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  • Where to define a filter function for a form field in my Joomla component's preferences

    - by Herman
    I am creating a component in Joomla 2.5. This component has some options that are defined in its config.xml, so they can be set in the preferences of the component. Now I would like to apply a filter to one of these option fields, using the attribute filter="my_filter". In the source code of JForm I saw the following lines at the very end of the implementation of JForm::filterField(): if (strpos($filter, '::') !== false && is_callable(explode('::', $filter))) { $return = call_user_func(explode('::', $filter), $value); } elseif (function_exists($filter)) { $return = call_user_func($filter, $value); } That's what I needed for using a filter function defined by myself! I managed to do this for form fields used in the views of my component. I defined the filter function as MyComponentHelper::my_filter(), where MyComponentHelper is a helper class which I always load in the very base of my component. And in the form's xml I added filter="MyComponentHelper::my_filter" to the fields that have to be filtered. However... when I am trying to apply the filter function to a form field in my component's preferences, I am not in my own component, but in com_config instead, so my helper class is not available! So, therefore, my question: where to define my own filter function in such a way that it can be found and called by JForm::filterField() in com_config?? Help is very much appreciated.

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  • @selector and return value

    - by user320926
    The idea it's very easy, i have an http download class, this class must support the http authentication but it's basically a background thread so i would like to avoid to prompt directly to the screen, i would like to use a delegate method to require from outside of the class, like a viewController. But i don't know if is possible or if i have to use a different syntax. This class use this delegate protocol: //Updater.h @protocol Updater <NSObject> -(NSDictionary *)authRequired; @optional -(void)statusUpdate:(NSString *)newStatus; -(void)downloadProgress:(int)percentage; @end @interface Updater : NSThread { ... } This is the call to the delegate method: //Updater.m // This check always fails :( if ([self.delegate respondsToSelector:@selector(authRequired:)]) { auth = [delegate authRequired]; } This is the implementation of the delegate method //rootViewController.m -(NSDictionary *)authRequired; { // TODO: some kind of popup or modal view NSMutableDictionary *ret=[[NSMutableDictionary alloc] init]; [ret setObject:@"utente" forKey:@"user"]; [ret setObject:@"password" forKey:@"pass"]; return ret; }

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  • Determine target architecture of binary file in Linux (library or executable)

    - by Fernando Miguélez
    We have an issue related to a Java application running under a (rather old) FC3 on a Advantech POS board with a Via C3 processor. The java application has several compiled shared libs that are accessed via JNI. Via C3 processor is suppossed to be i686 compatible. Some time ago after installing Ubuntu 6.10 on a MiniItx board with the same processor I found out that the previous statement is not 100% true. The Ubuntu kernel hanged on startup due to the lack of some specific and optional instructions of the i686 set in the C3 processor. These instructions missing in C3 implementation of i686 set are used by default by GCC compiler when using i686 optimizations. The solution in this case was to go with a i386 compiled version of Ubuntu distribution. The base problem with the Java application is that the FC3 distribution was installed on the HD by cloning from an image of the HD of another PC, this time an Intel P4. Afterwards the distribution needed some hacking to have it running such as replacing some packages (such as the kernel one) with the i383 compiled version. The problem is that after working for a while the system completely hangs without a trace. I am afraid that some i686 code is left somewhere in the system and could be executed randomly at any time (for example after recovering from suspend mode or something like that). My question is: Is there any tool or way to find out at what specific architecture is an binary file (executable or library) aimed provided that "file" does not give so much information?

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  • Very very weird problem with UIImageView property - I can access it then I can't, and it's not nil.

    - by just_another_coder
    Very very weird problem with UIImageView property on iPad application @interface MyViewController : UIViewController { IBOutlet UIImageView* coverImage; } @property(nonatomic, retain) IBOutlet UIImageView* coverImage; … more code @implementation MyViewController @synthesize coverImage; … more code - (void)viewDidLoad { [super viewDidLoad]; NSString* imageName = @"my_image.png"; UIImage* tempImage = [UIImage imageNamed:imageName]; [self.coverImage setImage:tempImage]; } The above code WILL display the image. In another part of code: -(IBAction) stopButtonPressed:(id)sender { [self.coverImage setHidden:YES]; NSLog(@"coverImage desc: %@", [coverImage description]); } The image will NOT disappear. I know the reference to the image isn't nil, because it gives me this output: 2010-05-29 17:37:40.706 MyApp[95360:207] coverImage desc: UIImageView: 0x5128420; frame = (0 0; 1024 768); autoresize = RM+BM; userInteractionEnabled = NO; layer = CALayer: 0x512bed0 In addition, if I move the code in viewDidLoad to another part of the class, and try to execute it from there, it fails to show the image at all.

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  • UDP server doesnt accept calls from outside.

    - by rayman
    Hi, ive implement simple udp server on my Android device.(sdk 1.5) it works fine when i am runnning a local client on the phone sends through it trigger to my server. but when i try to get udp call from an outside server to my phone, it doesnt work. already make sure the outside server isnt blocked by firewall and it's sending the udp trigger to the right port, which my phone is listening to. i used natstat on the phone and checked that the phone is realy listening to the it's local ip and the port ive setted it to. here is my code of the server:(on the device) // server will listen to one client try { Thread udpServerThread = new Thread() { @Override public void run() { try { // Retrieve the ServerName InetAddress serverAddr = InetAddress .getByName("localhost"); Log.d("UDP", "S: Connecting..."); // Create new UDP-Socket socket = new DatagramSocket(SERVERPORT,serverAddr); byte[] buf = new byte[17]; // * Prepare a UDP-Packet that can contain the data we // * want to receive DatagramPacket packet = new DatagramPacket(buf, buf.length); Log.d("UDP", "S: Receiving..."); // wait to Receive the UDP-Packet socket.receive(packet); Log.d("UDP", "S: Received: '" + new String(packet.getData()) + "'"); acceptedMsg=new String(packet.getData()); notifyService(acceptedMsg); Log.d("UDP", "S: Done."); } catch (Exception e) { Log.e("UDP", "S: Error", e); } } }; udpServerThread.start(); } catch (Exception E) { Log.e("r",E.getMessage()) ; } so as i said, when i try it with local client(seperate thread) which sends udp trigger it works fine, but when i take this client implementation and put it on an outside real server, after UDP being sent, the phone doesnt respond to it. any idea? thanks, ray.

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  • Design pattern to integrate Rails with a Comet server

    - by empire29
    I have a Ruby on Rails (2.3.5) application and an APE (Ajax Push Engine) server. When records are created within the Rails application, i need to push the new record out on applicable channels to the APE server. Records can be created in the rails app by the traditional path through the controller's create action, or it can be created by several event machines that are constantly monitoring various inputstream and creating records when they see data that meets a certain criteria. It seems to me that the best/right place to put the code that pushes the data out to the APE server (which in turn pushes it out to the clients) is in the Model's after_create hook (since not all record creations will flow through the controller's create action). The final caveat is I want to push a piece of formatted HTML out to the APE server (rather than a JSON representation of the data). The reason I want to do this is 1) I already have logic to produce the desired layout in existing partials 2) I don't want to create a javascript implementation of the partials (javascript that takes a JSON object and creates all the HTML around it for presentation). This would quickly become a maintenance nightmare. The problem with this is it would require "rendering" partials from within the Model (which im having trouble doing anyhow because they don't seem to have access to Helpers when they're rendered in this manner). Anyhow - Just wondering what the right way to go about organizing all of this is. Thanks

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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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  • 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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  • 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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  • MSMQ - Message Queue Abstraction and Pattern

    - by Maxim Gershkovich
    Hi All, Let me define the problem first and why a messagequeue has been chosen. I have a datalayer that will be transactional and EXTREMELY insert heavy and rather then attempt to deal with these issues when they occur I am hoping to implement my application from the ground up with this in mind. I have decided to tackle this problem by using the Microsoft Message Queue and perform inserts as time permits asynchronously. However I quickly ran into a problem. Certain inserts that I perform may need to be recalled (ie: retrieved) immediately (imagine this is for POS system and what happens if you need to recall the last transaction - one that still hasn’t been inserted). The way I decided to tackle this problem is by abstracting the MessageQueue and combining it in my data access layer thereby creating the illusion of a single set of data being returned to the user of the datalayer (I have considered the other issues that occur in such a scenario (ie: essentially dirty reads and such) and have concluded for my purposes I can control these issues). However this is where things get a little nasty... I’ve worked out how to get the messages back and such (trivial enough problem) but where I am stuck is; how do I create a generic (or at least somewhat generic) way of querying my message queue? One where I can minimize the duplication between the SQL queries and MessageQueue queries. I have considered using LINQ (but have very limited understanding of the technology) and have also attempted an implementation with Predicates which so far is pretty smelly. Are there any patterns for such a problem that I can utilize? Am I going about this the wrong way? Does anyone have an of their own ideas about how I can tackle this problem? Does anyone even understand what I am talking about? :-) Any and ALL input would be highly appreciated and seriously considered… Thanks again.

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  • How to store and remove dynamically and automatic variable of generic data type in custum list data

    - by Vineel Kumar Reddy
    Hi I have created a List data structure implementation for generic data type with each node declared as following. struct Node { void *data; .... .... } So each node in my list will have pointer to the actual data(generic could be anything) item that should be stored in the list. I have following signature for adding a node to the list AddNode(struct List *list, void* eledata); the problem is when i want to remove a node i want to free even the data block pointed by *data pointer inside the node structure that is going to be freed. at first freeing of datablock seems to be straight forward free(data) // forget about the syntax..... But if data is pointing to a block created by malloc then the above call is fine....and we can free that block using free function int *x = (int*) malloc(sizeof(int)); *x = 10; AddNode(list,(void*)x); // x can be freed as it was created using malloc what if a node is created as following int x = 10; AddNode(list,(void*)&x); // x cannot be freed as it was not created using malloc Here we cannot call free on variable x!!!! How do i know or implement the functionality for both dynamically allocated variables and static ones....that are passed to my list.... Thanks in advance...

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  • Java Input/Output streams for unnamed pipes created in native code?

    - by finrod
    Is there a way to easily create Java Input/Output streams for unnamed pipes created in native code? Motivation: I need my own implementation of the Process class. The native code spawns me a new process with subprocess' IO streams redirected to unnamed pipes. Problem: The file descriptors for correct ends of those pipes make their way to Java. At this point I get stuck as I cannot create a new FileDescriptor which I could pass to FileInput/FileOutput stream. I have used reflection to get around the problem and got communication with a simple bouncer sub-process running. However I have a notion that it is not the cleanest way to go. Have you used this approach? Do you see any problems with this approach? (the platform will never change) Searching around the internets revealed similar solution using native code. Any thoughts before I dive into heavy testing of this approach are very welcome. I would like to give a shot to existing code before writing my own IO stream implementations... Thank you.

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  • Can't touch UITextField on UIScrollView

    - by Chris B
    Hey guys, I know this has been talked about a lot. I think I've gone thru every question on this site, and still have not been able to get this working. I'm new to developing but I have a good sense of what's going on with all of my code. I definitely don't have a lot of experience though, this is my first iPhone app. I'm making a data entry field that is comprised of multiple UITextFields within a UIScrollView. I'll avoid explaining the other details for now, as it seems its a very basic problem. Without a scrollview, the textfields work perfectly. I can touch the textfield and the keyboard or picker view show up appropriately. When I add the textfields to a scrollview, the scrollview works, but then the text fields don't receive my touches. Here's the key: When 'User Interaction' is ENABLED, the scrollview works but the textfield touches are NOT registered. When 'User Interaction' is DISABLED, the scrollview doesn't work, but the textfield touches ARE registered and the keyboard/picker pops up. From the other posts I have seen people creating subclasses and overriding the touches in a separate implementation. I've seen people using custom content views (subviews?), I've seen some solutions that are now obsolete since the APIs have changed in newer versions of the SDK, and I am just completely stuck. I will leave out my code for now, because maybe there is a solution that someone has without requiring my code. If someone needs to see my code, I will put it up. My app is being written in the 3.1.3 SDK. If anyone has ANY information that could help, it would be so greatly appreciated.

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  • Orientation issue while presenting Modal ViewController

    - by Jacky Boy
    Current scenario: Right now I am showing a UIViewController using a segue with the style Modal and presentation Sheet. This Modal gets its superview bounds change, in order to have the dimensions I want, like this: - (void)viewWillLayoutSubviews { [super viewWillLayoutSubviews]; self.view.superview.bounds = WHBoundsRect; } The only allowed orientations are UIInterfaceOrientationLandscapeLeft and UIInterfaceOrientationLandscapeRight. Since the Modal has some TextFields and the keyboard would be over the Modal itself, I am changing its center so it moves a bit to the top. The problem: What I am noticing right now, is that I am unable to work with the Y coordinate. In order for it move vertically (remember it's on landscape) I need to work with the X. The problem is that when it's UIInterfaceOrientationLandscapeLeft I need to come with a negative X. And when it's UIInterfaceOrientationLandscapeRight I need to come with a positive X. So it seems that the X/Y Coordinate System is "glued" to the top left corner while in Portrait and when an orientation occurs, it's still there: What I have done So I have something like this: UIInterfaceOrientation orientation = [[UIApplication sharedApplication] statusBarOrientation]; NSInteger newX = 0.0f; if (orientation == UIInterfaceOrientationLandscapeLeft) { // Logic for calculating the negative X. } else { // Logic for calculating the positive X. } It works exactly like I want, but it seems a very fragile implementation. Am I missing something? Is this the expected behaviour?

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  • Partial class or "chained inheritance"

    - by Charlie boy
    Hi From my understanding partial classes are a bit frowned upon by professional developers, but I've come over a bit of an issue; I have made an implementation of the RichTextBox control that uses user32.dll calls for faster editing of large texts. That results in quite a bit of code. Then I added spellchecking capabilities to the control, this was made in another class inheriting RichTextBox control as well. That also makes up a bit of code. These two functionalities are quite separate but I would like them to be merged so that I can drop one control on my form that has both fast editing capabilities and spellchecking built in. I feel that simply adding the code form one class to the other would result in a too large code file, especially since there are two very distinct areas of functionality, so I seem to need another approach. Now to my question; To merge these two classes should I make the spellchecking RichTextBox inherit from the fast edit one, that in turn inherits RichTextBox? Or should I make the two classes partials of a single class and thus making them more “equal” so to speak? This is more of a question of OO principles and exercise on my part than me trying to reinvent the wheel, I know there are plenty of good text editing controls out there. But this is just a hobby for me and I just want to know how this kind of solution would be managed by a professional. Thanks!

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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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  • Model class for NSDictionary information with Lazy Loading

    - by samfu_1
    My application utilizes approx. 50+ .plists that are used as NSDictionaries. Several of my view controllers need access to the properties of the dictionaries, so instead of writing duplicate code to retrieve the .plist, convert the values to a dictionary, etc, each time I need the info, I thought a model class to hold the data and supply information would be appropriate. The application isn't very large, but it does handle a good deal of data. I'm not as skilled in writing model classes that conform to the MVC paradigm, and I'm looking for some strategies for this implementation that also supports lazy loading.. This model class should serve to supply data to any view controller that needs it and perform operations on the data (such as adding entries to dictionaries) when requested by the controller functions currently planned: returning the count on any dictionary adding one or more dictionaries together Currently, I have this method for supporting the count lookup for any dictionary. Would this be an example of lazy loading? -(NSInteger)countForDictionary: (NSString *)nameOfDictionary { NSBundle *bundle = [NSBundle mainBundle]; NSString *plistPath = [bundle pathForResource: nameOfDictionary ofType: @"plist"]; //load plist into dictionary NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] initWithContentsOfFile: plistPath]; NSInteger count = [dictionary count] [dictionary release]; [return count] }

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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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  • Jquery Apache - IE problem

    - by Soldierflup
    I'm having a button tag on my page with a value. <button class='btn' value='value'>show value</button> I have this jquery code : $('.btn').click(function() { var w = 'value = '+$(this).val()+' / text = '+$(this).html(); alert(w); }); In FF, no problem the result is ok (display: value = value / text = show value). The problem comes with IE8 which displays a different results from my testing server and the production server. The testing server is my local machine with a standard XAMPP installation. The productionserver is a server based on linux with apache, php and mysql. Result from the testing server is ok (display like FF), the result from the production server is not good (displaying : value = show value / text : show value). Anyone an idea if it is apache that causes the error ? I know there are some issues with the use of val() because IE is considering it as an attribute and not a value. The problem is that changing the jQuery from val() to attr('value') is quit a lot of work (this implementation is already on a lot of pages) and I think it could be much easier to change something on the webserver.

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  • Prove correctness of unit test

    - by Timo Willemsen
    I'm creating a graph framework for learning purposes. I'm using a TDD approach, so I'm writing a lot of unit tests. However, I'm still figuring out how to prove the correctness of my unit tests For example, I have this class (not including the implementation, and I have simplified it) public class SimpleGraph(){ //Returns true on success public boolean addEdge(Vertex v1, Vertex v2) { ... } //Returns true on sucess public boolean addVertex(Vertex v1) { ... } } I also have created this unit tests @Test public void SimpleGraph_addVertex_noSelfLoopsAllowed(){ SimpleGraph g = new SimpleGraph(); Vertex v1 = new Vertex('Vertex 1'); actual = g.addVertex(v1); boolean expected = false; boolean actual = g.addEdge(v1,v1); Assert.assertEquals(expected,actual); } Okay, awesome it works. There is only one crux here, I have proved that the functions work for this case only. However, in my graph theory courses, all I'm doing is proving theorems mathematically (induction, contradiction etc. etc.). So I was wondering is there a way I can prove my unit tests mathematically for correctness? So is there a good practice for this. So we're testing the unit for correctness, instead of testing it for one certain outcome.

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  • Memory leaks after using typeinfo::name()

    - by icabod
    I have a program in which, partly for informational logging, I output the names of some classes as they are used (specifically I add an entry to a log saying along the lines of Messages::CSomeClass transmitted to 127.0.0.1). I do this with code similar to the following: std::string getMessageName(void) const { return std::string(typeid(*this).name()); } And yes, before anyone points it out, I realise that the output of typeinfo::name is implementation-specific. According to MSDN The type_info::name member function returns a const char* to a null-terminated string representing the human-readable name of the type. The memory pointed to is cached and should never be directly deallocated. However, when I exit my program in the debugger, any "new" use of typeinfo::name() shows up as a memory leak. If I output the information for 2 classes, I get 2 memory leaks, and so on. This hints that the cached data is never being freed. While this is not a major issue, it looks messy, and after a long debugging session it could easily hide genuine memory leaks. I have looked around and found some useful information (one SO answer gives some interesting information about how typeinfo may be implemented), but I'm wondering if this memory should normally be freed by the system, or if there is something i can do to "not notice" the leaks when debugging. I do have a back-up plan, which is to code the getMessageName method myself and not rely on typeinfo::name, but I'd like to know anyway if there's something I've missed.

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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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  • XSD: Different sub-elements depending on attribute/element value

    - by AndiDog
    Another XSD question - how can I achieve that the following XML elements are both valid: <some-element> <type>1</type> <a>...</a> </some-element> <some-element> <type>2</type> <b>...</b> </some-element> The sub-elements (either <a> or <b>) should depend on the content of <type> (could also be an attribute). It would be so simple in RelaxNG - but RelaxNG doesn't support key integrity :( Is there a way to implement this in XSD? Note: XML schema version 1.1 supports <xs:alternative>, which might be a solution, but afaik no reference implementation (e.g. libxml2) supports this yet. So I'm searching for workarounds. The only way I've come up with is: <type>1</type> <some-element type="1"> <!-- simple <xs:choice> between <a> and <b> goes here --> <a>...</a> </some-element> <!-- and now create a keyref between <type> and @type -->

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  • Are there any downsides in using C++ for network daemons?

    - by badcat
    Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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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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