all the variations that my products have, since they are all of the same genre with slight changes here and there and I just need to enable and disable the visibility of these variants as required and copy + paste the final html. I haven's used Windows Forms before, but tried doing this in WebForms which I do know a bit. I am able to get the result that I want by wrapping any HTML elements in a <asp:PlaceHolder></asp:PlaceHolder> and just setting that place holders visibility to false after the associated checkbox is checked and a postback occurs, finally I add a checkbox/button control that removes all the checkboxes, including itself etc for final html. But this method seems just like too much pain in the ass as I have to add the placeholder tags around everything that I need control over as ordinary html elements do not run at server, also webforms injects a bunch of Javascript and ViewState data so I don't have clean HTML which I can just copy after viewing the page source. Any tips/code that you can suggest to achieve the desired effect with the least changes required to existing HTML documents? Ideally I would want to load the HTML document in, have a live design preview of it and underneath have a bunch of well labelled checkboxes programmed to hide, delete or show elements with certain ID's. Thanks...

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• Java abstract visitor - guarantueed to succeed? If so, why?

  - by disown

  I was dealing with hibernate, trying to figure out the run-time class behind proxied instances by using the visitor pattern. I then came up with an AbstractVisitable approach, but I wonder if it will always produce correct results. Consider the following code: interface Visitable { public void accept(Visitor v); } interface Visitor { public void visit(Visitable visitorHost); } abstract class AbstractVisitable implements Visitable { @Override public void accept(Visitor v) { v.visit(this); } } class ConcreteVisitable extends AbstractVisitable { public static void main(String[] args) { final Visitable visitable = new ConcreteVisitable(); final Visitable proxyVisitable = (Visitable) Proxy.newProxyInstance( Thread.currentThread().getContextClassLoader(), new Class<?>[] { Visitable.class }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return method.invoke(visitable, args); } }); proxyVisitable.accept(new Visitor() { @Override public void visit(Visitable visitorHost) { System.out.println(visitorHost.getClass()); } }); } } This makes a ConcreteVisitable which inherits the accept method from AbstractVisitable. In c++, I would consider this risky, since this in AbstractVisitable could be referencing to AbstractVisitable::this, and not ConcreteVisitable::this. I was worried that the code under certain circumstances would print class AbstractVisible. Yet the code above outputs class ConcreteVisitable, even though I hid the real type behind a dynamic proxy (the most difficult case I could come up with). Is the abstract visitor approach above guaranteed to work, or are there some pitfalls with this approach? What guarantees are given in Java with respect to the this pointer?

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• css Checkbox Label Selector

  - by HW90

  I'm developing a MVC3 application and need to select the checkboxes label. In ASP MVC3 you have helper methods which creat a part of the code. So the code for a checkbox looks like this: <input id="Jumping_successleicht" type="checkbox" value="true" name="Jumping_successleicht"> <input type="hidden" value="false" name="Jumping_successleicht"> <label for="Jumping_successleicht"> <span>leicht (4)</span> </label> Now I've thought I can use following code to select the label: input[type=checkbox] + label { background: url("../../Images/Controls/Checkbox.png") no-repeat scroll left center transparent; clear: none; cursor: pointer; margin: 0; padding: 5px 0 4px 24px; } But it does not work. It looks like label and input have to be next to each other. Does any ony have a solution how to solve this problem?

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• Performance of C# method polymorphism with generics

  - by zildjohn01

  I noticed in C#, unlike C++, you can combine virtual and generic methods. For example: using System.Diagnostics; class Base { public virtual void Concrete() {Debug.WriteLine("base concrete");} public virtual void Generic<T>() {Debug.WriteLine("base generic");} } class Derived : Base { public override void Concrete() {Debug.WriteLine("derived concrete");} public override void Generic<T>() {Debug.WriteLine("derived generic");} } class App { static void Main() { Base x = new Derived(); x.Concrete(); x.Generic<PerformanceCounter>(); } } Given that any number of versions of Generic<T> could be instantiated, it doesn't look like the standard vtbl approach could be used to resolve method calls, and in fact it's not. Here's the generated code: x.Concrete(); mov ecx,dword ptr [ebp-8] mov eax,dword ptr [ecx] call dword ptr [eax+38h] x.Generic<PerformanceCounter>(); push 989A38h mov ecx,dword ptr [ebp-8] mov edx,989914h call 76A874F1 mov dword ptr [ebp-4],eax mov ecx,dword ptr [ebp-8] call dword ptr [ebp-4] The extra code appears to be looking up a dynamic vtbl according to the generic parameters, and then calling into it. Has anyone written about the specifics of this implementation? How well does it perform compared to the non-generic case?

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• Google Maps: Simple app not working on IE

  - by Peter Bridger

  We have a simple Google Maps traffic application up at: http://www.avonandsomerset.police.uk/newsroom/traffic/ For some reason it's recently stopped working in IE correctly. At this point in time it was using V2 of the API, so I've just upgraded it to use V3 - but it still won't work in IE. It works fine in Chrome & Firefox. But in all versions of IE I've tired (6,7,8) the Google Map doesn't load fully. The problem The Google Map DIV will generally load all the controls (Zoom, Powered by Google, map types) but the actual map tiles do not appear in IE. I can just see the grey background of the DIV What I've tried I've commented down the JavaScript code to just the following on the page, but it still has the same problem: <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script> <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script> <script type="text/javascript" > var map; $(document).ready(function () { initialize(); // Set-up Google map }); function initialize() { var options = { zoom: 9, center: new google.maps.LatLng(51.335759, -2.870178), mapTypeId: google.maps.MapTypeId.ROADMAP }; map = new google.maps.Map(document.getElementById("googleMap"), options); } </script>

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• InvalidOperationException: The Undo operation encountered a context that is different from what was

  - by McN

  I got the following exception: Exception Type: System.InvalidOperationException Exception Message: The Undo operation encountered a context that is different from what was applied in the corresponding Set operation. The possible cause is that a context was Set on the thread and not reverted(undone). Exception Stack: at System.Threading.SynchronizationContextSwitcher.Undo() at System.Threading.ExecutionContextSwitcher.Undo() at System.Threading.ExecutionContext.runFinallyCode(Object userData, Boolean exceptionThrown) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteBackoutCodeHelper(Object backoutCode, Object userData, Boolean exceptionThrown) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Net.ContextAwareResult.Complete(IntPtr userToken) at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken) at System.Net.Sockets.BaseOverlappedAsyncResult.CompletionPortCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped) at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP) Exception Source: mscorlib Exception TargetSite.Name: Undo Exception HelpLink: The application is a Visual Studio 2005 (.Net 2.0) console application. It is a server for multiple TCP/IP connections, doing asynchronous socket reads and synchronous socket writes. In searching for an answer I came across this post which talks about a call to Application.Doevents() which I don't use in my code. I also found this post which has a resolution involved with Component which I also don't use in my code. The application does reference a library that I created that contains custom user controls and components, but they are not being used by the application. Question: What caused this to happen and how do I prevent this from happening again? Or a more realistic question: What does this exception actually mean? How is "context" defined in this situation? Anything that can help me understand what is going on would be very much appreciated.

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• cell and array in Matlab

  - by Tim

  Hi, I am a little confused about the usage of cell and array in Matlab. I would like to hear about your understandings. Here are my observations: (1). array can dynamically adjust its own memory to allow dynamic number of elements, while cell seems not act in the same way. a=[]; a=[a 1]; b={}; b={b 1}; (2). several elements can be retrieved from cell, while they seem not from array. a={'1' '2'}; figure, plot(...); hold on; plot(...) ; legend(a{1:2}); b=['1' '2']; figure, plot(...); hold on; plot(...) ; legend(b(1:2)); % b(1:2) is an array, not its elements, so it is wrong with legend. Are these correct? What are some other different usages between the cell and array? Thanks and regards!

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• What's a good way to provide additional decoration/metadata for Python function parameters?

  - by Will Dean

  We're considering using Python (IronPython, but I don't think that's relevant) to provide a sort of 'macro' support for another application, which controls a piece of equipment. We'd like to write fairly simple functions in Python, which take a few arguments - these would be things like times and temperatures and positions. Different functions would take different arguments, and the main application would contain user interface (something like a property grid) which allows the users to provide values for the Python function arguments. So, for example function1 might take a time and a temperature, and function2 might take a position and a couple of times. We'd like to be able to dynamically build the user interface from the Python code. Things which are easy to do are to find a list of functions in a module, and (using inspect.getargspec) to get a list of arguments to each function. However, just a list of argument names is not really enough - ideally we'd like to be able to include some more information about each argument - for instance, it's 'type' (high-level type - time, temperature, etc, not language-level type), and perhaps a 'friendly name' or description. So, the question is, what are good 'pythonic' ways of adding this sort of information to a function. The two possibilities I have thought of are: Use a strict naming convention for arguments, and then infer stuff about them from their names (fetched using getargspec) Invent our own docstring meta-language (could be little more than CSV) and use the docstring for our metadata. Because Python seems pretty popular for building scripting into large apps, I imagine this is a solved problem with some common conventions, but I haven't been able to find them.

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• Windows Phone 8 Panorama SelectionIndex not changing on swiping through items

  - by Balraj Singh

  I have created Panorama control and binded PanoramaItem from ItemSource. Now when i am changing the selected Panoramaitem by swiping over them the Selected index is always set to -1. I dont know what wrong i am doing while implementation. neither selectionchange event is getting fired. Code: <phone:Panorama Grid.Row="1" Visibility="Visible" x:Name="PnrVwMainNews" ItemsSource="{Binding ParnormaItemsData}" ItemContainerStyle="{StaticResource PanoramaContainerItemStyle}"> <phone:Panorama.ItemTemplate> <DataTemplate> <!-- Panorma Items Template --> <Controls:DynamicContentControl Content="{Binding UsrCntrlDynamic}" /> </DataTemplate> </phone:Panorama.ItemTemplate> </phone:Panorama> PanoramaContainerItemStyle <Style x:Key="PanoramaContainerItemStyle" TargetType="phone:PanoramaItem"> <Setter Property="HorizontalContentAlignment" Value="Stretch" /> <Setter Property="VerticalContentAlignment" Value="Stretch" /> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="phone:PanoramaItem"> <Grid Background="{TemplateBinding Background}" Margin="12,0,0,0"> <Grid.RowDefinitions> <RowDefinition Height="auto" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <ContentPresenter Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" Grid.Row="1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" /> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style>

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• Type classe, generic memoization

  - by nicolas

  Something quite odd is happening with y types and I quite dont understand if this is justified or not. I would tend to think not. This code works fine : type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, obj>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res And this ones complains type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, _>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res The difference is only the underscore in the dictionary definition. The infered types are the same, but the dynamic cast from r to type 'b exhibits an error. 'this runtime coercition ... runtime type tests are not allowed on some types, etc..' Am I missing something or is it a rough edge ?

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• ASP.NET web form Routing issue via UNC Path

  - by Slash

  I create a IIS 7.0 website via UNC path to load .aspx to dynamic compile files and runs. however, it's running perfect. I always use IIS URL Rewrite module 2 to rewrite my site URL n' its perfect, too. Today, I wanna use System.Web.Routing to implement url rewrite but I encountered difficulties... When I wrote code in Global.asax: System.Web.Routing.RouteTable.Routes.MapPageRoute("TEST", "AAA/{prop}", "~/BBB/CCC.aspx"); And it just CANNOT reDirect to /BBB/CCC.aspx When I type the URL(like: xx.xx.xx.xx/BBB/CCC.aspx) in browser directly, it runs normally that I want. (so it proof CCC.aspx is in right path.) thus, I copy all of the code and open VS2010 running with IIS 7.5 Express locally, it works perfect! e.g: in browser URL I type xx.xx.xx.xx/AAA/1234, it will turn to page xx.xx.xx.xx/BBB/CCC.aspx (Works perfect!) Why??? help me plz. thanks. Update: I think I should consider not UNC path to make it error! when I move all code to physical disk and setup IIS 7.0 to monitor this Folder, it still not works! But the same code run in VS2010 + IIS 7.5 Express it works!? so strange!

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• Algorithm Question

  - by Ravi

  Hi, I am trying to find a O (n) algorithm for this problem but unable to do so even after spending 3 - 4 hours. The brute force method times out (O (n^2)). I am confused as to how to do it ? Does the solution requires dynamic programming solution ? http://acm.timus.ru/problem.aspx?space=1&num=1794 In short the problem is this: There are some students sitting in circle and each one of them has its own choice as to when he wants to be asked a question from a teacher. The teacher will ask the questions in clockwise order only. For example: 5 3 3 1 5 5 This means that there are 5 students and : 1st student wants to go third 2nd student wants to go third 3rd student wants to go first 4th student wants to go fifth 5th student wants to go fifth. The question is as to where should teacher start asking questions so that maximum number of students will get the turn as they want. For this particular example, the answer is 5 because 3 3 1 5 5 2 3 4 5 1 You can see that by starting at fifth student as 1st, 2 students (3 and 5) are getting the choices as they wanted. For this example the answer is 12th student : 12 5 1 2 3 6 3 8 4 10 3 12 7 because 5 1 2 3 6 3 8 4 10 3 12 7 2 3 4 5 6 7 8 9 10 11 12 1 four students get their choices fulfilled. Thanks Ravi

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• Is there a term for this concept, and does it exist in a static-typed language?

  - by Strilanc

  Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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• iPodMusicPlayer playbackState inaccurate after odd conditions

  - by Shane Costello

  I have a simple music player app that runs into a really weird problem. First of all, while playing music and in the locked state, I allow the user to double click the Home button and use the locked iPod music controls. I did notice however that while in the locked state, my app doesn't receive any of its registered notifications. For the most part, this is fine anyway. But, if the user is playing music for at least 15 minutes (I'm not sure why but any less and this problem doesn't occur) while in the locked state, and using some kind of headphone or aux jack, then unplugs the headphone/aux jack while the device is still playing music, the iPodMusicPlayer will auto-pause. Which is exactly what I would want it to do, but after this happens, when the user unlocks their device and gives focus to the app again, the iPodMusicPlayer's playbackState is inaccurate. - (IBAction)playPause:(id)sender { if ([musicPlayer playbackState] == MPMusicPlaybackStatePlaying) { [musicPlayer pause]; } else { [musicPlayer play]; } } where musicPlayer = [MPMusicPlayerController iPodMusicPlayer]. Under normal circumstances, this runs perfectly fine. But after these conditions, my breakpoint will hit the condition for MPMusicPlaybackStatePlaying while the music is paused, and vice versa. The only way I've been able to fix this is to either make a new selection of music or to terminate the app and reopen. I've tried tons of a workarounds to fix this problem programmatically, but nothing turns out a 100% bug free fix. Does anyone have any clue as to why this happens in the first place?

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• How can I clear viewstate of a dropdownlist inside a usercontrol? Should I?

  - by tbilly

  I have a web user control with a dropdownlist inside of it. When the usercontrol's databind event is called, it automatically fires the dropdownlists databind event. In the dropdownlist's ondatabound event handler an 'other' option is appended to the end of the dropdownlist. The usercontrol is loaded multiple times, depending on selection of other controls on the page. When the page loads initially, there are no items in the usercontrol except the 'other' option. Then when I call the user control's databind event the control reloads, with 4 items plus the 'other' option. The text for the first item in the list is the 'other' option's text, not what it should be. I've stepped through the databound event of the dropdownlist and have found that all items are loading correctly. It appears that the dropdownlist's viewstate is the culprit, that the dropdownlist's original item[1] text is overwriting the new text. I've tried disabling viewstate on the dropdownlist, but then it wouldn't load at all. Should I try to clear the dropdownlist's viewstate? How do I do that? Any suggestions would be greatly appreciated.

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• Why is using a common-lookup table to restrict the status of entity wrong?

  - by FreshCode

  According to Five Simple Database Design Errors You Should Avoid by Anith Sen, using a common-lookup table to store the possible statuses for an entity is a common mistake. Why is this wrong? I disagree that it's wrong, citing the example of jobs at a repair service with many possible statuses that generally have a natural flow, eg.: Booked In Assigned to Technician Diagnosing problem Waiting for Client Confirmation Repaired & Ready for Pickup Repaired & Couriered Irreparable & Ready for Pickup Quote Rejected Arguably, some of these statuses can be normalised to tables like Couriered Items, Completed Jobs and Quotes (with Pending/Accepted/Rejected statuses), but that feels like unnecessary schema complication. Another common example would be order statuses that restrict the status of an order, eg: Pending Completed Shipped Cancelled Refunded The status titles and descriptions are in one place for editing and are easy to scaffold as a drop-down with a foreign key for dynamic data applications. This has worked well for me in the past. If the business rules dictate the creation of a new order status, I can just add it to OrderStatus table, without rebuilding my code.

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• Apples, oranges, and pointers to the most derived c++ class

  - by Matthew Lowe

  Suppose I have a bunch of fruit: class Fruit { ... }; class Apple : public Fruit { ... }; class Orange: public Fruit { ... }; And some polymorphic functions that operate on said fruit: void Eat(Fruit* f, Pesticide* p) { } void Eat(Apple* f, Pesticide* p) { ingest(f,p); } void Eat(Orange* f, Pesticide* p) { peel(f,p); ingest(f,p); } OK, wait. Stop right there. Note at this point that any sane person would make Eat() a virtual member function of the Fruit classes. But that's not an option, because I am not a sane person. Also, I don't want that Pesticide* in the header file for my fruit class. Sadly, what I want to be able to do next is exactly what member functions and dynamic binding allow: typedef list<Fruit*> Fruits; Fruits fs; ... for(Fruits::iterator i=fs.begin(), e=fs.end(); i!=e; ++i) Eat(*i); And obviously, the problem here is that the pointer we pass to Eat() will be a Fruit*, not an Apple* or an Orange*, therefore nothing will get eaten and we will all be very hungry. So what I really want to be able to do instead of this: Eat(*i); is this: Eat(MAGIC_CAST_TO_MOST_DERIVED_CLASS(*i)); But to my limited knowledge, such magic does not exist, except possibly in the form of a big nasty if-statement full of calls to dynamic_cast. So is there some run-time magic of which I am not aware? Or should I implement and maintain a big nasty if-statement full of dynamic_casts? Or should I suck it up, quit thinking about how I would implement this in Ruby, and allow a little Pesticide to make its way into my fruit header?

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• Problem with NSString

  - by Kassar

  I have a problem with NSString in dynamic binding ... I manipulate with Facebook library, when i'll share my story i should make an instance of FBStreamDialog and charge its attributes with values of the story then show it, like this: FBStreamDialog* dialog = [[[FBStreamDialog alloc] init]autorelease]; dialog.delegate = self; dialog.userMessagePrompt = @"prompt"; NSString* sss=@"{ \"name\":\"%@\", \"href\":\"%@\", \"caption\":\"%@\", \"description\":\"%@\" , \"media\":[{ \"type\":\"image\", \"src\":\"%@\", \"href\":\"%@\" }] }"; dialog.attachment = [NSString stringWithFormat:sss,@"title",@"http://www.docs.com/hi.html",@"caption",@"summary",@"http://www.images.com/206.jpg",@"http://www.images.com/206.jpg"]; NSLog(@"ATTACHMENT: %@",dialog.attachment); The code above is running well. But my problem is when i want to charge these attributes dynamically like this: BStreamDialog* dialog = [[[FBStreamDialog alloc] init]autorelease]; dialog.delegate = self; dialog.userMessagePrompt = @"prompt"; NSString* sss=@"{ \"name\":\"%@\", \"href\":\"%@\", \"caption\":\"%@\", \"description\":\"%@\" , \"media\":[{ \"type\":\"image\", \"src\":\"%@\", \"href\":\"%@\" }] }"; dialog.attachment = [NSString stringWithFormat:sss,story.title,story.link,story.caption,story.summary,story.imagelink,story.imagelink]; NSLog(@"ATTACHMENT: %@",dialog.attachment); It's running without crash but it doesn't share the story it share a blank one !!! Although, it shows in the console (output of NSLog) the value of attachment is true !!! Could you plz help me. Sorry for my english.

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• Working with libpath with java reflection.

  - by C. Ross

  I'm dynamically loading a class and calling a method on it. This class does JNI. When I call the class, java attempts to load the library. This causes an error because the library is not on the libpath. I'm calling from instead a jar so I can't easily change the libpath (especially since the library is not in the same directory or a sub directory of the jar). I do know the path of the library, but how can I load it before I load the class. Current code: public Class<?> loadClass(String name) throws ClassNotFoundException { if(!CLASS_NAME.equals(name)) return super.loadClass(name); try { URL myUrl = new URL(classFileUrl); URLConnection connection = myUrl.openConnection(); InputStream input = connection.getInputStream(); byte[] classData = readConnectionToArray(input); return defineClass(CLASS_NAME, classData, 0, classData.length); } catch (MalformedURLException e) { throw new UndeclaredThrowableException(e); } catch (IOException e) { throw new UndeclaredThrowableException(e); } } Exception: Can't find library libvcommon.so java.lang.UnsatisfiedLinkError: vcommon (A file or directory in the path name does not exist.) at java.lang.ClassLoader.loadLibraryWithPath(ClassLoader.java:998) at java.lang.ClassLoader.loadLibraryWithClassLoader(ClassLoader.java:962) at java.lang.System.loadLibrary(System.java:465) at vcommon.(vcommon.java:103) at java.lang.J9VMInternals.initializeImpl(Native Method) at java.lang.J9VMInternals.initialize(J9VMInternals.java:200) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37) at java.lang.reflect.Method.invoke(Method.java:599) at com.fortune500.fin.v.vunit.reflection.ReflectionvProcessor.calculateV(ReflectionvProcessor.java:36) at com.fortune500.fin.v.vunit.UTLTestCase.execute(UTLTestCase.java:42) at com.fortune500.fin.v.vunit.TestSuite.execute(TestSuite.java:15) at com.fortune500.fin.v.vunit.batch.Testvendor.execute(Testvendor.java:101) at com.fortune500.fin.v.vunit.batch.Testvendor.main(Testvendor.java:58) Related: Dynamic loading a class in java with a different package name

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• Observer pattern and violation of Single Responsibility Principle

  - by Devil Jin

  I have an applet which repaints itself once the text has changed Design 1: //MyApplet.java public class MyApplet extends Applet implements Listener{ private DynamicText text = null; public void init(){ text = new DynamicText("Welcome"); } public void paint(Graphics g){ g.drawString(text.getText(), 50, 30); } //implement Listener update() method public void update(){ repaint(); } } //DynamicText.java public class DynamicText implements Publisher{ // implements Publisher interface methods //notify listeners whenever text changes } Isn't this a violation of Single Responsibility Principle where my Applet not only acts as Applet but also has to do Listener job. Same way DynamicText class not only generates the dynamic text but updates the registered listeners. Design 2: //MyApplet.java public class MyApplet extends Applet{ private AppletListener appLstnr = null; public void init(){ appLstnr = new AppletListener(this); // applet stuff } } // AppletListener.java public class AppletListener implements Listener{ private Applet applet = null; public AppletListener(Applet applet){ this.applet = applet; } public void update(){ this.applet.repaint(); } } // DynamicText public class DynamicText{ private TextPublisher textPblshr = null; public DynamicText(TextPublisher txtPblshr){ this.textPblshr = txtPblshr; } // call textPblshr.notifyListeners whenever text changes } public class TextPublisher implments Publisher{ // implements publisher interface methods } Q1. Is design 1 a SPR violation? Q2. Is composition a better choice here to remove SPR violation as in design 2.

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• HTML5 or Flash?

  - by lewiguez

  I have to write a web application for a client soon. Looking at the specs, there is no reason why the project couldn't be an HTML5/CSS/Javascript project, but the client is arguing that it has to be Flash. The project has a number of dynamic elements and is web-based. It'll only be used in-house by a small number of people and all of those people use either Google Chrome or Safari 4. They are all pretty tech-savvy to boot. My question is this: what are some of the reasons (preferably technical since this is Stack Overflow) I can present to my client as to why HTML5 is better than Flash (that's assuming I'm right and it is in this case)? Is it OK to use HTML5 even though it's still a draft spec (I'm assuming it is after checking out all those Apple HTML5 demos a few days ago)? Also, would a hybrid approach be preferable for now? Something that uses Flash wherever the canvas object would've been used in the HTML5 approach and that conforms to a normal XHTML approach. Help!

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