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• When is Googling it wrong?

  - by Drahcir

  I've been going through Stack Overflow for quite a bit now and noticed certain people (usually experienced programmers) frown upon Googling (researching) certain problems. Since I myself tend to use Google quite a bit to solve certain programming related issues I found certain comments rather demoralising. Now some of you may have come here trigger happy to delete this post but I needed some clarification. I usually Google things that usually syntax related that I would have never figured out on my own. For example I once wondered how to access the properties of a class that I didn't have a direct relationship to. So after a bit of research I discovered reflection and got what I wanted. Now in another scenario is learning a new language, in my case Silverlight were it differs in certain aspects of .NET compared to say ASP.NET. A few weeks ago I had no idea how to load another Silverlight page (usercontrol) and had to Google my way to the solution which I found wasn't as simple as I had imagined. In scenario three is were I myself frown up, that is just stealing a huge chunk of code to avoid doing the work yourself, for example paging a HTML table using JavaScript, where one just copies and pastes the JavasSript code without as much as trying to understand how it works. I do admit I have done this once or twice before for trivial tasks that had very little time limit and weren't all that important but most of the time still have to throw away what I found because it took too much time to adapt it and get what I wanted out of it. In the last scenario, I sometimes have a piece of code that I would be really unhappy about, as in I find it sloppy or too overcomplicated and try to look on the Internet to see other ways to tackle the same problem, let's say filtering through a table. With the knowledge I acquire I learned new coding practices that help me work more efficiently like "Do not repeat yourself" and such. Now in your opinion when do you find it wrong to use Google (or any other researching tool) to find a solution to your problem?

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• C++ destructor problem with boost::scoped_ptr

  - by bb-generation

  I have a question about the following code: #include <iostream> #include <boost/scoped_ptr.hpp> class Interface { }; class A : public Interface { public: A() { std::cout << "A()" << std::endl; } virtual ~A() { std::cout << "~A()" << std::endl; } }; Interface* get_a() { A* a = new A; return a; } int main() { { std::cout << "1" << std::endl; boost::scoped_ptr<Interface> x(get_a()); std::cout << "2" << std::endl; } std::cout << "3" << std::endl; } It creates the following output: 1 A() 2 3 As you can see, it doesn't call the destructor of A. The only way I see to get the destructor of A being called, is to add a destructor for the Interface class like this: virtual ~Interface() { } But I really want to avoid any Implementation in my Interface class and virtual ~Interface() = 0; doesn't work (produces some linker errors complaining about a non existing implementation of ~Interface(). So my question is: What do I have to change in order to make the destructor being called, but (if possible) leave the Interface as an Interface (only abstract methods).

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• What's the correct place to share application logic in CakePHP?

  - by Pichan

  I guess simple answer to the question would be a component. Although I agree, I feel weird having to write a component for something so specific. For example, let's say I have a table of users. When a user is created, it should form a chain reaction of events, initiating different kinds of data related to the user all around the database. I figured it would be best to avoid directly manipulating the database from different controllers and instead pack all that neatly in a method. However since some logic needs to be accesed separately, I really can't have the whole package in a single method. Instead I thought it would be logical to break it up to smaller pieces(like $userModelOrController->createNew() and $candyStorageModelOrController->createNew()) that only interact with their respective database table. Now, if the logic is put to the model, it works great until I need to use other models. Of course it's possible, but when compared to loading models in a controller, it's not that simple. It's like a Cake developer telling me "Sure, it's possible if you want to do it that way but that's not how I would do it". Then, if the logic is put to the controller, I can access other models really easy through $this->loadModel(), but that brings me back to the previously explained situation since I need to be able to continue the chain reaction indefinitely. Accessing other controllers from a controller is possible, but again there doesn't seem to be any direct way of doing so, so I'm guessing I'm still not doing it right. By using a component this problem could be solved easily, since components are available to every controller I want. But like I wrote at the beginning, it feels awkward to create a component specifically for this one task. To me, components seem more like packages of extra functionality(like the core components) and not something to share controller-specific logic. Since I'm new to this whole MVC thing, I could've completely misunderstood the concept. Once again, I would be thankful if someone pointed me to the right direction :)

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• algorithm to find longest non-overlapping sequences

  - by msalvadores

  I am trying to find the best way to solve the following problem. By best way I mean less complex. As an input a list of tuples (start,length) such: [(0,5),(0,1),(1,9),(5,5),(5,7),(10,1)] Each element represets a sequence by its start and length, for example (5,7) is equivalent to the sequence (5,6,7,8,9,10,11) - a list of 7 elements starting with 5. One can assume that the tuples are sorted by the start element. The output should return a non-overlapping combination of tuples that represent the longest continuos sequences(s). This means that, a solution is a subset of ranges with no overlaps and no gaps and is the longest possible - there could be more than one though. For example for the given input the solution is: [(0,5),(5,7)] equivalent to (0,1,2,3,4,5,6,7,8,9,10,11) is it backtracking the best approach to solve this problem ? I'm interested in any different approaches that people could suggest. Also if anyone knows a formal reference of this problem or another one that is similar I'd like to get references. BTW - this is not homework. Edit Just to avoid some mistakes this is another example of expected behaviour for an input like [(0,1),(1,7),(3,20),(8,5)] the right answer is [(3,20)] equivalent to (3,4,5,..,22) with length 20. Some of the answers received would give [(0,1),(1,7),(8,5)] equivalent to (0,1,2,...,11,12) as right answer. But this last answer is not correct because is shorter than [(3,20)].

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• Question about array subscripting in C#

  - by Michael J

  Back in the old days of C, one could use array subscripting to address storage in very useful ways. For example, one could declare an array as such. This array represents an EEPROM image with 8 bit words. BYTE eepromImage[1024] = { ... }; And later refer to that array as if it were really multi-dimensional storage BYTE mpuImage[2][512] = eepromImage; I'm sure I have the syntax wrong, but I hope you get the idea. Anyway, this projected a two dimension image of what is really single dimensional storage. The two dimensional projection represents the EEPROM image when loaded into the memory of an MPU with 16 bit words. In C one could reference the storage multi-dimensionaly and change values and the changed values would show up in the real (single dimension) storage almost as if by magic. Is it possible to do this same thing using C#? Our current solution uses multiple arrays and event handlers to keep things synchronized. This kind of works but it is additional complexity that we would like to avoid if there is a better way.

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• Flex 3 - Remove image flickering

  - by BS_C3

  Hello Community! I have an application with different components that are accessible through a viewstack in the main application. The main application looks like that: <Application> <Viewstack> <myComponent1/> <myComponent2/> <myComponent3/> . . . </Viewstack> </Application> In myComponent1, I have a horizontalList where the user can select a product. In myComponent2, I have 2 containers inside the component. A left container with a larger image of the product selected in myComponent1 and a right container with all characteristics of the product. Both containers have an embed background image. When I select a product in myComponent1, the application displays myComponent2. When the component is displayed, I first see the page without the large image of the product, then both containers flickers and the product image is displayed. How could I avoid this flickering? It's really annoying _< Thanks in advance for your help =) Regards. BS_C3

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• Apache Cordova (Phonegap): is jsop needed for cross-site scripting?

  - by DEX

  I've just started using Apache Cordova. I have an library that makes calls (via ajax) to a soap server. When I run these on my local machine in chrome, I get cross site scripting errors when trying to make calls to the service. When I run the same exact code using the Cordova browser in the iOS emulator, the scripts seem to hit the server fine and the response data is received properly. So my question is how is the Cordova browser able to make these requests without cross-site scripting permissions & JSONP ? One thing I noticed is that when the request is sent from iOS, there is no "Origin" header. Is this allowing the Cordova browser to stealthily circumvent cross-site scripting requirements? Is it possible that the node.js server on the device (I believe this is how Cordova works) is manipulating the headers to allow this? I'd like to avoid enabling cross-site scripting on my site so I think this "feature" is nice, but I'm wondering if it's a security hole as well. Anyone have experience with this?

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• The right approach to loading dynamic content into a UITableView in iOS

  - by OS.

  ok, I've read tons of bits and pieces on the subject of loading dynamic content (from the web) into a UITableView and the problem with calculating cell height upfront. I've tried different simple implementations but the problem persists... Assuming I need to read a JSON file from the web, parse it into 'item' objects, each with variable size image and various text labels, here is what I believe would be the right approach to avoid long hang time of the app while everything is loading: on app load read JSON file and parse into items array provide only small part of the items array to the tableview (about 10 items) - since I need to load the images associated with each item to calculate cell height - I don't want the view to go through the whole items list and load all images - this hangs the app until every image is loaded display the tableview with the available cells (assuming I load a few 'spare' ones, user can even scroll to more items) in the background using Grand Central Dispatch download images for all/some of the remaining items and then reload the tableview with the new data (repeat step 4 if item list is very long) Step 2 above is necessary since I have no way to calculate the cell height without loading the images first, and since tableview first calculates height of all cells it may take a very long time to download all images for all items. Would you say this is the right approach? am I missing something?

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• Multiple "ObjectChangeTracker" getting created, can it be avoided?

  - by user555937

  Hi, We are working on a POC where we have following architecture (MVVM), WPF(Client) + WCF + Model(DataAccess)+ ADO.Net Entity Framework 4.0 (with SQL Server 2008 R2 as DB) All are different projects. In the DataAccess layer we have created different Entity Models(edmx) based on the functionality. The tables under perticular flow are grouped and created different entity models. We are using self tracking entities to and fro to communicate with the WPF client through wcf service. For Single model everything works fine. But when we created a Multiple models then few issues started coming. Mutliple models have few duplicate tables/entities. Two probels are, 1) When we try to access entities from different models mutiple objects "ObjectChangeTracker" are getting created. E.g. CompanyModel(edmx) - Company(Entity) - ObjectChangeTracker, ObjectState ProductModel(edmx) - Customer(Entity) - ObjectChangeTracker1, ObjectState1 OrderModel(edmx) - Oder(Entity) - ObjectChangeTracker2, ObjectState2 Is there any way to avoid this? 2) There are few tables which shared across the Models, E.g. Company(Entity) is used in All above mdoels. During compile time it does not thow any error. But run time It gives error saying "Schema specified is not valid. Errors: The mapping of CLR type to EDM type is ambiguous because multiple CLR types match the EDM type "Company"".. To resolve this, we renamed the entities with some prefix to make them Unique. Is there any other way we can resolve this without changing the name of the entity in the same assembly? Thanks in advance and appreciate if anyone has approach for these issues. Thanks, Kiran

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• Generating different randoms valid for a day on different independent devices?

  - by Pentium10

  Let me describe the system. There are several mobile devices, each independent from each other, and they are generating content for the same record id. I want to avoid generating the same content for the same record on different devices, for this I though I would use a random and make it so too cluster the content pool based on these randoms. Suppose you have choices from 1 to 100. Day 1 Device#1 will choose for the record#33 between 1-10 Device#2 will choose for the record#33 between 40-50 Device#3 will choose for the record#33 between 50-60 Device#1 will choose for the record#55 between 40-50 Device#2 will choose for the record#55 between 1-10 Device#3 will choose for the record#55 between 10-20 Device#1 will choose for the record#11 between 1-10 Device#2 will choose for the record#22 between 1-10 Device#3 will choose for the record#99 between 1-10 Day 2 Device#1 will choose for the record#33 between 90-100 Device#2 will choose for the record#33 between 1-10 Device#3 will choose for the record#33 between 50-60 They don't have access to a central server. Data available for each of them: IMEI (unique per mobile) Date of today (same on all devices) Record id (same on all devices) What do you think, how is it possible? ps. tags can be edited

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• Void* array casting to float, int32, int16, etc.

  - by Griffin

  Hey guys, I've got an array of PCM data, it could be 16 bit, 24 bit packed, 32 bit, etc.. It could be signed, or unsigned, and it could be 32 or 64 bit floating point. It is currently stored as a "void**" matrix, indexed by channel, then by frame. The goal is to allow my library to take in any PCM format and buffer it, without requiring manipulation of the data to fit a designated structure. If the A/D converter spits out 24 bit packed arrays of interleaved PCM, I need to accept it gracefully. I also need to support 16 bit non interleaved, as well as any permutation of the above formats. I know the bit depth and other information at runtime, and I'm trying to code efficiently while not duplicating code. What I need is an effective way to cast the matrix, put PCM data into the matrix, and then pull it out later. I can cast the matrix to int32_t, or int16_t for the 32 and 16 bit signed PCM respectively, I'll probably have to store the 24 bit PCM in an int32_t for 32 bit, 8 bit byte systems as well. Can anyone recommend a good way to put data into this array, and pull it out later? I'd like to avoid large sections of code which look like: switch( mFormat ) { case 1: // unsigned 8 bit for( int i = 0; i < mChannels; i++ ) framesArray = (uint8_t*)pcm[i]; break; case 2: // signed 8 bit for( int i = 0; i < mChannels; i++ ) framesArray = (int8_t*)pcm[i]; break; case 3: // unsigned 16 bit ... Limitations: I'm working in C/C++, no templates, no RTTI, no STL. Think embedded. Things get trickier when I have to port this to a DSP with 16 bit bytes. Does anybody have any useful macros they might be willing to share? Thanks, -Griff

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• Test the sequentiality of a column with a single SQL query

  - by LauriE

  Hey, I have a table that contains sets of sequential datasets, like that: ID set_ID some_column n 1 'set-1' 'aaaaaaaaaa' 1 2 'set-1' 'bbbbbbbbbb' 2 3 'set-1' 'cccccccccc' 3 4 'set-2' 'dddddddddd' 1 5 'set-2' 'eeeeeeeeee' 2 6 'set-3' 'ffffffffff' 2 7 'set-3' 'gggggggggg' 1 At the end of a transaction that makes several types of modifications to those rows, I would like to ensure that within a single set, all the values of "n" are still sequential (rollback otherwise). They do not need to be in the same order according to the PK, just sequential, like 1-2-3 or 3-1-2, but not like 1-3-4. Due to the fact that there might be thousands of rows within a single set I would prefer to do it in the db to avoid the overhead of fetching the data just for verification after making some small changes. Also there is the issue of concurrency. The way locking in InnoDB (repeatable read) works (as I understand) is that if I have an index on "n" then InnoDB also locks the "gaps" between values. If I combine set_ID and n to a single index, would that eliminate the problem of phantom rows appearing? Looks to me like a common problem. Any brilliant ideas? Thanks! Note: using MySQL + InnoDB

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• Using custom Qt subclasses in Python

  - by kwatford

  First off: I'm new to both Qt and SWIG. Currently reading documentation for both of these, but this is a time consuming task, so I'm looking for some spoilers. It's good to know up-front whether something just won't work. I'm attempting to formulate a modular architecture for some in-house software. The core components are in C++ and exposed via SWIG to Python for experimentation and rapid prototyping of new components. Qt seems like it has some classes I could use to avoid re-inventing the wheel too much here, but I'm concerned about how some of the bits will fit together. Specifically, if I create some C++ classes, I'll need to expose them via SWIG. Some of these classes likely subclass Qt classes or otherwise have Qt stuff exposed in their public interfaces. This seems like it could raise some complications. There are already two interfaces for Qt in Python, PyQt and PySide. Will probably use PySide for licensing reasons. About how painful should I expect it to be to get a SWIG-wrapped custom subclass of a Qt class to play nice with either of these? What complications should I know about upfront?

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• Jquery Dialog - Is there a way to open it without registering it using .dialog?

  - by Raja

  This is my problem. I have a page with multiple tabs. I load those tabs dynamically and one of those tabs is a message container (mail). Every time I click a folder link (Inbox, Sent Mail etc) I reload just that tab alone with appropriate content. I use Jquery dialog to pick contacts and I have to load contacts everytime. Since I reload the whole tab content every time JQuery Dialog registers (or creates) the whole div content. To avoid this I did this: if ($("#ui-dialog-title-divContacts").length == 0) { //if dialog data is not created then make dialog $("#divContacts").dialog({ bgiframe: true, resizable: false, autoOpen: false, height: 600, width: 425, modal: true, overlay: { backgroundColor: '#000', opacity: 0.5 }, buttons: { Cancel: function () { //basically do nothing $(this).dialog("close"); }, 'Done': function () { $("#divTo").empty().html($("#divSelectedContacts").html()); $(this).dialog("close"); } } }); } I went to generated viewsource in FF and found that only one instance is being created. My problem now is it is not showing the dialog. Is there a way by which I can open this dialog without registering it. Any help is much appreciated.

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• streaming xml pretty printer in C/C++ using expat or libxml2?

  - by Mark Zeren

  I have a library that outputs xml without whitespace all on one line. In some cases I'd like to pretty print that output. I'm looking for a BSD-ish licensed C/C++ library or sample code that will take a raw xml byte stream and pretty print it. Here's some pseudo code showing one way that I might use this functionality: void my_write(const char* buf, int len); PrettyPrinter pp(bind(&my_write)); while (...) { // ... get some more xml ... const char* buf = xmlSource.get_buf(); int len = xmlSource.get_buf_len(); int written = pp.write(buf, len); // calls my_write with pretty printed xml // ... error handling, maybe call write again, etc. ... } I'd like to avoid instantiating a DOM representation. I already have dependencies on the expat and libxml2 shared libraries, and I'd rather not add any more shared library dependencies.

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• Where can I view rountrip information in my ASP.NET application?

  - by ajax81

  Hi All, I'm playing around with storing application settings in my database, but I think I may have created a situation where superfluous roundtrips are being made. Is there an easy way to view roundtrips made to an MS Access (I know, I know) backend? I guess while I'm here, I should ask for advice on the best way to handle this project. I'm building an app that generates links based on file names (files are numbered ints, 0-5000). The files are stored on network shares, arranged by name, and the paths change frequently as files are bulk transfered to create space, etc. Example: Files 1000 - 2000 go to /path/1000s Files 2001 - 3000 go to /path/2000s Files 3001 - 4000 go to /path/3000s etc I'm sure by now you can see where I'm going with this. Ultimately, I'm trying to avoid making a roundtrip to get the paths for every single file as they are displayed in a gridview. I'm open to the notion that I've gone about this all wrong and that my idea might be rubbish. I've toyed around with the notion of just creating a flat file, but if I do that, do I still run into the problem of having that file opened and closed for every file displayed in a gridview?

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• Creating android app Database with big amount of data

  - by Thomas

  Hi all, The database of my application need to be filled with a lot of data, so during onCreate(), it's not only some create table sql instructions, there is a lot of inserts. The solution I chose is to store all this instructions in a sql file located in res/raw and which is loaded with Resources.openRawResource(id). It works well but I face to encoding issue, I have some accentuated caharacters in the sql file which appears bad in my application. This my code to do this : public String getFileContent(Resources resources, int rawId) throws IOException { InputStream is = resources.openRawResource(rawId); int size = is.available(); // Read the entire asset into a local byte buffer. byte[] buffer = new byte[size]; is.read(buffer); is.close(); // Convert the buffer into a string. return new String(buffer); } public void onCreate(SQLiteDatabase db) { try { // get file content String sqlCode = getFileContent(mCtx.getResources(), R.raw.db_create); // execute code for (String sqlStatements : sqlCode.split(";")) { db.execSQL(sqlStatements); } Log.v("Creating database done."); } catch (IOException e) { // Should never happen! Log.e("Error reading sql file " + e.getMessage(), e); throw new RuntimeException(e); } catch (SQLException e) { Log.e("Error executing sql code " + e.getMessage(), e); throw new RuntimeException(e); } The solution I found to avoid this is to load the sql instructions from a huge static final string instead of a file, and all accentutated characters appears well. But Isn't there a more elegant way to load sql instructions than a big static final String attribute with all sql instructions ? Thanks in advance Thomas

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• Check a list of packages to install with apt-get

  - by Joel

  I am writing a post-install script for Ubuntu in Perl (same script as seen here). One of the steps is to install a list of packages. The problem is that if apt-get install fails in some of many different ways for any one of the packages the script dies badly. I would like to prevent that from happening. This happens because of the ways that apt-get install fails for packages that it doesn't like. For example when I try to install a nonsense word (i.e. typed in the wrong package name) $ sudo apt-get install oblihbyvl Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package oblihbyvl but if instead the package name has been obsoleted (installing handbrake from ppa) $ sudo apt-get install handbrake Reading package lists... Done Building dependency tree Reading state information... Done Package handbrake is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'handbrake' has no installation candidate $ apt-cache search handbrake handbrake-cli - versatile DVD ripper and video transcoder - command line handbrake-gtk - versatile DVD ripper and video transcoder - GTK GUI I have tried parsing the results of apt-cache and apt-get -s install to try to catch all possibilities before doing the install, but I seem to keep finding new ways to allow failures to continue to the actual install system command. My question is, is there some facility either in Perl (e.g. a module, though I would like to avoid installing modules if possible as this is supposed to be the first thing run after a new install of Ubuntu) or apt-* or dpkg that would let me be sure that the packages are all available to be installed before installing and if not fail gracefully in some way that lets the user decide what to do?

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• jquery form validation, and submit-on-change

  - by Bee

  I want to make all my settings forms across my site confirm that changes are saved, kinda like facebook does if you make changes in a form and then try to navigate away without saving. So I'm disabling the submit button on the forms only enabling if the values change. I then prompt the user to hit save before they leave the page in the case that they do have changes pending. var form = $('form.edit'); if(form.length > 0) { var orig_str = form.serialize(); $(':submit',form).attr('disabled','disabled'); form.on('change keyup', function(){ if(form.serialize() == orig_str) { setConfirmUnload(false); $(':submit',form).attr('disabled','disabled'); } else { setConfirmUnload(true); $(':submit',form).removeAttr('disabled') } }); $('input[type=submit]').click(function(){ setConfirmUnload(false); }); } function setConfirmUnload(on) { window.onbeforeunload = (on) ? unloadMessage : null; } function unloadMessage() { return 'If you navigate away from this page without saving your changes, they will be lost.'; } One of these forms needs some additional validation which I do using jQuery.validate library. e.g. if i wanted to ensure the user can't double submit the form on accident by double clicking on submit or somesuch (the actual validation in question is for a credit-card form and not this simple): $('form').validate({ submitHandler: function(form) { $(':submit', form).attr('disabled','disabled'); form.submit(); } }); Unfortunately both bits are trying to bind to submit button and they're interfering with each other such that the submit button remains disabled no matter what I do and it is impossible to submit the form at all. Is there some way to chain the validations together or something? Or some other way to avoid re-writing the validation code to repeat the "did you change anything in the form" business?

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• C++ variable to const expression

  - by user1344784

  template <typename Real> class A{ }; template <typename Real> class B{ }; //... a few dozen more similar template classes class Computer{ public slots: void setFrom(int from){ from_ = from; } void setTo(int to){ to_ = to; } private: template <int F, int T> void compute(){ using boost::fusion::vector; using boost::fusion::at_c; vector<A<float>, B<float>, ...> v; at_c<from_>(v).operator()(at_c<to_>(v)); //error; needs to be const-expression. }; This question isn't about Qt, but there is a line of Qt code in my example. The setFrom() and setTo() are functions that are called based on user selection via the GUI widget. The root of my problem is that 'from' and 'to' are variables. In my compute member function I need to pick a type (A, B, etc.) based on the values of 'from' and 'to'. The only way I know how to do what I need to do is to use switch statements, but that's extremely tedious in my case and I would like to avoid. Is there anyway to convert the error line to a constant-expression?

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• Proper API Design for Version Independence?

  - by Justavian

  I've inherited an enormous .NET solution of about 200 projects. There are now some developers who wish to start adding their own components into our application, which will require that we begin exposing functionality via an API. The major problem with that, of course, is that the solution we've got on our hands contains such a spider web of dependencies that we have to be careful to avoid sabotaging the API every time there's a minor change somewhere in the app. We'd also like to be able to incrementally expose new functionality without destroying any previous third party apps. I have a way to solve this problem, but i'm not sure it's the ideal way - i was looking for other ideas. My plan would be to essentially have three dlls. APIServer_1_0.dll - this would be the dll with all of the dependencies. APIClient_1_0.dll - this would be the dll our developers would actual refer to. No references to any of the mess in our solution. APISupport_1_0.dll - this would contain the interfaces which would allow the client piece to dynamically load the "server" component and perform whatever functions are required. Both of the above dlls would depend upon this. It would be the only dll that the "client" piece refers to. I initially arrived at this design, because the way in which we do inter process communication between windows services is sort of similar (except that the client talks to the server via named pipes, rather than dynamically loading dlls). While i'm fairly certain i can make this work, i'm curious to know if there are better ways to accomplish the same task.

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• Hibernate NamingStrategy implementation that maintains state between calls

  - by Robert Petermeier

  Hi, I'm working on a project where we use Hibernate and JBoss 5.1. We need our entity classes to be mapped to Oracle tables that follow a certain naming convention. I'd like to avoid having to specify each table and column name in annotations. Therefore, I'm currently considering implementing a custom implementation of org.hibernate.cfg.NamingStrategy. The SQL naming conventions require the name of columns to have a suffix that is equivalent to a prefix of the table name. If there is a table "T100_RESOURCE", the ID column would have to be named "RES_ID_T100". In order to implement this in a NamingStrategy, the implementation would have to maintain state, i.e. the current class name it is creating the mappings for. It would rely on Hibernate to always call classToTableName() before propertyToColumnName() and to determine all column names by calling propertyToColumnName() before the next call to classToTableName() Is it safe to do that or are there situations where Hibernate will mix things up? I am not thinking of problems through multiple threads here (which can be solved by keeping the last class name in a ThreadLocal) but also of Hibernate deliberately calling this out of order in certain circumstances. For example Hibernate asking for mappings of three properties of class A, then one of class B, then again more attributes of class A.

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• Why would using a Temp table be faster than a nested query?

  - by Mongus Pong

  We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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• MD5CryptoServiceProvider ComputeHash Issues between VS 2003 and VS 2008

  - by owensoroke

  I have a database application that generates a MD5 hash and compares the hash value to a value in our DB (SQL 2K). The original application was written in Visual Studio 2003 and a deployed version has been working for years. Recently, some new machines on the .NET framework 3.5 have been having unrelated issues with our runtime. This has forced us to port our code path from Visual Studio 2003 to Visual Studio 2008. Since that time the hash produced by the code is different than the values in the database. The original call to the function posted in code is: RemoveInvalidPasswordCharactersFromHashedPassword(Text_Scrub(GenerateMD5Hash(strPSW))) I am looking for expert guidance as to whether or not the MD5 methods have changed since VS 2K3 (causing this point of failure), or where other possible problems may be originating from. I realize this may not be the best method to hash, but utimately any changes to the MD5 code would force us to change some 300 values in our DB table and would cost us a lot of time. In addition, I am trying to avoid having to redeploy all of the functioning versions of this application. I am more than happy to post other code including the RemoveInvalidPasswordCharactersFromHashedPassword function, or our Text_Scrub if it is necessary to recieve appropriate feedback. Thank you in advance for your input. Public Function GenerateMD5Hash(ByVal strInput As String) As String Dim md5Provider As MD5 ' generate bytes for the input string Dim inputData() As Byte = ASCIIEncoding.ASCII.GetBytes(strInput) ' compute MD5 hash md5Provider = New MD5CryptoServiceProvider Dim hashResult() As Byte = md5Provider.ComputeHash(inputData) Return ASCIIEncoding.ASCII.GetString(hashResult) End Function

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• Unable to delete inherited entity class in EF4

  - by Coding Gorilla

  I have two entities in an EF4 model (using Model First), let's call them EntityA and EntityB. EntityA is marked as abstract, and EntityB inherits from EntityA. They are similar to the following: public class EntityA { public Guid Id; public string Name; public string Uri; } public class EntityB : EntityA { public string AnotherProperty; } The generated database tables look as I would expect them, with EntityA as on table, and then another table like: EntityA_EntityB Id (PK, FK, uniqueidentifier) AnotherProperty (varchar) There is a foreign key constraint on EntityA_EntityB that references EntityA's Id property, no cascades are configured (although I did try changing these myself). The problem is that when I attempt to do something like: Context.DeleteObject(EntityA_EntityB); EF attempts to delete the EntityA_EntityB table record before deleting the EntityA table record, which of course violates the foreign key constraint on EntityA_EntityB table. Using EFProfiler I see the following commands being sent to the database: delete [dbo].[EntityA_EntityB] where (([Id] = '5c02899f-09ea-2ed9-d44b-01aef80f6b64' /* @0 */) followed by delete [dbo].[EntityA] where ([Id] = '5c02899f-09ea-2ed9-d44b-01aef80f6b64' /* @0 */) I'm completely stumped as to how to get around this problem. I would think the EF should know that it needs to delete the base class first, before deleting the inherited class. I know I could do some triggers or other database type solutions, but I'd rather avoid doing that if I can. All my classes are POCO built using some customized T4 templates. I don't want to paste in a lot of extraneous code, but if you need more information I'll provide what I can.

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