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  • ASP .NET Added Event Handlers to buttons on Page_Load. Event handlers do not fire the first click, b

    - by John
    Background: I am customizing an existing ASP .NET / C# application. It has it's own little "framework" and conventions for developers to follow when extending/customizing its functionality. I am currently extending some of it's administrative functionality, to which the framework provides a contract to enforce implementation of the GetAdministrationInterface() method, which returns System.Web.UI.Control. This method is called during the Page_Load() method of the page hosting the GUI interface. Problem: I have three buttons in my GUI, each of which have been assigned an Event Handler. My administration GUI loads up perfectly fine, but clicking any of the buttons doesn't do what I expect them to do. However, when I click them a second time, the buttons work. I placed breakpoints at the the beginning of each event handler method and stepped through my code. On the first click, none of the event handlers are triggered. On the second click, they are triggered. Any ideas? Example of Button Definition Button btn = new Button(); btn.Text = "Click Me Locked Screen"; bth.Click += new EventHandler(Btn_Click); Example of Event Handler Method Definition void Btn_Click(object sender, EventArgs e) { // Do Something }

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  • Credit Card storage solution

    - by jtnire
    Hi Everyone, I'm developing a solution that is designed to store membership details, as well as credit card details. I'm trying to comply with PCI DSS as much as I can. Here is my design so far: PAN = Primary account number == long number on credit card Server A is a remote server. It stores all membership details (Names, Address etc..) and provides indivudal Key A's for each PAN stored Server B is a local server, and actually holds the encrypted PANs, as well as Key B, and does the decryption. To get a PAN, the client has to authenticate with BOTH servers, ask Server A for the respective Key A, then give Key A to server B, which will return the PAN to the client (provided authentication was sucessful). Server A will only ever encrypt Key A with Server B's public Key, as it will have it beforehand. Server B will probably have to send a salt first though, however I doin't think that has to be encrypted I havn't really thought about any implementation (i.e. coding) specifics yet regarding the above, however the solution is using Java's Cajo framework (wrapper for RMI) so that is how the servers will communicate with each other (Currently, membership details are transfered in this way). The reason why I want Server B to do the decryption, and not the client, is that I am afraid of decryption keys going into the client's RAM, even though it's probably just as bad on the server... Can anyone see anything wrong with the above design? It doesn't matter if the above has to be changed. Thanks jtnire

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  • How to get the size of a binary tree ?

    - by Andrei Ciobanu
    I have a very simple binary tree structure, something like: struct nmbintree_s { unsigned int size; int (*cmp)(const void *e1, const void *e2); void (*destructor)(void *data); nmbintree_node *root; }; struct nmbintree_node_s { void *data; struct nmbintree_node_s *right; struct nmbintree_node_s *left; }; Sometimes i need to extract a 'tree' from another and i need to get the size to the 'extracted tree' in order to update the size of the initial 'tree' . I was thinking on two approaches: 1) Using a recursive function, something like: unsigned int nmbintree_size(struct nmbintree_node* node) { if (node==NULL) { return(0); } return( nmbintree_size(node->left) + nmbintree_size(node->right) + 1 ); } 2) A preorder / inorder / postorder traversal done in an iterative way (using stack / queue) + counting the nodes. What approach do you think is more 'memory failure proof' / performant ? Any other suggestions / tips ? NOTE: I am probably going to use this implementation in the future for small projects of mine. So I don't want to unexpectedly fail :).

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  • Comparing two Objects which implement the same interface for equality / equivalence - Design help

    - by gav
    Hi All, I have an interface and two objects implementing that interface, massively simplied; public interface MyInterface { public int getId(); public int getName(); ... } public class A implements MyInterface { ... } public class B implements MyInterface { ... } We are migrating from using one implementation to the other but I need to check that the objects of type B that are generated are equivalent to those of type A. Specifically I mean that for all of the interface methods an object of Type A and Type B will return the same value (I'm just checking my code for generating this objects is correct). How would you go about this? Map<String, MyInterface> oldGeneratedObjects = getOldGeneratedObjects(); Map<String, MyInterface> newGeneratedObjects = getNewGeneratedObjects(); // TODO: Establish that for each Key the Values in the two maps return equivalent values. I'm looking for good coding practices and style here. I appreciate that I could just iterate through one key set pulling out both objects which should be equivalent and then just call all the methods and compare, I'm just thinking there may be a cleaner, more extensible way and I'm interested to learn what options there might be. Would it be appropriate / possible / advised to override equals or implement Comparable? Thanks in advance, Gavin

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  • To OpenID or not to OpenID? Is it worth it?

    - by Eloff
    Does OpenID improve the user experience? Edit Not to detract from the other comments, but I got one really good reply below that outlined 3 advantages of OpenID in a rational bottom line kind of way. I've also heard some whisperings in other comments that you can get access to some details on the user through OpenID (name? email? what?) and that using that it might even be able to simplify the registration process by not needing to gather as much information. Things that definitely need to be gathered in a checkout process: Full name Email (I'm pretty sure I'll have to ask for these myself) Billing address Shipping address Credit card info There may be a few other things that are interesting from a marketing point of view, but I wouldn't ask the user to manually enter anything not absolutely required during the checkout process. So what's possible in this regard? /Edit (You may have noticed stackoverflow uses OpenID) It seems to me it is easier and faster for the user to simply enter a username and password in a signup form they have to go through anyway. I mean you don't avoid entering a username and password either with OpenID. But you avoid the confusion of choosing a OpenID provider, and the trip out to and back from and external site. With Microsoft making Live ID an OpenID provider (More Info), bringing on several hundred million additional accounts to those provided by Google, Yahoo, and others, this question is more important than ever. I have to require new customers to sign up during the checkout process, and it is absolutely critical that the experience be as easy and smooth as possible, every little bit harder it becomes translates into lost sales. No geek factor outweighs cold hard cash at the end of the day :) OpenID seems like a nice idea, but the implementation is of questionable value. What are the advantages of OpenID and is it really worth it in my scenario described above?

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  • What hash algorithms are paralellizable? Optimizing the hashing of large files utilizing on mult-co

    - by DanO
    I'm interested in optimizing the hashing of some large files (optimizing wall clock time). The I/O has been optimized well enough already and the I/O device (local SSD) is only tapped at about 25% of capacity, while one of the CPU cores is completely maxed-out. I have more cores available, and in the future will likely have even more cores. So far I've only been able to tap into more cores if I happen to need multiple hashes of the same file, say an MD5 AND a SHA256 at the same time. I can use the same I/O stream to feed two or more hash algorithms, and I get the faster algorithms done for free (as far as wall clock time). As I understand most hash algorithms, each new bit changes the entire result, and it is inherently challenging/impossible to do in parallel. Are any of the mainstream hash algorithms parallelizable? Are there any non-mainstream hashes that are parallelizable (and that have at least a sample implementation available)? As future CPUs will trend toward more cores and a leveling off in clock speed, is there any way to improve the performance of file hashing? (other than liquid nitrogen cooled overclocking?) or is it inherently non-parallelizable?

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  • Android How to get position of selected item from gridview without using onclicklistner, using ontouchlistner instead

    - by zonemikel
    I have a gridview, I need to do stuff on motioneven.action_down and do something for motioneven.action_up ... using onclicklistener is great but does not give me this needed functionality. Is there anyway to easily call the gridview and get its selected item in a ontouchlistener ? I've been having limited success with making my own implementation. Its hard to get the right x,y because if i call the child it gives me the x and y relative to the child so a button would be 0,0 to 48,48 but it does not tell you the actual location on the screen relative to the gridview or the screen itself. this is what i've been doing, its partially working so far. Grid.setOnTouchListener(new OnTouchListener() { public boolean onTouch(View v, MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN) { int x = (int)event.getX(); int y = (int)event.getY(); int position = 0; int childCount = Grid.getChildCount(); Message msg = new Message(); Rect ButtonRect = new Rect(); Grid.getChildAt(0).getDrawingRect(ButtonRect); int InitialLeft = ButtonRect.left + 10; ButtonRect.offsetTo(InitialLeft, ButtonRect.top); // while(position < childCount){ if(ButtonRect.contains(x,y)){break;} if(ButtonRect.right + ButtonRect.width() > Grid.getWidth()) { ButtonRect.offsetTo(InitialLeft, ButtonRect.bottom);} position++; ButtonRect.offsetTo(ButtonRect.right, ButtonRect.top); } msg.what = position; msg.arg1 = ButtonRect.bottom; msg.arg2 = y; cHandler.sendMessage(msg); }// end if action up if (event.getAction() == MotionEvent.ACTION_UP) { } return false; } });

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  • Linq2Sql: query - subquery optimisation

    - by Budda
    I have the following query: IList<InfrStadium> stadiums = (from sector in DbContext.sectors where sector.Type=typeValue select new InfrStadium(sector.TeamId) ).ToList(); and InfrStadium class constructor: private InfrStadium(int teamId) { IList<Sector> teamSectors = (from sector in DbContext.sectors where sector.TeamId==teamId select sector) .ToList<>(); ... work with data } Current implementation perform 1+n queries, where n - number of records fetched the 1st time. I want to optimize that. And another one I would love to do using 'group' operator in way like this: IList<InfrStadium> stadiums = (from sector in DbContext.sectors group sector by sector.TeamId into team_sectors select new InfrStadium(team_sectors.Key, team_sectors) ).ToList(); with appropriate constructor: private InfrStadium(int iTeamId, IEnumerable<InfrStadiumSector> eSectors) { IList<Sector> teamSectors = eSectors.ToList(); ... work with data } But attempt to launch query causes the following error: Expression of type 'System.Int32' cannot be used for constructor parameter of type 'System.Collections.Generic.IEnumerable`1[InfrStadiumSector]' Question 1: Could you please explain, what is wrong here, I don't understand why 'team_sectors' is applied as 'System.Int32'? I've tried to change query a little (replace IEnumerable with IQueryeable): IList<InfrStadium> stadiums = (from sector in DbContext.sectors group sector by sector.TeamId into team_sectors select new InfrStadium(team_sectors.Key, team_sectors.AsQueryable()) ).ToList(); with appropriate constructor: private InfrStadium(int iTeamId, IQueryeable<InfrStadiumSector> eSectors) { IList<Sector> teamSectors = eSectors.ToList(); ... work with data } In this case I've received another but similar error: Expression of type 'System.Int32' cannot be used for parameter of type 'System.Collections.Generic.IEnumerable1[InfrStadiumSector]' of method 'System.Linq.IQueryable1[InfrStadiumSector] AsQueryableInfrStadiumSector' Question 2: Actually, the same question: can't understand at all what is going on here... P.S. I have another to optimize query idea (describe here: Linq2Sql: query optimisation) but I would love to find a solution with 1 request to DB).

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  • Problem with "moveable-only types" in VC++ 2010

    - by Luc Touraille
    I recently installed Visual Studio 2010 Professional RC to try it out and test the few C++0x features that are implemented in VC++ 2010. I instantiated a std::vector of std::unique_ptr, without any problems. However, when I try to populate it by passing temporaries to push_back, the compiler complains that the copy constructor of unique_ptr is private. I tried inserting an lvalue by moving it, and it works just fine. #include <utility> #include <vector> int main() { typedef std::unique_ptr<int> int_ptr; int_ptr pi(new int(1)); std::vector<int_ptr> vec; vec.push_back(std::move(pi)); // OK vec.push_back(int_ptr(new int(2)); // compiler error } As it turns out, the problem is neither unique_ptr nor vector::push_back but the way VC++ resolves overloads when dealing with rvalues, as demonstrated by the following code: struct MoveOnly { MoveOnly() {} MoveOnly(MoveOnly && other) {} private: MoveOnly(const MoveOnly & other); }; void acceptRValue(MoveOnly && mo) {} int main() { acceptRValue(MoveOnly()); // Compiler error } The compiler complains that the copy constructor is not accessible. If I make it public, the program compiles (even though the copy constructor is not defined). Did I misunderstand something about rvalue references, or is it a (possibly known) bug in VC++ 2010 implementation of this feature?

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  • Fastest XML parser for small, simple documents in Java

    - by Varkhan
    I have to objectify very simple and small XML documents (less than 1k, and it's almost SGML: no namespaces, plain UTF-8, you name it...), read from a stream, in Java. I am using JAXP to process the data from my stream into a Document object. I have tried Xerces, it's way too big and slow... I am using Dom4j, but I am still spending way too much time in org.dom4j.io.SAXReader. Does anybody out there have any suggestion on a faster, more efficient implementation, keeping in mind I have very tough CPU and memory constraints? [Edit 1] Keep in mind that my documents are very small, so the overhead of staring the parser can be important. For instance I am spending as much time in org.xml.sax.helpers.XMLReaderFactory.createXMLReader as in org.dom4j.io.SAXReader.read [Edit 2] The result has to be in Dom format, as I pass the document to decision tools that do arbitrary processing on it, like switching code based on the value of arbitrary XPaths, but also extracting lists of values packed as children of a predefined node. [Edit 3] In any case I eventually need to load/parse the complete document, since all the information it contains is going to be used at some point. (This question is related to, but different from, http://stackoverflow.com/questions/373833/best-xml-parser-for-java )

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  • Existentials and Scrap your Boilerplate

    - by finnsson
    I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing existentials. I got the existential data type data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine existentials with Scrap your Boilerplate? If so: how do you implement gunfold for an existential data type?

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  • Programming an IPTV application- Client/Server

    - by Sumit Ghosh
    I am part of a team which has been given a task to deploy an IPTV solution for a company. The system has been architect-ed like this. There is Video capture card , which receives satellite signals from a satellite receiver. This video capture card is part of a windows 7 machine. The signals need to be trans coded here and passed to a streaming server which will be received by end users. The end users will be desktop users having a C#.NET application installed to view the channels. I am confused at the choice of server software as I have multiple choices - Windows Media Server, VideoLan (VLC project), or Flash Media Server, it also supports MPEG-2 HD. My main aim to be able to stream MPEG-2 channels with HD quality and encrypt the channels at the server end so that the streams can be protected. I know reversing is possible but it wont be easy as for every naive user with wireshark snooping my streams. If any of you here has ever done such an implementation please do suggest me the best technologies I should go for. Iam open to C#,C++ and other similar languages. Any help shall be deeply appreciated. edit: End Users shall be part of Internet and not necessarily a lan, reason for this question is internet doesn't support multicast like Lan, so I need some suggestions.

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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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  • When is a method eligible to be inlined by the CLR?

    - by Ani
    I've observed a lot of "stack-introspective" code in applications, which often implicitly rely on their containing methods not being inlined for their correctness. Such methods commonly involve calls to: MethodBase.GetCurrentMethod Assembly.GetCallingAssembly Assembly.GetExecutingAssembly Now, I find the information surrounding these methods to be very confusing. I've heard that the run-time will not inline a method that calls GetCurrentMethod, but I can't find any documentation to that effect. I've seen posts on StackOverflow on several occasions, such as this one, indicating the CLR does not inline cross-assembly calls, but the GetCallingAssembly documentation strongly indicates otherwise. There's also the much-maligned [MethodImpl(MethodImpOptions.NoInlining)], but I am unsure if the CLR considers this to be a "request" or a "command." Note that I am asking about inlining eligibility from the standpoint of contract, not about when current implementations of the JITter decline to consider methods because of implementation difficulties, or about when the JITter finally ends up choosing to inline an eligible method after assessing the trade-offs. I have read this and this, but they seem to be more focused on the last two points (there are passing mentions of MethodImpOptions.NoInlining and "exotic IL instructions", but these seem to be presented as heuristics rather than as obligations). When is the CLR allowed to inline?

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  • Thread management advice - Is TPL a good idea?

    - by Ian
    I'm hoping to get some advice on the use of thread managment and hopefully the task parallel library, because I'm not sure I've been going down the correct route. Probably best is that I give an outline of what I'm trying to do. Given a Problem I need to generate a Solution using a heuristic based algorithm. I start of by calculating a base solution, this operation I don't think can be parallelised so we don't need to worry about. Once the inital solution has been generated, I want to trigger n threads, which attempt to find a better solution. These threads need to do a couple of things: They need to be initalized with a different 'optimization metric'. In other words they are attempting to optimize different things, with a precedence level set within code. This means they all run slightly different calculation engines. I'm not sure if I can do this with the TPL.. If one of the threads finds a better solution that the currently best known solution (which needs to be shared across all threads) then it needs to update the best solution, and force a number of other threads to restart (again this depends on precedence levels of the optimization metrics). I may also wish to combine certain calculations across threads (e.g. keep a union of probabilities for a certain approach to the problem). This is probably more optional though. The whole system needs to be thread safe obviously and I want it to be running as fast as possible. I tried quite an implementation that involved managing my own threads and shutting them down etc, but it started getting quite complicated, and I'm now wondering if the TPL might be better. I'm wondering if anyone can offer any general guidance? Thanks...

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  • To use the 'I' prefix for interfaces or not to

    - by ng
    That is the question? So how big a sin is it not to use this convention when developing a c# project? This convention is widely used in the .NET class library. However, I am not a fan to say the least, not just for asthetic reasons but I don't think it makes any contribution. For example is IPSec an interface of PSec? Is IIOPConnection An interface of IOPConnection, I usually go to the definition to find out anyway. So would not using this convention cause confusion? Are there any c# projects or libraries of note that drop this convention? Do any c# projects that mix conventions, as unfortunately Apache Wicket does? The Java class libraries have existed without this for many years, I don't feel I have ever struggled to read code without it. Also, should the interface not be the most primitive description? I mean IList<T> as an interface for List<T> in c#, is it not better to have List<T> and LinkedList<T> or ArrayList<T> or even CopyOnWriteArrayList<T>? The classes describe the implementation? I think I get more information here, than I do from List<T> in c#.

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  • Multi-Precision Arithmetic on MIPS

    - by Rob
    Hi, I am just trying to implement multi-precision arithmetic on native MIPS. Assume that one 64-bit integer is in register $12 and $13 and another is in registers $14 and $15. The sum is to be placed in registers $10 and $11. The most significant word of the 64-bit integer is found in the even-numbered registers, and the least significant word is found in the odd-numbered registers. On the internet, it said, this is the shortest possible implementation. addu $11, $13, $15 # add least significant word sltu $10, $11, $15 # set carry-in bit addu $10, $10, $12 # add in first most significant word addu $10, $10, $14 # add in second most significant word I just wanna double check that I understand correctly. The sltu checks if the sum of the two least significant words is smaller or equal than one of the operands. If this is the case, than did a carry occur, is this right? To check if there occured a carry when adding the two most significant words and store the result in $9 I have to do: sltu $9, $10, $12 # set carry-in bit Does this make any sense?

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  • Why do Scala maps have poor performance relative to Java?

    - by Mike Hanafey
    I am working on a Scala app that consumes large amounts of CPU time, so performance matters. The prototype of the system was written in Python, and performance was unacceptable. The application does a lot with inserting and manipulating data in maps. Rex Kerr's Thyme was used to look at the performance of updating and retrieving data from maps. Basically "n" random Ints were stored in maps, and retrieved from the maps, with the time relative to java.util.HashMap used as a reference. The full results for a range of "n" are here. Sample (n=100,000) performance relative to java, smaller is worse: Update Read Mutable 16.06% 76.51% Immutable 31.30% 20.68% I do not understand why the scala immutable map beats the scala mutable map in update performance. Using the sizeHint on the mutable map does not help (it appears to be ignored in the tested implementation, 2.10.3). Even more surprisingly the immutable read performance is worse than the mutable read performance, more significantly so with larger maps. The update performance of the scala mutable map is surprisingly bad, relative to both scala immutable and plain Java. What is the explanation?

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  • Displaying modal view in Objective-C

    - by kpower
    I'm trying to display Modal View in my app. I have subclass of UIViewController that has only the "Done" button (UIButton created with IB and linked with XCode). .h @interface myModalVC : UIViewController { UIButton *bDone; } @property (nonatomic, retain) IBOutlet UIButton *bDone; - (IBAction)bDoneTouchDown:(id)sender; @end .m #import "myModalVC.h" @implementation myModalVC @synthesize bDone; - (void)dealloc { [bDone release]; [super dealloc]; } - (void)viewDidLoad { [super viewDidLoad]; } - (void)viewDidUnload { } - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return (UIInterfaceOrientationLandscapeLeft == interfaceOrientation || UIInterfaceOrientationLandscapeRight == interfaceOrientation); } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; } - (IBAction)bDoneTouchDown:(id)sender { [self.parentViewController dismissModalViewControllerAnimated:YES]; } @end I'm trying to display modal view with this code (from my main view): myModalVC *temp = [[[myModalVC alloc] initWithNibName:@"myModalVC" bundle:[NSBundle mainBundle]] autorelease]; [self presentModalViewController:temp animated:YES]; If this code is placed in some method, that responds to button touches - everything is fine. But when I place it to some other method (called during some processes in my app) - modal view is displayed without problems, but when I press (touch) "Done" button, application crashes with "Program received signal: “EXC_BAD_ACCESS”." What am I doing wrong?

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  • How to fix: unrecognized selector sent to instance

    - by Matt
    I am having a problem that may be simple to fix, but not simple for me to debug. I simple have a button inside a view in IB; the file's owner is set to the view controller class I am using and when making the connections, everything seems fine, ie. the connector is finding the method I am trying to call etc. however, I am receiving this error: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIApplication getStarted:]: unrecognized selector sent to instance 0x3d19130' My code is as follows: RootViewController.h @interface RootViewController : UIViewController { IBOutlet UIButton* getStartedButton; } @property (nonatomic, retain) UIButton* getStartedButton; - (IBAction) getStarted: (id)sender; @end RootViewController.m #import "RootViewController.h" #import "SimpleDrillDownAppDelegate.h" @implementation RootViewController @synthesize getStartedButton; - (void)viewDidLoad { [super viewDidLoad]; } - (IBAction) getStarted: (id)sender { NSLog(@"Button Tapped!"); //[self.view removeFromSuperview]; } - (void)dealloc { [getStartedButton release]; [super dealloc]; } @end Seems simple enough...any thoughs?

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  • With C# 3.0, how to write Interface based code with generic collection?

    - by Deecay
    I want to write code that is decouple and clean, and I know that by programming to an interface instead of the implementation, my code will be more flexible and extensible. So, instead of writing methods like: bool IsProductAvailable(ProductTypeA product); I write methods like: bool IsProductAvailable(IProduct product); As long as my products implement IProduct: class ProductTypeA : IProduct I should be OK. All is well until I start using generic collections. Since C# 3.0 doesn't support covariant and contravariant, even though both ProuctTypeA and ProductTypeB implements IProduct, you cannot put List in List. This is pretty troublesome because a lot of times I want to write something like: bool AreProductsAvailable(List<IProduct> products); So that I can check product avaialbility by writing: List<ProductA> productsArrived = GetDataFromDataabase(); bool result = AreProductsAvailable(productsArrived); And I want to write just one AreProductsAvailable() method that works with all IProduct collections. I know that C# 4.0 is going to support covariant and contravariant, but I also realize that there other libraries that seemed to have the problem solved. For instance, I was trying out ILOG Gantt the gantt chart control, and found that they have a lot of collection intefaces that looks like this: IActivityCollection ILinkCollection So it seems like their approach is wrapping the generic collection with an interface. So instead of "bool AreProductsAvailable(List products);", I can do: bool AreProductsAvailable(IProductCollection products); And then write some code so that IProductCollection takes whatever generic collection of IProduct, be it List or List. However, I don't know how to write an IProductCollection interface that does that "magic". :-< (ashame) .... Could someone shed me some light? This has been bugging me for so long, and I so wanted to do the "right thing". Well, thanks!

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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  • Javascript Getting Objects to Fallback to One Another

    - by Ian
    Here's a ugly bit of Javascript it would be nice to find a workaround. Javascript has no classes, and that is a good thing. But it implements fallback between objects in a rather ugly way. The foundational construct should be to have one object that, when a property fails to be found, it falls back to another object. So if we want a to fall back to b we would want to do something like: a = {sun:1}; b = {dock:2}; a.__fallback__ = b; then a.dock == 2; But, Javascript instead provides a new operator and prototypes. So we do the far less elegant: function A(sun) { this.sun = sun; }; A.prototype.dock = 2; a = new A(1); a.dock == 2; But aside from elegance, this is also strictly less powerful, because it means that anything created with A gets the same fallback object. What I would like to do is liberate Javascript from this artificial limitation and have the ability to give any individual object any other individual object as its fallback. That way I could keep the current behavior when it makes sense, but use object-level inheritance when that makes sense. My initial approach is to create a dummy constructor function: function setFallback(from_obj, to_obj) { from_obj.constructor = function () {}; from_obj.constructor.prototype = to_obj; } a = {sun:1}; b = {dock:2}; setFallback(a, b); But unfortunately: a.dock == undefined; Any ideas why this doesn't work, or any solutions for an implementation of setFallback? (I'm running on V8, via node.js, in case this is platform dependent)

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  • How SQLite on Android handles long strings?

    - by Levara
    I'm wondering how Android's implementation of SQLite handles long Strings. Reading from online documentation on sqlite, it said that strings in sqlite are limited to 1 million characters. My strings are definitely smaller. I'm creating a simple RSS application, and after parsing a html document, and extracting text, I'm having problem saving it to a database. I have 2 tables in database, feeds and articles. RSS feeds are correctly saved and retrieved from feeds table, but when saving to the articles table, logcat is saying that it cannot save extracted text to it's column. I don't know if other columns are making problems too, no mention of them in logcat. I'm wondering, since text is from an article on web, are signs like (",',;) creating problems? Is Android automaticaly escaping them, or I have to do that. I'm using a technique for inserting similar to one in notepad tutorial: public long insertArticle(long feedid, String title, String link, String description, String h1,tring h2, String h3, String p, String image, long date) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_FEEDID, feedid); initialValues.put(KEY_TITLE, title); initialValues.put(KEY_LINK, link); initialValues.put(KEY_DESCRIPTION, description ); initialValues.put(KEY_H1, h1 ); initialValues.put(KEY_H2, h2); initialValues.put(KEY_H3, h3); initialValues.put(KEY_P, p); initialValues.put(KEY_IMAGE, image); initialValues.put(KEY_DATE, date); return mDb.insert(DATABASE_TABLE_ARTICLES,null, initialValues); } Column P is for extracted text, h1, h2 and h3 are for headers from a page. Logcat reports only column p to be the problem. The table is created with following statement: private static final String DATABASE_CREATE_ARTICLES = "create table articles( _id integer primary key autoincrement, feedid integer, title text, link text not null, description text," + "h1 text, h2 text, h3 text, p text, image text, date integer);";

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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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