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• Want to display a 3D model on the iPhone: how to get started?

  - by JeremyReimer

  I want to display and rotate a single 3D model, preferably textured, on the iPhone. Doesn't have to zoom in and out, or have a background, or anything. I have the following: an iPhone a MacBook the iPhone SDK Blender My knowledge base: I can make 3D models in various 3D programs (I'm most comfortable with 3D Studio Max, which I once took a course on, but I've used others) General knowledge of procedural programming from years ago (QuickBasic - I'm old!) Beginner's knowledge of object-oriented programming from going through simple Java and C# tutorials (Head Start C# book and my wife's intro to OOP course that used Java) I have managed to display a 3D textured model and spin it using a tutorial in C# I got off the net (I didn't just copy and paste, I understand basically how it works) and the XNA game development library, using Visual Studio on Windows. What I do not know: Much about Objective C Anything about OpenGL or OpenGL ES, which the iPhone apparently uses Anything about XCode My main problem is that I don't know where to start! All the iPhone books I found seem to be about creating GUI applications, not OpenGL apps. I found an OpenGL book but I don't know how much, if any, applies to iPhone development. And I find the Objective C syntax somewhat confusing, with the weird nested method naming, things like "id" that don't make sense, and the scary thought that I have to do manual memory management. Where is the best place to start? I couldn't find any tutorials for this sort of thing, but maybe my Google-Fu is weak. Or maybe I should start with learning Objective C? I know of books like Aaron Hillgrass', but I've also read that they are outdated and much of the sample code doesn't work on the iPhone SDK, plus it seems geared towards the Model-View-Controller paradigm which doesn't seem that suited for 3D apps. Basically I'm confused about what my first steps should be.

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• How do I debug into an ILMerged assembly?

  - by Rory Becker

  Summary I want to alter the build process of a 2-assembly solution, such that a call to ILMerge is invoked, and the build results in a single assembly. Further I would like to be able to debug into the resultant assembly. Preparation - A simple example New Solution - ClassLibrary1 Create a static function 'GetMessage' in Class1 which returns the string "Hello world" Create new console app which references the ClassLibrary. Output GetMessage from main() via the console. You now have a 2 assembly app which outputs "Hello World" to the console. So what next..? I would like to alter the Console app build process, to include a post build step which uses ILMerge, to merge the ClassLibrary assembly into the Console assembly After this step I should be able to: Run the Console app directly with no ClassLibrary1.dll present Run the Console app via F5 (or F11) in VS and be able to debug into each of the 2 projects. Limited Success I read this blogpost and managed to achieve the merge I was after with a post-build command of... "$(ProjectDir)ILMerge.bat" "$(TargetDir)" $(ProjectName) ...and an ILMerge.bat file which read... CD %1 Copy %2.exe temp.exe ILMerge.exe /out:%2.exe temp.exe ClassLibrary1.dll Del temp.exe Del ClassLibrary1.* This works fairly well, and does in fact produce an exe which runs outside the VS environment as required. However it does not appear to produce symbols (.pdb file) which VS is able to use in order to debug into the code. I think this is the last piece of the puzzle. Does anyone know how I can make this work? FWIW I am running VS2010 on an x64 Win7 x64 machine.

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• How to make HTML layout whitespace-agnostic?

  - by ssg

  If you have consecutive inline-blocks white-space becomes significant. It adds some level of space between elements. What's the "correct" way of avoiding whitespace effect to HTML layout if you want those blocks to look stuck to each other? Example: <span>a</span> <span>b</span> This renders differently than: <span>a</span><span>b</span> because of the space inbetween. I want whitespace-effect to go away without compromising HTML source code layout. I want my HTML templates to stay clean and well-indented. I think these options are ugly: 1) Tweaking text-indent, margin, padding etc. (Because it would be dependent on font-size, default white-space width etc) 2) Putting everything on a single line, next to each other. 3) Zero font-size. That would require overriding font-size in blocks, which would otherwise be inherited. 4) Possible document-wide solutions. I want the solution to stay local for a certain block of HTML. Any ideas, any obvious points which I'm missing?

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• Why do WCF clients depend on the app.config file?

  - by routeNpingme

  Like a lot of things, I'm sure there's a good reason for this, so please help me understand... Why, by default, do WCF services store settings in app.config? This has been so frustrating trying to work with multiple Silverlight class libraries. These class libraries are supposed to be completely independent from each other, and this dependency on the app.config seems to cause the following headaches: Single Responsibility Principle - I should be able to add a reference to a class library and go. If that class library uses a service reference, this idea is shot before I even start coding against it. Muddy Configuration - To get other libraries to work, I have to copy and paste the service configurations into the "main" application configs. If an endpoint changes in any way, I can't just worry about a new version of that class DLL - I have to worry about anything that uses it, too. Complex Alternatives - Programmatically creating the endpoint isn't pretty. Period. There has to be a better way. Why doesn't WCF at least separate the service configurations into a ServiceName.config or something that gets copied to an output directory. What am I missing? How do you deal with this?

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• How to display many SVGs in Java with high performance

  - by Oak

  What I want My goal is to be able to display a large number of SVG images on a single drawing area in Java, each with its own translation/rotation/scale values. I'm looking for the simplest solution allowing this, optionally even using OpenGL to speed things up. What I've Tried My initial naive approach was to use SVGSalamander to draw directly on a JPanel, but the performance was pathetic. I poked around around and learned that I should do something like manually convert each SVG into a BufferedImage created with createCompatibleImage, then do the transformations I want, then draw it using double buffering. I ran into some troubles here, and before I continued I tried looking for frameworks to simplify things. What I've Looked At I've been a bit overwhelmed by the available options, which is why I'm turning to SO for help. I've looked at: Cairo (with Glitz maybe?) Libart - not sure if this actually supports SVGs FengGUI Slick - looks promising but a bit of an overkill But couldn't decide what is best for me to start working with, and I hope someone here as experience with any of these doing similar things.

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• Jboss 6 Cluster Singleton Clustered

  - by DanC

  I am trying to set up a Jboss 6 in a clustered environment, and use it to host clustered stateful singleton EJBs. So far we succesfully installed a Singleton EJB within the cluster, where different entrypoints to our application (through a website deployed on each node) point to a single environment on which the EJB is hosted (thus mantaining the state of static variables). We achieved this using the following configuration: Bean interface: @Remote public interface IUniverse { ... } Bean implementation: @Clustered @Stateful public class Universe implements IUniverse { private static Vector<String> messages = new Vector<String>(); ... } jboss-beans.xml configuration: <deployment xmlns="urn:jboss:bean-deployer:2.0"> <!-- This bean is an example of a clustered singleton --> <bean name="Universe" class="Universe"> </bean> <bean name="UniverseController" class="org.jboss.ha.singleton.HASingletonController"> <property name="HAPartition"><inject bean="HAPartition"/></property> <property name="target"><inject bean="Universe"/></property> <property name="targetStartMethod">startSingleton</property> <property name="targetStopMethod">stopSingleton</property> </bean> </deployment> The main problem for this implementation is that, after the master node (the one that contains the state of the singleton EJB) shuts down gracefuly, the Singleton's state is lost and reset to default. Please note that everything was constructed following the JBoss 5 Clustering documents, as no JBoss 6 documents were found on this subject. Any information on how to solve this problem or where to find JBoss 6 documention on clustering is appreciated.

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• Loading an XML configuration file BEFORE the flex application loads

  - by Shahar

  Hi, We are using an XML file as an external configuration file for several parameters in our application (including default values for UI components and properties values of some service layer objects). The idea is to be able to load the XML configuration file before the flex application initializes any of its components. This is crucial because XML loading is processed a-synchronously in flex, which can potentially cause race-conditions in the application. For example: the configuration file holds the endpoint URL of a web service used to obtain data from the server. The URL resides in the XML because we want to allow our users to alter the endpoint URL according to their environment. Now because the endpoint URL is retrieved only after the XML has been completely loaded, some of the application's components might be invoking operations on this web service before it is initialized with the correct endpoint. The trivial solution would have been to suspend the initialization of the application until the complete event is dispatched by the loader. But it appears that this solution is far from being trivial. I haven't found a single solution that allows me to load the XML before any other object in the application. Can anyone advice or comment on this matter? Regards, Shahar

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• How to implement generic callbacks in C++

  - by Kylotan

  Forgive my ignorance in asking this basic question but I've become so used to using Python where this sort of thing is trivial that I've completely forgotten how I would attempt this in C++. I want to be able to pass a callback to a function that performs a slow process in the background, and have it called later when the process is complete. This callback could be a free function, a static function, or a member function. I'd also like to be able to inject some arbitrary arguments in there for context. (ie. Implementing a very poor man's coroutine, in a way.) On top of that, this function will always take a std::string, which is the output of the process. I don't mind if the position of this argument in the final callback parameter list is fixed. I get the feeling that the answer will involve boost::bind and boost::function but I can't work out the precise invocations that would be necessary in order to create arbitrary callables (while currying them to just take a single string), store them in the background process, and invoke the callable correctly with the string parameter.

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• Importing into a Exported object with MEF

  - by Nathan W

  I'm sorry if this question has already been asked 100 times, but I'm really struggling to get it to work. Say I have have three projects. Core.dll Has common interfaces Shell.exe Loads all modules in assembly folder. References Core.dll ModuleA.dll Exports Name, Version of module. References Core.dll Shell.exe has a [Export] that contains an single instance of a third party application that I need to inject into all loaded modules. So far the code that I have in Shell.exe is: static void Main(string[] args) { ThirdPartyApp map = new ThirdPartyApp(); var ad = new AssemblyCatalog(Assembly.GetExecutingAssembly()); var dircatalog = new DirectoryCatalog("."); var a = new AggregateCatalog(dircatalog, ad); // Not to sure what to do here. } class Test { [Export(typeof(ThirdPartyApp))] public ThirdPartyApp Instance { get; set; } [Import(typeof(IModule))] public IModule Module { get; set; } } I need to create a instance of Test, and load Instance with map from the Main method then load the Module from ModuleA.dll that is in the executing directory then [Import] Instance into the loaded module. In ModuleA I have a class like this: [Export(IModule)] class Module : IModule { [Import(ThirdPartyApp)] public ThirdPartyApp Instance {get;set;} } I know I'm half way there I just don't know how to put it all together, mainly with loading up test with a instance of map from Main. Could anyone help me with this.

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• creating matrix with probabilities

  - by John Chan

  Hi all, I want to generate a matrix of NxN to test some code that I have where each row contains floats as the elements and has to add up to 1 (i.e. a row with a set of probabilities). Where it gets tricky is that I want to make sure that randomly some of the elements should be 0 (in fact most of the elements should be 0 except for some random ones to be the probabilities). I need the probabilities to be 1/m where m is the number of elements that are not 0 within a single row. I tried to think of ways to output this, but essentially I would need this stored in a C++ array. So even if I output to a file I would still have the issue of not having it in array as I need it. At the end of it all I need that array because I want to generate a Market Matrix file. I found an implementation in C++ to take an array and convert it to the market matrix file, so this is what I am basing my findings on. My input for the rest of the code takes in this market matrix file so I need that to be the primary form of output. The language does not matter, I just want to generate the file at the end (I found a way mmwrite and mmread in python as well) Please help, I am stuck and not really sure how to implement this.

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• Component based web project directory layout with git and symlinks

  - by karlthorwald

  I am planning my directory structure for a linux/apache/php web project like this: Only www.example.com/webroot/ will be exposed in apache www.example.com/ webroot/ index.php comp1/ comp2/ component/ comp1/ comp1.class.php comp1.js comp2/ comp2.class.php comp2.css lib/ lib1/ lib1.class.php the component/ and lib/ directory will only be in the php path. To make the css and js files visible in the webroot directory I am planning to use symlinks. webroot/ index.php comp1/ comp1.js (symlinked) comp2/ comp2.css (symlinked) I tried following these principles: layout by components and libraries, not by file type and not by "public' or 'non public', index.php is an exception. This is for easier development. symlinking files that need to be public for the components and libs to a public location, but still mirroring the layout. So the component and library structure is also visible in the resulting html code in the links, which might help development. git usage should be safe and always work. it would be ok to follow some procedure to add a symlink to git, but after that checking them out or changing branches should be handled safely and clean How will git handle the symlinking of the single files correctly, is there something to consider? When it comes to images I will need to link directories, how to handle that with git? component/ comp3/ comp3.class.php img/ img1.jpg img2.jpg img3.jpg They should be linked here: webroot/ comp3/ img/ (symlinked ?) If using symlinks for that has disadvantages maybe I could move images to the webroot/ tree directly, which would break the first principle for the third (git practicability). So this is a git and symlink question. But I would be interested to hear comments about the php layout, maybe you want to use the comment function for this.

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• alternative to #include within namespace { } block

  - by Jeff

  Edit: I know that method 1 is essentially invalid and will probably use method 2, but I'm looking for the best hack or a better solution to mitigate rampant, mutable namespace proliferation. I have multiple class or method definitions in one namespace that have different dependencies, and would like to use the fewest namespace blocks or explicit scopings possible but while grouping #include directives with the definitions that require them as best as possible. I've never seen any indication that any preprocessor could be told to exclude namespace {} scoping from #include contents, but I'm here to ask if something similar to this is possible: (see bottom for explanation of why I want something dead simple) // NOTE: apple.h, etc., contents are *NOT* intended to be in namespace Foo! // would prefer something most this: namespace Foo { #include "apple.h" B *A::blah(B const *x) { /* ... */ } #include "banana.h" int B::whatever(C const &var) { /* ... */ } #include "blueberry.h" void B::something() { /* ... */ } } // namespace Foo ... // over this: #include "apple.h" #include "banana.h" #include "blueberry.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } int B::whatever(C const &var) { /* ... */ } void B::something() { /* ... */ } } // namespace Foo ... // or over this: #include "apple.h" namespace Foo { B *A::blah(B const *x) { /* ... */ } } // namespace Foo #include "banana.h" namespace Foo { int B::whatever(C const &var) { /* ... */ } } // namespace Foo #include "blueberry.h" namespace Foo { void B::something() { /* ... */ } } // namespace Foo My real problem is that I have projects where a module may need to be branched but have coexisting components from the branches in the same program. I have classes like FooA, etc., that I've called Foo::A in the hopes being able to branch less painfully as Foo::v1_2::A, where some program may need both a Foo::A and a Foo::v1_2::A. I'd like "Foo" or "Foo::v1_2" to show up only really once per file, as a single namespace block, if possible. Moreover, I tend to prefer to locate blocks of #include directives immediately above the first definition in the file that requires them. What's my best choice, or alternatively, what should I be doing instead of hijacking the namespaces?

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• functions with same names in javascript

  - by biju

  Hi, I tried to write a function on a js file and another function with the same name in the page.I expected an error but no error came and i got only the function from the js file to execute.How is this possible.Even if i write a function in a separate js file,everything is rendered in a single html file.Then how come it is possible <script type="text/javascript" language="javascript" src="JScript.js" /> <script language="javascript"> function Boo() { alert("Hai new"); } </script> <head runat="server"> <title></title> </head> <body> <form id="form1" runat="server"> <div> <asp:Button runat=server OnClientClick="Boo();" Text="Click" /> </div> </form> </body> and in the js file function Boo() { alert("Hai"); }

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• .NET Regex - Replace multiple characters at once without overwriting?

  - by Everaldo Aguiar

  I'm implementing a c# program that should automatize a Mono-alphabetic substitution cipher. The functionality i'm working on at the moment is the simplest one: The user will provide a plain text and a cipher alphabet, for example: Plain text(input): THIS IS A TEST Cipher alphabet: A - Y, H - Z, I - K, S - L, E - J, T - Q Cipher Text(output): QZKL KL QJLQ I thought of using regular expressions since I've been programming in perl for a while, but I'm encountering some problems on c#. First I would like to know if someone would have a suggestion for a regular expression that would replace all occurrence of each letter by its corresponding cipher letter (provided by user) at once and without overwriting anything. Example: In this case, user provides plaintext "TEST", and on his cipher alphabet, he wishes to have all his T's replaced with E's, E's replaced with Y and S replaced with J. My first thought was to substitute each occurrence of a letter with an individual character and then replace that character by the cipherletter corresponding to the plaintext letter provided. Using the same example word "TEST", the steps taken by the program to provide an answer would be: 1 - replace T's with (lets say) @ 2 - replace E's with # 3 - replace S's with & 4 - Replace @ with E, # with Y, & with j 5 - Output = EYJE This solution doesn't seem to work for large texts. I would like to know if anyone can think of a single regular expression that would allow me to replace each letter in a given text by its corresponding letter in a 26-letter cipher alphabet without the need of splitting the task in an intermediate step as I mentioned. If it helps visualize the process, this is a print screen of my GUI for the program:

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• IIS URL Rewrite rule - Default document for subdirectories

  - by Antonio Bakula

  I would like create URL rewrite rule that will set default document for my virtual folders. eg. someting like this www.domain.com/en/ -> www.domain.com/en/index.aspx www.domain.com/hr/ -> www.domain.com/hr/index.aspx www.domain.com/de/ -> www.domain.com/de/index.aspx directories en, hr, de doesn't really exists on web server they are just markers for languange used in site used by home grown http module that will rewrite path with query params. Quick solution was define rule for every single lang, something like this : <rewrite> <rewriteMaps> <rewriteMap name="Langs"> <add key="/en" value="/en/index.aspx" /> <add key="/hr" value="/hr/index.aspx" /> <add key="/de" value="/de/index.aspx" /> </rewriteMap> </rewriteMaps> <rules> But I would really like solution that would not require changes in web.config and adding rewrite rule for every languange used on particular site. Thanks !

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• Selenium Webdriver Java - looking for alternatives for Actions and Robot when performing drag-and-drop

  - by Ja-ke Alconcel

  I first tried Actions class and the drag-and-drop does work on different elements, however it was unable to locate the a specific draggable element on it's exact screen/webpage position. Here's the code I've used: Point loc = driver.findElement(By.id("thiselement")).getLocation(); System.out.println(loc); WebElement drag = driver.findElement(By.id("thiselement")); Actions test = new Actions(driver); test.dragAndDropBy(drag, 0, 60).build().perform(); I checked the element with it's pixel location and it prints (837, -52), which was somewhere on top of the webpage and was pixels away from the actual element. Then I tried using the Robot class and works perfectly fine on my script, but can only provide constant successful runs on a single test machine, running it with a different machine with different screen resolution and screen size will render the script to fail due to the dependency of Robot on the pixel location of the element. The sample code of the Robot script I'm using: Robot dragAndDrop = new Robot(); dragAndDrop.mouseMove(945, 166); //actual pixel location of the draggable element dragAndDrop.mousePress(InputEvent.BUTTON1_MASK); sleep(3000); dragAndDrop.mouseMove(945, 226); dragAndDrop.mouseRelease(InputEvent.BUTTON1_MASK); sleep(3000); Is there any alternative for Actions and Robot to automate drag-and-drop? Or maybe a help on working the script to work on Actions as I really can't use Robot. Thanks in advance.

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• Group / User based security. Table / SQL question

  - by Brett

  Hi, I'm setting up a group / user based security system. I have 4 tables as follows: user groups group_user_mappings acl where acl is the mapping between an item_id and either a group or a user. The way I've done the acl table, I have 3 columns of note (actually 4th one as an auto-id, but that is irrelevant) col 1 item_id (item to access) col 3 user_id (user that is allowed to access) col 3 group_id (group that is allowed to access) So for example item1, peter, , item2, , group1 item3, jane, , so either the acl will give access to a user or a group. Any one line in the ACL table with either have an item - user mapping, or an item group. If I want to have a query that returns all objects a user has access to, I think I need to have a SQL query with a UNION, because I need 2 separate queries that join like.. item - acl - group - user AND item - acl - user This I guess will work OK. Is this how its normally done? Am I doing this the right way? Seems a little messy. I was thinking I could get around it by creating a single user group for each person, so I only ever deal with groups in my SQL, but this seems a little messy as well..

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• Generate and download a text file in javascript

  - by Mark B

  All my research so far suggests this can't be done, but I'm hoping someone here has some cunning ideas. I have a form on a website which allows users to bulk upload lots of URLs to add to a list on the server. There's quite a lot of server-side processing to do on each URL, so to avoid timeouts and to display progress, I've implemented the upload using jQuery to submit the URLs one at a time using ajax. This is all working nicely. However, part of the processing on each URL is deduplicating it against the complete list. The ajax call returns a status indicating either a successful upload or a rejection due to duplication. As the upload progresses, I tell the user how many URLs have been rejected as duplicates (along with overall progress and ETA). The problem now is how to give the user a complete list of the failed duplicate URLs. I've kept them in an array in my jQuery, and would like the user to be able to click on a link on the form to download a text file containing those URLs. Is this possible just using client-side processing? The server-side processing basically handles a single keyword at a time. I'd rather not have to store the duplicates in a database table with some kind of session key which gets sent with every ajax call, and is then used at the end to generate the text file server-side (and then gets cleaned up some time later). I can see how to do this, but it seems very clunky and a bit 20th century.

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• How to exclude rows where matching join is in an SQL tree

  - by Greg K

  Sorry for the poor title, I couldn't think how to concisely describe this problem. I have a set of items that should have a 1-to-1 relationship with an attribute. I have a query to return those rows where the data is wrong and this relationship has been broken (1-to-many). I'm gathering these rows to fix them and restore this 1-to-1 relationship. This is a theoretical simplification of my actual problem but I'll post example table schema here as it was requested. item table: +------------+------------+-----------+ | item_id | name | attr_id | +------------+------------+-----------+ | 1 | BMW 320d | 20 | | 1 | BMW 320d | 21 | | 2 | BMW 335i | 23 | | 2 | BMW 335i | 34 | +------------+------------+-----------+ attribute table: +---------+-----------------+------------+ | attr_id | value | parent_id | +---------+-----------------+------------+ | 20 | SE | 21 | | 21 | M Sport | 0 | | 23 | AC | 24 | | 24 | Climate control | 0 | .... | 34 | Leather seats | 0 | +---------+-----------------+------------+ A simple query to return items with more than one attribute. SELECT item_id, COUNT(DISTINCT(attr_id)) AS attributes FROM item GROUP BY item_id HAVING attributes > 1 This gets me a result set like so: +-----------+------------+ | item_id | attributes | +-----------+------------+ | 1 | 2 | | 2 | 2 | | 3 | 2 | -- etc. -- However, there's an exception. The attribute table can hold a tree structure, via parent links in the table. For certain rows, parent_id can hold the ID of another attribute. There's only one level to this tree. Example: +---------+-----------------+------------+ | attr_id | value | parent_id | +---------+-----------------+------------+ | 20 | SE | 21 | | 21 | M Sport | 0 | .... I do not want to retrieve items in my original query where, for a pair of associated attributes, they related like attributes 20 & 21. I do want to retrieve items where: the attributes have no parent for two or more attributes they are not related (e.g. attributes 23 & 34) Example result desired, just the item ID: +------------+ | item_id | +------------+ | 2 | +------------+ How can I join against attributes from items and exclude these rows? Do I use a temporary table or can I achieve this from a single query? Thanks.

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• Should methods that are required to be executed in a specific order be private?

  - by TooFat

  I have a Class that retrieves some data and images does some stuff to them and them uploads them to a third party app using web services. The object needs to perform some specific steps in order. My question is should I be explicitly exposing each method publicly like so. myObject obj = new myObject(); obj.RetrieveImages(); obj.RetrieveAssociatedData(); obj.LogIntoThirdPartyWebService(); obj.UploadStuffToWebService(); or should all of these methods be private and encapsulated in a single public method like so. public class myObject() { private void RetrieveImages(){}; private void RetrieveAssociatedData(){}; private void LogIntoThirdPartyWebService(){}; private void UploadStuffToWebService(){}; public void DoStuff() { this.RetrieveImages(); this.RetrieveAssociatedData(); this.LogIntoThirdPartyWebService(); this.UploadStuffToWebService(); } } which is called like so. myObject obj = new myObject(); obj.DoStuff();

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• New record may be written twice in clusterd index structure

  - by Cupidvogel

  As per the article at Microsoft, under the Test 1: INSERT Performance section, it is written that For the table with the clustered index, only a single write operation is required since the leaf nodes of the clustered index are data pages (as explained in the section Clustered Indexes and Heaps), whereas for the table with the nonclustered index, two write operations are required—one for the entry into the index B-tree and another for the insert of the data itself. I don't think that is necessarily true. Clustered Indexes are implemented through B+ tree structures, right? If you look at at this article, which gives a simple example of inserting into a B+ tree, we can see that when 8 is initially inserted, it is written only once, but then when 5 comes in, it is written to the root node as well (thus written twice, albeit not initially at the time of insertion). Also when 8 comes in next, it is written twice, once at the root and then at the leaf. So won't it be correct to say, that the number of rewrites in case of a clustered index is much less compared to a NIC structure (where it must occur every time), instead of saying that rewrite doesn't occur in CI at all?

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• Does QThread::sleep() require the event loop to be running?

  - by suszterpatt

  I have a simple client-server program written in Qt, where processes communicate using MPI. The basic design I'm trying to implement is the following: The first process (the "server") launches a GUI (derived from QMainWindow), which listens for messages from the clients (using repeat fire QTimers and asynchronous MPI receive calls), updates the GUI depending on what messages it receives, and sends a reply to every message. Every other process (the "clients") runs in an infinite loop, and all they are intended to do is send a message to the server process, receive the reply, go to sleep for a while, then wake up and repeat. Every process instantiates a single object derived from QThread, and calls its start() method. The run() method of these classes all look like this: from foo.cpp: void Foo::run() { while (true) { // Send message to the first process // Wait for a reply // Do uninteresting stuff with the reply sleep(3); // also tried QThread::sleep(3) } } In the client's code, there is no call to exec() anywhere, so no event loop should start. The problem is that the clients never wake up from sleeping (if I surround the sleep() call with two writes to a log file, only the first one is executed, control never reaches the second). Is this because I didn't start the event loop? And if so, what is the simplest way to achieve the desired functionality?

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• JDBC transaction dead-lock solution required?

  - by user49767

  It's a scenario described my friend and challenged to find solution. He is using Oracle database and JDBC connection with read committed as transaction isolation level. In one of the transaction, he updates a record and executes selects statement and commits the transaction. when everything happening within single thread, things are fine. But when multiple requests are handled, dead-lock happens. Thread-A updates a record. Thread B updates another record. Thread-A issues select statement and waits for Thread-B's transaction to complete the commit operation. Thread-B issues select statement and waits for Thread-A's transaction to complete the commit operation. Now above causes dead-lock. Since they use command pattern, the base framework allows to issue commit only once (at the end of all the db operation), so they are unable to issue commit immediately after select statement. My argument was Thread-A supposed to select all the records which are committed and hence should not be issue. But he said that Thread-A will surely wait till Thread-B commits the record. is that true? What are all the ways, to avoid the above issue? is it possible to change isolation-level? (without changing underlying java framework) Little information about base framework, it is something similar to Struts action, their each and every request handled by one action, transaction begins before execution and commits after execution.

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• What's the next steps for moving from appengine to full django?

  - by tomcritchlow

  Hey guys, I'm super new to programming and I've been using appengine to help me learn python and general coding. I'm getting better quickly and I'm loving it all the way :) Appengine was awesome for allowing me to just dive into writing my app and getting something live that works (see http://www.7bks.com/). But I'm realising that the longer I continue to learn on appengine the more I'm constraining myself and locking myself into a single system. I'd like to move to developing on full django (since django looks super cool!). What are my next steps? To give you a feel for my level of knowledge: I'm not a unix user I'm not familiar with command line controls (I still use appengine/python completely via the appengine SDK) I've never programmed in anything other than python, anywhere other than appengine I know the word SQL, but don't know what MySQL is really or how to use it. So, specifically: What are the skills I need to learn to get up and running with full django/python? If I'm going to host somewhere else I suppose I'll need to learn some sysadmin type skills (maybe even unix?). Is there anywhere that offers easy hosting (like appengine) but that supports django? I hear such great things about heroku I'm considering switching to RoR and going there I appreciate that I'm likely not quite ready to move away from appengine just yet but I'm a fiercely passionate learner (http://www.7bks.com/blog/179001) and would love it if I knew all the steps I needed to learn so I could set about learning them. At the moment, I don't even know what the steps are I need to learn! Thank you very much. Sorry this isn't a specific programming question but I've looked around and haven't found a good how-to for someone of my level of experience and I think others would appreciate a good roadmap for the things we need to learn to get up and running. Thanks, Tom PS - if anyone is in London and fancies showing me the ropes in person that would be super awesome :)

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• Help me clean up this crazy lambda with the out keyword

  - by Sarah Vessels

  My code looks ugly, and I know there's got to be a better way of doing what I'm doing: private delegate string doStuff( PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt ); private bool tryEncryptPassword( doStuff encryptPassword, out string errorMessage ) { ...get some variables... string encryptedPassword = encryptPassword(encrypter, publicKey, privateKey, out salt); ... } This stuff so far doesn't bother me. It's how I'm calling tryEncryptPassword that looks so ugly, and has duplication because I call it from two methods: public bool method1(out string errorMessage) { string rawPassword = "foo"; return tryEncryptPassword( (PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt) => encrypter.EncryptPasswordAndDoStuff( // Overload 1 rawPassword, publicKey, privateKey, out salt ), out errorMessage ); } public bool method2(SecureString unencryptedPassword, out string errorMessage) { return tryEncryptPassword( (PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt) => encrypter.EncryptPasswordAndDoStuff( // Overload 2 unencryptedPassword, publicKey, privateKey, out salt ), out errorMessage ); } Two parts to the ugliness: I have to explicitly list all the parameter types in the lambda expression because of the single out parameter. The two overloads of EncryptPasswordAndDoStuff take all the same parameters except for the first parameter, which can either be a string or a SecureString. So method1 and method2 are pretty much identical, they just call different overloads of EncryptPasswordAndDoStuff. Any suggestions? Edit: if I apply Jeff's suggestions, I do the following call in method1: return tryEncryptPassword( (encrypter, publicKey, privateKey) => { var result = new EncryptionResult(); string salt; result.EncryptedValue = encrypter.EncryptPasswordAndDoStuff( rawPassword, publicKey, privateKey, out salt ); result.Salt = salt; return result; }, out errorMessage ); Much the same call is made in method2, just with a different first value to EncryptPasswordAndDoStuff. This is an improvement, but it still seems like a lot of duplicated code.

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