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• Async & Await in C# with Xamarin

  - by Wallym

   One of the great things about the .NET Framework is that Microsoft has worked long and hard to improve many features. Since the initial release of .NET 1.0, there has been support for threading via .NET threads as well as an application-level threadpool. This provided a great starting point when compared to Visual Basic 6 and classic ASP programming. The release of.NET 4 brought significant improvements in the area of threading, asynchronous operations and parallel operations. While the improvements made working with asynchronous operations easier, new problems were introduced, since many of these operations work based on callbacks. For example: How should a developer handle error checking? The program flow tends to be non-linear. Fixing bugs can be problematic. It is hard for a developer to get an understanding of what is happening within an application. The release of .NET 4.5 (and C# 5.0), in the fall of 2012, was a blockbuster update with regards to asynchronous operations and threads. Microsoft has added C# language keywords to take this non-linear callback-based program flow and turn it into a much more linear flow. Recently, Xamarin has updated Xamarin.Android and Xamarin.iOS to support async. This article will look at how Xamarin has implemented the .NET 4.5/C# 5 support into their Xamarin.iOS and Xamarin.Android productions. There are three general areas that I'll focus on: A general look at the asynchronous support in Xamarin's mobile products. This includes async, await, and the implications that this has for cross-platform code. The new HttpClient class that is provided in .NET 4.5/Mono 3.2. Xamarin's extensions for asynchronous operations for Android and iOS. FYI: Be aware that sometimes the OpenWeatherMap API breaks, for no reason.  I found this out after I shipped the article in.

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• Organizing an entity system with external component managers?

  - by Gustav

  I'm designing a game engine for a top-down multiplayer 2D shooter game, which I want to be reasonably reuseable for other top-down shooter games. At the moment I'm thinking about how something like an entity system in it should be designed. First I thought about this: I have a class called EntityManager. It should implement a method called Update and another one called Draw. The reason for me separating Logic and Rendering is because then I can omit the Draw method if running a standalone server. EntityManager owns a list of objects of type BaseEntity. Each entity owns a list of components such as EntityModel (the drawable representation of an entity), EntityNetworkInterface, and EntityPhysicalBody. EntityManager also owns a list of component managers like EntityRenderManager, EntityNetworkManager and EntityPhysicsManager. Each component manager keeps references to the entity components. There are various reasons for moving this code out of the entity's own class and do it collectively instead. For example, I'm using an external physics library, Box2D, for the game. In Box2D, you first add the bodies and shapes to a world (owned by the EntityPhysicsManager in this case) and add collision callbacks (which would be dispatched to the entity object itself in my system). Then you run a function which simulates everything in the system. I find it hard to find a better solution to do this than doing it in an external component manager like this. Entity creation is done like this: EntityManager implements the method RegisterEntity(entityClass, factory) which registers how to create an entity if that class. It also implements the method CreateEntity(entityClass) which would return an object of type BaseEntity. Well now comes my problem: How would the reference to a component be registered to the component managers? I have no idea how I would reference the component managers from a factory/closure.

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• What language should I use for making a cross platform library?

  - by Andrei

  I want to build a SyncML parsing library (no UI) which should be able to build up messages based on information provided by the host application, fed in by the library's methods. Also, the library should to be able to do callbacks to methods in the host application. I want to be able to compile this and have it available on as many platforms as possible: Windows, Windows Phone 7 OS, OSX, iOS, Linux, Android, BlackBerry. Basically as many platforms as possible. The priority is to have this available on mobile devices. Questions: What setup should I use? (programming languages, compilers, IDE etc.) How would I compile this library for these different platforms and how would I connect to it? Any other info? e.g. articles that cover the subject of cross-platform development? I haven't done this sort of a cross-platform project before, so any available information to put me in the right direction would be welcomed. Myself, I have a background in C#/.NET and Objective-C.

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• Keyboard input system handling

  - by The Communist Duck

  Note: I have to poll, rather than do callbacks because of API limitations (SFML). I also apologize for the lack of a 'decent' title. I think I have two questions here; how to register the input I'm receiving, and what to do with it. Handling Input I'm talking about after the fact you've registered that the 'A' key has been pressed, for example, and how to do it from there. I've seen an array of the whole keyboard, something like: bool keyboard[256]; //And each input loop check the state of every key on the keyboard But this seems inefficient. Not only are you coupling the key 'A' to 'player moving left', for example, but it checks every key, 30-60 times a second. I then tried another system which just looked for keys it wanted. std::map< unsigned char, Key keyMap; //Key stores the keycode, and whether it's been pressed. Then, I declare a load of const unsigned char called 'Quit' or 'PlayerLeft'. input-BindKey(Keys::PlayerLeft, KeyCode::A); //so now you can check if PlayerLeft, rather than if A. However, the problem with this is I cannot now type a name, for example, without having to bind every single key. Then, I have the second problem, which I cannot really think of a good solution for: Sending Input I now know that the A key has been pressed or that playerLeft is true. But how do I go from here? I thought about just checking if(input-IsKeyDown(Key::PlayerLeft) { player.MoveLeft(); } This couples the input greatly to the entities, and I find it rather messy. I'd prefer the player to handle its own movement when it gets updated. I thought some kind of event system could work, but I do not know how to go with it. (I heard signals and slots was good for this kind of work, but it's apparently very slow and I cannot see how it'd fit). Thanks.

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• Rails/Node.js interaction

  - by lpvn

  I and my co-worker are developing a web application with rails and node.js and we can't reach a consensus regarding a particular architectural decision. Our setup is basically a rails server working with node.js and redis, when a client makes a http request to our rails API in some cases our rails application posts the response to a redis database and then node.js transmits the response via websocket. Our disagreement occurs in the following point: my co-worker thinks that using node.js to send data to clients is somewhat business logic and should be inside the model, so in the first code he wrote he used commands of broadcast in callbacks and other places of the model, he's convinced that the models are the best place for the interaction between rails and node. I on the other hand think that using node.js belongs to the runtime realm, my take is that the broadcast commands and other node.js interactions should be in the controller and should only be used in a model if passed through a well defined interface, just like the situation when a model needs to access the current user of a session. At this point we're tired of arguing over this same thing and our discussion consists in us repeating to ourselves our same opinions over and over. Could anyone, preferably with experience in the same setup, give us an unambiguous response saying which solution is more adequate and why it is?

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• Collaboration using github and testing the code

  - by wyred

  The procedure in my team is that we all commit our code to the same development branch. We have a test server that runs updated code from this branch so that we can test our code on the servers. The problem is that if we want to merge the development branch to the master branch in order to publish new features to our production servers, some features that may not have been ready will be applied to the production servers. So we're considering having each developer work on a feature/topic branch where each of them work on their own features and when it's ready, merge it into the development branch for testing, and then into the master branch. However, because our test server only pulls changes from the development branch, the developers are unable to test their features. While this is not a huge issue as they can test it on their local machine, the only problem I foresee is if we want to test callbacks from third-party services like sendgrid (where you specify a url for sendgrid to update you on the status of emails sent out). How to handle this problem? Note: We're not advanced git users. We use the Github app for MacOSX and Windows to commit our work.

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• Did 12.04 just add multi-touch gesture support mid-release?

  - by adempewolff

  I was reviewing the updates I was about to download today and I noticed that a lot of them had to do with gesture support, noticed that many of these were new installs rather than upgrades. Has 12.04 just added multi-touch gesture support mid-release? If so, what are the capabilities that this adds? Which applications already support these capabilities and can I expect others to add support in the near future? Here are the packages that were installed: Install: libframe6:amd64 (2.2.4-0ubuntu0.12.04.1), libgeis1:amd64 (2.2.9.2-0ubuntu1), libgrail5:amd64 (3.0.6-0ubuntu0.12.04.01, automatic) And here are those that were upgraded (also including many with touch support): Upgrade: libgrip0:amd64 (0.3.4-0ubuntu2~ubuntu12.04.1, 0.3.5-0ubuntu1~12.04.1), eog:amd64 (3.4.2-0ubuntu1, 3.4.2-0ubuntu1.1), ginn:amd64 (0.2.4-0ubuntu1, 0.2.4.1-0ubuntu1) Of which the descriptions for the new installs are, libgeis1: Gesture engine interface support A common API for clients of a systemwide gesture recognition and propagation engine. libframe6: Touch Frame Library This library handles the buildup and synchronization of a set of simultaneous touches. The library is input agnostic, with bindings for mtdev, frame and XI2.1. libgrail5: Gesture Recognition And Instantiation Library This library consists of an interface and tools for handling gesture recognition and gesture instantiation. Applications can use the grail callbacks to receive gesture primitives and raw input events from the underlying kernel device. And the descriptions for the upgraded packages are, ligrip0: provides multitouch gestures to GTK+ apps Libgrip hooks gesture recognition into GTK+ applications. ginn: Gesture Injector: No-GEIS, No-Toolkits A daemon with jinn-like wish-granting capabilities: it gives applications the ability to support a subset of multi-touch gestures without having to integrate GEIS or multi-touch GTK/Qt libs. Adding in a ton of new libraries and upgrading the existing components makes me wonder if 12.04 is meant to start natively supporting gestures other than two finger scroll in the near future. I expected these capabilities to be introduced soon but I thought that they would only be rolled out in a new release, not as upgrades for an existing release. Anyone have any info about this?

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• Which approach would lead to an API that is easier to use?

  - by Clem

  I'm writing a JavaScript API and for a particular case, I'm wondering which approach is the sexiest. Let's take an example: writing a VideoPlayer, I add a getCurrentTime method which gives the elapsed time since the start. The first approach simply declares getCurrentTime as follows: getCurrentTime():number where number is the native number type. This approach includes a CURRENT_TIME_CHANGED event so that API users can add callbacks to be aware of time changes. Listening to this event would look like the following: myVideoPlayer.addEventListener(CURRENT_TIME_CHANGED, function(evt){ console.log ("current time = "+evt.getDispatcher().getCurrentTime()); }); The second approach declares getCurrentTime differently: getCurrentTime():CustomNumber where CustomNumber is a custom number object, not the native one. This custom object dispatches a VALUE_CHANGED event when its value changes, so there is no need for the CURRENT_TIME_CHANGED event! Just listen to the returned object for value changes! Listening to this event would look like the following: myVideoPlayer.getCurrentTime().addEventListener(VALUE_CHANGED, function(evt){ console.log ("current time = "+evt.getDispatcher().valueOf()); }); Note that CustomNumber has a valueOf method which returns a native number that lets the returned CustomNumber object being used as a number, so: var result = myVideoPlayer.getCurrentTime()+5; will work! So in the first approach, we listen to an object for a change in its property's value. In the second one we directly listen to the property for a change on its value. There are multiple pros and cons for each approach, I just want to know which one the developers would prefer to use!

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• Any Practical Alternative to the Signals + Slots model for GUI Programming?

  - by IntermediateHacker

  The majority of GUI Toolkits nowadays use the Signals + Slots model. It was Qt and GTK+, if I am not wrong, who pioneered it. You know, the widgets or graphical objects (sometimes even ones that aren't displayed) send signals to the main-loop handler. The main-loop handler then calls the events, callbacks or slots assigned for that widget / graphical object. There are usually default (and in most cases virtual) event-handlers already provided by the toolkit for handling all pre-defined signals, therefore, unlike previous designs where the developer had to write the entire main-loop and handler for each and every message himself (think WINAPI), the developer only has to worry about the signals he needs to implement new functionality on. Now this design is being used in most modern toolkits as far as I know. There are Qt, GTK+, FLTK etc. There is Java Swing. C# even has a language feature for it ( events and delegates ), and Windows Forms has been developed on this design. In fact, over the last decade, this design for GUI programming has become a kind of an unwritten standard. Since it increases productivity and provides greater abstraction. However, my question is: Is there any alternative design, that is parallel or practical for modern GUI programming? i.e Is the Signals + Slots design, the only practical one in town? Is it feasible to do GUI Programming with any other design? Are any modern (preferably successful and popular) GUI toolkits built on an alternative design?

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• 10.10 boots to command line login prompt

  - by greggory.hz

  I recently installed Ubuntu 10.10 on a computer that was previously running 10.04 (that worked fine). Now, each time I boot up, it starts up in a command line login prompt. I can login and it stays at the command line (as expected). I can then manually start gdm with sudo start gdm and it works fine. I can also enable compiz (using proprietary nvidia drivers) so I'm reasonably confident that it's not a driver problem (at least not in the sense that the drivers just flat out aren't working). Interestingly, if I leave it at the command prompt without logging in, after about 5 or 10 minutes, gnome starts up on its own. I'm not sure what is causing this. This is what dmesg | tail gives me after a manual start of gdm: [ 15.664166] NVRM: loading NVIDIA UNIX x86_64 Kernel Module 270.18 Tue Jan 18 21:46:26 PST 2011 [ 15.991304] type=1400 audit(1297543976.953:11): apparmor="STATUS" operation="profile_load" name="/usr/share/gdm/guest-session/Xsession" pid=990 comm="apparmor_parser" [ 16.606986] eth0: link up, 100Mbps, full-duplex, lpa 0xCDE1 [ 18.798506] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro,commit=0 [ 26.740010] eth0: no IPv6 routers present [ 90.444593] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro,commit=0 [ 189.252208] audit_printk_skb: 21 callbacks suppressed [ 189.252213] type=1400 audit(1297544150.218:19): apparmor="STATUS" operation="profile_replace" name="/usr/lib/cups/backend/cups-pdf" pid=1876 comm="apparmor_parser" [ 189.252584] type=1400 audit(1297544150.218:20): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/cupsd" pid=1876 comm="apparmor_parser" [ 351.159585] lo: Disabled Privacy Extensions

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• How to manage long running background threads and report progress with DDD

  - by Mr Happy

  Title says most of it. I have found surprising little information about this. I have a long running operation of which the user wants to see the progress (as in, item x of y processed). I also need to be able to pause and stop the operation. (Stopping doesn't rollback the items already processed.) The thing is, it's not that each item takes a long time to get processed, it's that that there are usually a lot of items. And what I've read about so far is that it's somewhat of an anti-pattern to put something like a queue in the DB. I currently don't have any messaging system in place, and I've never worked with one either. Another thing I read somewhere is that progress reporting is something that belongs in the application layer, but it didn't go into the details. So having said all this, what I have in mind is the following. User request with list of items enters the application layer. Application layer gets some information from the domain needed to process the items. Application layer passes the items and the information off to some domain service (should the implementation of this service belong in the infrastructure layer?) This service spins up a worker thread with callbacks for both progress reporting and pausing/stopping it. This worker thread will process each item in it's own UoW. This means the domain information from earlier needs to be stored in some DTO. Since nothing is really persisted, the service should be singleton and thread safe Whenever a user requests a progress report or wants to pause/stop the operation, the application layer will ask the service. Would this be a correct solution? Or am I at least on the right track with this? Especially the singleton and thread safe part makes the whole thing feel icky.

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• Is there a way to use the facebook sdk with libgdx?

  - by Rudy_TM

  I have tried to use the facebook sdk in libgdx with callbacks, but it never enters the authetication listeners, so the user never is logged in, it permits the authorization for the facebook app but it never implements the authentication interfaces :( Is there a way to use it? public MyFbClass() { facebook = new Facebook(APPID); mAsyncRunner = new AsyncFacebookRunner(facebook); SessionStore.restore(facebook, this); FB.init(this, 0, facebook, this.permissions); } ///Method for init the permissions and my listener for authetication public void init(final Activity activity, final Facebook fb,final String[] permissions) { mActivity = activity; this.fb = fb; mPermissions = permissions; mHandler = new Handler(); async = new AsyncFacebookRunner(mFb); params = new Bundle(); SessionEvents.addAuthListener(auth); } ///I call the authetication process, I call it with a callback from libgdx public void facebookAction() { // TODO Auto-generated method stub fb.authenticate(); } ///It only allow the app permission, it doesnt register the events public void authenticate() { if (mFb.isSessionValid()) { SessionEvents.onLogoutBegin(); AsyncFacebookRunner asyncRunner = new AsyncFacebookRunner(mFb); asyncRunner.logout(getContext(), new LogoutRequestListener()); //SessionStore.save(this.mFb, getContext()); } else { mFb.authorize(mActivity, mPermissions,0 , new DialogListener()); } } public class SessionListener implements AuthListener, LogoutListener { @Override public void onAuthSucceed() { SessionStore.save(mFb, getContext()); } @Override public void onAuthFail(String error) { } @Override public void onLogoutBegin() { } @Override public void onLogoutFinish() { SessionStore.clear(getContext()); } } DialogListener() { @Override public void onComplete(Bundle values) { SessionEvents.onLoginSuccess(); } @Override public void onFacebookError(FacebookError error) { SessionEvents.onLoginError(error.getMessage()); } @Override public void onError(DialogError error) { SessionEvents.onLoginError(error.getMessage()); } @Override public void onCancel() { SessionEvents.onLoginError("Action Canceled"); } }

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• Switching PHP to FastCGI from mod_php broke AMFPHP

  - by wezzy

  Hi, i've just switched my debian server from mod_php to fastcgi following this tutorial everything goes right but now i've found that one of the hosted application that using AMFPHP for flash remoting is broken. I'm trying to understand what's happend. Looking at it with FireBug and FireAMF it seems that the responses has a content but the Flash callbacks never get called and if i try to open the service browser it displays this error: (mx.rpc::Fault)#0 errorID = 0 faultCode = "Client.Error.RequestTimeout" faultDetail = "The request timeout for the sent message was reached without receiving a response from the server." faultString = "Request timed out" message = "faultCode:Client.Error.RequestTimeout faultString:'Request timed out' faultDetail:'The request timeout for the sent message was reached without receiving a response from the server.'" name = "Error" rootCause = (null) It's strange it seems that the server takes a long time to responde, then (in the service browser) flash made a new call to the server and the old one get a response. Some problem with sessions ? Really no idea ....

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• Threading models when talking to hardware devices

  - by Fuzz

  When writing an interface to hardware over a communication bus, communications timing can sometimes be critical to the operation of a device. As such, it is common for developers to spin up new threads to handle communications. It can also be a terrible idea to have a whole bunch of threads in your system, an in the case that you have multiple hardware devices you may have many many threads that are out of control of the main application. Certainly it can be common to have two threads per device, one for reading and one for writing. I am trying to determine the pros and cons of the two different models I can think of, and would love the help of the Programmers community. Each device instance gets handles it's own threads (or shares a thread for a communication device). A thread may exist for writing, and one for reading. Requested writes to a device from the API are buffered and worked on by the writer thread. The read thread exists in the case of blocking communications, and uses call backs to pass read data to the application. Timing of communications can be handled by the communications thread. Devices aren't given their own threads. Instead read and write requests are queued/buffered. The application then calls a "DoWork" function on the interface and allows all read and writes to take place and fire their callbacks. Timing is handled by the application, and the driver can request to be called at a given specific frequency. Pros for Item 1 include finer grain control of timing at the communication level at the expense of having control of whats going on at the higher level application level (which for a real time system, can be terrible). Pros for Item 2 include better control over the timing of the entire system for the application, at the expense of allowing each driver to handle it's own business. If anyone has experience with these scenarios, I'd love to hear some ideas on the approaches used.

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• Ubuntu 12.04 slow boot on ASUS, attached with dmesg and bootchart

  - by stanleyhunk

  I heard that Ubuntu can boot up around 30sec, but I take more than 60sec every time my Ubuntu boot. I also read some forum said need to post the dmesg and bootchart to identify which process slowing down the booting time, as I'm not expert in Ubuntu and wish to learn more about it, I humbly ask any pro here to teach me how. My laptop specs: Model : ASUS K45VS RAM : 8MB CPU : Intel(R) Core(TM) i7-3630QM CPU @ 2.40GHz x 8 Graphic Card : nVidia GeForce GT 645M HDD : 750GB OS : Single boot Ubuntu 12.04LTS System.uname : Linux 3.8.0-39-generic #58~precise1-Ubuntu SMP Fri May 2 21:33:40 UTC 2014 x86_64 System.release : Ubuntu 12.04.4 LTS System.kernel.options : BOOT_IMAGE=/boot/vmlinuz-3.8.0-39-generic root=UUID=c8a71503-bce8-406c-9a5f-5aa8284f5c7c ro quiet splash My dmesg (which highlighted to the huge time frame gap): [ 30.772656] cgroup: libvirtd (1961) created nested cgroup for controller "memory" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 30.772659] cgroup: "memory" requires setting use_hierarchy to 1 on the root. [ 30.772683] cgroup: libvirtd (1961) created nested cgroup for controller "devices" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 30.772710] cgroup: libvirtd (1961) created nested cgroup for controller "blkio" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 32.140335] nvidia 0000:01:00.0: irq 46 for MSI/MSI-X [ 32.505619] ACPI Error: Field [TMPB] at 1081344 exceeds Buffer [ROM1] size 262144 (bits) (20121018/dsopcode-236) [ 32.505624] ACPI Error: Method parse/execution failed [\_SB_.PCI0.PEG0.PEGP._ROM] (Node ffff880224e91f00), AE_AML_BUFFER_LIMIT (20121018/psparse-537) [ 802.034422] audit_printk_skb: 69 callbacks suppressed [ 802.034428] type=1400 audit(1400914804.392:35): apparmor="DENIED" operation="capable" parent=1 profile="/usr/sbin/cupsd" pid=1683 comm="cupsd" pid=1683 comm="cupsd" capability=36 capname="block_suspend" [ 1581.300901] type=1400 audit(1400915584.816:36): apparmor="DENIED" operation="capable" parent=1 profile="/usr/sbin/cupsd" pid=1683 comm="cupsd" pid=1683 comm="cupsd" capability=36 capname="block_suspend" My Bootchart.png: Looking forward to learn to improve both my booting time and knowledge. Thanks in advance :)

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• How to disable autocmd or augroup in vim?

  - by Andrew Vit

  Given I have a group of commands such as: augroup MyGroup autocmd CursorMoved * silent call MyCommandOne() augroup END I want to disable all the autocommands in MyGroup for a time and then re-enable it later. Is there anything I can do with the group? Specifically, is there a way to disable the whole group at once? If not, what can I do to disable individual commands? Looking at the help, I only see a few options: augroup! will delete the whole group: I don't think this is right since I will want to re-enable it again. (But maybe there's a way to easily redefine the group again?) :noautocmd will only disable the callbacks for a one-off invocation of a command. (And it disables all autocmds, not specified ones) eventignore addresses the event binding, not the command: it sounds like it disables all bound commands for a given event, not just one command or a group I can specify. How is this done?

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• Why would Java app make RPC call to itself?

  - by amphibient

  I am working with a multithreaded homegrown multi-module app in my new job. We use the the Thrift protocol to communicate RPC calls between different stand-alone applications in a distributed system. One of them listens on multiple ports and I just noticed that it actually makes an RPC call to itself from one thread invoked from one socket it listens to (web service call) to another port within the same app. I verified that it could accomplish the same thing if it just went and directly called the method that the remote procedure ultimately invokes as it is all within the same application, same JVM. To make it even more mysterious, the call is completely synchronous, i.e. no callbacks involved. The first thread totally sits and waits until it makes a call across the wire to itself and comes back. Now, I am perplexed why anybody would do it this way. It seems like calling somebody on the phone that sits in the same room as you do. Can anybody provide an explanation why the developer before me would come up with the above mentioned model? Maybe there is a reason and I am missing something.

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• Using C++ but not using the language's specific features, should switch to C?

  - by Petruza

  I'm developing a NES emulator as a hobby, in my free time. I use C++ because is the language I use mostly, know mostly and like mostly. But now that I made some advance into the project I realize I'm not using almost any specific features of C++, and could have done it in plain C and getting the same result. I don't use templates, operator overloading, polymorphism, inheritance. So what would you say? should I stay in C++ or rewrite it in C? I won't do this to gain in performance, it could come as a side effect, but the idea is why should I use C++ if I don't need it? The only features of C++ I'm using is classes to encapsulate data and methods, but that can be done as well with structs and functions, I'm using new and delete, but could as well use malloc and free, and I'm using inheritance just for callbacks, which could be achieved with pointers to functions. Remember, it's a hobby project, I have no deadlines, so the overhead time and work that would require a re-write are not a problem, might be fun as well. So, the question is C or C++?

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• Binding in the view or the controller?

  - by da_b0uncer

  I've seen 2 different approaches with MVC on the web. One, like in ExtJS, is to bind the callbacks to the view via the controller. Finding every element on the view and adding the functionallity. The other, like in angular.js and in the lift-framework server-side, too, is to bind in the views and just write the functionallity in the controller. Which is better and cleaner? The ExtJS approach has dumb views and all the logic in the controller. Which seems clean to me. I had problems with global IDs for GUI-elements or relative navigation to GUI-elements in this approach. When I changed the view, the controller couldn't find the buttons anymore or I had multiple instances of one button with the same ID on a single application, because of the global ID. But I solved this with IDs that are only global in a view and can be on the application multiple times. So I could mess with the (dumb) views layout and design and the functionallity wouldn't break. The angular.js approach with the bindings in the view don't has the problem with global IDs. Also, the person who changes something in the view layout has to know the IDs anyway, so the controller can put the data at the right spot. So if I write <a ng-click="doThis()" /> for angular.js and implement doThis() or <a lid="buttonwhichdoesthis" /> for extjs and find the element with the local id and add doThis() as handler on the controller side, seems to be not so different. The only thing is, the second one has one more layer of indirection, which seems cleaner. The first one seems somehow to cost less effort.

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• Why using Fragments?

  - by ahmed_khan_89

  I have read the documentation and some other questions' threads about this topic and I don't really feel convinced; I don't see clearly the limits of use of this technique. Fragments are now seen as a Best Practice; every Activity should be basically a support for one or more Fragments and not call a layout directly. Fragments are created in order to: allow the Activity to use many fragments, to change between them, to reuse these units... == the Fragment is totally dependent to the Context of an activity , so if I need something generic that I can reuse and handle in many Activities, I can create my own custom layouts or Views ... I will not care about this additional Complexity Developing Layer that fragments would add. a better handling to different resolution == OK for tablets/phones in case of long process that we can show two (or more) fragments in the same Activity in Tablets, and one by one in phones. But why would I use fragments always ? handling callbacks to navigate between Fragments (i.e: if the user is Logged-in I show a fragment else I show another fragment). === Just try to see how many bugs facebook SDK Log-in have because of this, to understand that it is really (?) ... considering that an Android Application is based on Activities... Adding another life cycles in the Activity would be better to design an Application... I mean the modules, the scenarios, the data management and the connectivity would be better designed, in that way. === This is an answer of someone who's used to see the Android SDK and Android Framework with a Fragments vision. I don't think it's wrong, but I am not sure it will give good results... And it is really abstract... ==== Why would I complicate my life, coding more, in using them always? else, why is it a best practice if it's just a tool for some cases? what are these cases?

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• Crypted_password is null when using Authlogic to save a user

  - by kareem

  i'm getting a strange error on my production install when i try and create a new user using AL: ActiveRecord::StatementInvalid: Mysql::Error: Column 'crypted_password' cannot be null: INSERT INTO users especially strange b/c it works as expected on my local box. RUnning Rails 2.3.2 and ruby 1.8.7 on both boxes. user.rb: class User < ActiveRecord::Base before_create :set_username acts_as_authentic do |c| c.require_password_confirmation = false c.login_field = "email" c.validates_length_of_password_field_options = {:minimum => 4} c.validate_login_field = false #don't validate email field with additional validations end end Here's output from my production console: >> u = User.new => #<User id: nil, username: nil, email: nil, crypted_password: nil, password_salt: nil, persistence_token: nil, single_access_token: nil, perishable_token: nil, login_count: 0, failed_login_count: 0, last_request_at: nil, current_login_at: nil, last_login_at: nil, current_login_ip: nil, last_login_ip: nil, created_at: nil, updated_at: nil, is_admin: 0, first_name: nil, last_name: nil> >> u.full_name = 'john smith' => "john smith" >> u.password = 'test' => "test" >> u.email = '[email protected]' => "[email protected]" >> u.valid? => true >> u.save ActiveRecord::StatementInvalid: Mysql::Error: Column 'crypted_password' cannot be null: INSERT INTO `users` (`single_access_token`, `last_request_at`, `created_at`, `crypted_password`, `perishable_token`, `updated_at`, `username`, `failed_login_count`, `current_login_ip`, `password_salt`, `current_login_at`, `is_admin`, `persistence_token`, `login_count`, `last_name`, `last_login_ip`, `last_login_at`, `email`, `first_name`) VALUES('B-XSXwhO7hkbtISIOyEq', NULL, '2009-07-31 01:10:44', NULL, 'FK3mYS2Tp5Tzeq5IXE1z', '2009-07-31 01:10:44', 'john', 0, NULL, NULL, NULL, 0, '2c76b645f761eb3509353290e93874cecdb68a63caa165812ab1b126d63660757090ecf69995caef9e78f93d070b524e2542b3fec4ee050726088c2a9fdb0c9f', 0, 'smith', NULL, NULL, '[email protected]', 'john') from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/connection_adapters/abstract_adapter.rb:212:in `log' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/connection_adapters/mysql_adapter.rb:320:in `execute' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/connection_adapters/abstract/database_statements.rb: 259:in `insert_sql' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/connection_adapters/mysql_adapter.rb:330:in `insert_sql' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/connection_adapters/abstract/database_statements.rb: 44:in `insert_without_query_dirty' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/connection_adapters/abstract/query_cache.rb:18:in `insert' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/base.rb:2902:in `create_without_timestamps' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/timestamp.rb:29:in `create_without_callbacks' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/callbacks.rb:266:in `create' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/base.rb:2868:in `create_or_update_without_callbacks' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/callbacks.rb:250:in `create_or_update' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/base.rb:2539:in `save_without_validation' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/validations.rb:1009:in `save_without_dirty' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/dirty.rb:79:in `save_without_transactions' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/transactions.rb:229:in `send' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/transactions.rb:229:in `with_transaction_returning_status' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/connection_adapters/abstract/database_statements.rb: 136:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/transactions.rb:182:in `transaction' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/transactions.rb:228:in `with_transaction_returning_status' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/transactions.rb:196:in `save' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/transactions.rb:208:in `rollback_active_record_state!' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/ active_record/transactions.rb:196:in `save' No idea why this is happening, and especially why this saves a new user on dev but not on production. Any help is much appreciated, thanks! edit: using Apache & Passenger 2.2.4

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• Linking LLVM JIT Code to Static LLVM Libraries?

  - by inflector

  I'm in the process of implementing a cross-platform (Mac OS X, Windows, and Linux) application which will do lots of CPU intensive analysis of financial data. The bulk of the analysis engine will be written in C++ for speed reasons, with a user-accessible scripting engine interfacing with the C++ testing engine. I want to write several scripting front-ends over time to emulate other popular software with existing large user bases. The first front will be a VisualBasic-like scripting language. I'm thinking that LLVM would be perfect for my needs. Performance is very important because of the sheer amount of data; it can take hours or days to run a single run of tests to get an answer. I believe that using LLVM will also allow me to use a single back-end solution while I implement different front-ends for different flavors of the scripting language over time. The testing engine itself will be separated from the interface and testing will even take place in a separate process with progress and results being reported to the testing management interface. Tests will consist of scripting code integrated with the testing engine code. In a previous implementation of a similar commercial testing system I wrote, I built a fast interpreter which easily interfaced with the testing library because it was written in C++ and linked directly to the testing engine library. Callbacks from scripting code to testing library objects involved translating between the formats with significant overhead. I'm imagining that with LLVM, I could implement the callbacks into C++ directly so that I could make the scripting code work almost as if it had been written in C++. Likewise, if all the code was compiled to LLVM byte-code format, it seems like the LLVM optimizers could optimize across the boundaries between the scripting language and the testing engine code that was written in C++. I don't want to have to compile the testing engine every time. Ideally, I'd like to JIT compile only the scripting code. For small tests, I'd skip some optimization passes, while for large tests, I'd perform full optimizations during the link. So is this possible? Can I precompile the testing engine to a .o object file or .a library file and then link in the scripting code using the JIT? Finally, ideally, I'd like to have the scripting code implement specific methods as subclasses for a specific C++ class. So the C++ testing engine would only see C++ objects while the JIT setup code compiled scripting code that implemented some of the methods for the objects. It seems that if I used the right name mangling algorithm it would be relatively easy to set up the LLVM generation for the scripting language to look like a C++ method call which could then be linked into the testing engine. Thus the linking stage would go in two directions, calls from the scripting language into the testing engine objects to retrieve pricing information and test state information and calls from the testing engine of methods of some particular C++ objects where the code was supplied not from C++ but from the scripting language. In summary: 1) Can I link in precompiled (either .bc, .o, or .a) files as part of the JIT compilation, code-generation process? 2) Can I link in code using that the process in 1) above in such a way that I am able to create code that acts as if it was all written in C++?

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• Async networking + threading problem

  - by randallmeadows

  I kick off a network request, assuming no login credentials are required to talk to the destination server. If they are required, then I get an authentication challenge, at which point I display a view requesting said credentials from the user. When they are supplied, I restart the network request, using those credentials. That's all fine and dandy, as long as I only do one request at a time. But I'm not, typically. When both requests are kicked off, I get the first challenge, and present the prompt (using -presentModalViewController:). Then the 2nd challenge comes in. And I crash when it tries to display the 2nd prompt. I have the bulk of this wrapped in an @synchronized() block, but this has no effect because these delegate methods are all being called on the same (main) thread. The docs say the delegate methods are called on the same thread in which the connection was started. OK, no problem; I'll just write a method that I run on a background thread using -performSelectorInBackground: NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO]; [connections addObject:connection]; [self performSelectorInBackground:@selector(startConnection:) withObject:connection]; [connection release]; - (void)startConnection:(NSURLConnection *)connection { NSAutoreleasePool *pool = [NSAutoreleasePool new]; [connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [connection start]; [pool drain]; } which should put every network request, and its callbacks, on its own thread, and then my @synchronized() blocks will take effect. The docs for -initWithRequest:... state "Messages to the delegate will be sent on the thread that calls this method. By default, for the connection to work correctly the calling thread’s run loop must be operating in the default run loop mode." Ok, I'm doing that. They also state "If you pass NO [for startImmediately], you must schedule the connection in a run loop before starting it." OK, I'm doing that, too. Furthermore, the docs for NSRunLoop state "Each NSThread object, including the application’s main thread, has an NSRunLoop object automatically created for it as needed. If you need to access the current thread’s run loop, you do so with the class method currentRunLoop." I'm assuming this applies to the background thread created by the call -performSelectorInBackground... (which does appear to be the case, when I execute 'po [NSClassFromString(@"NSRunLoop") currentRunLoop]' in the -startConnection: method). The -startConnection: method is indeed being called. But after kicking off the connection, I now never get any callbacks on it. None of the -connectionDid… delegate methods. (I even tried explicitly starting the thread's run loop, but that made no difference; I've used threads like this before, and I've never had to start the run loop manually before--but I'm now grasping at straws...) I think I've come up with a workaround such that I only handle one request at a time, but it's kludgy and I'd like to do this the Right Way. But, what am I missing here? Thanks! randy

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• MSDTC attempts to enlist client machine in a distributed transaction

  - by Ken

  Hi there We're seeing the following intermittent warning logged by MSDTC: A caller has attempted to propagate a transaction to a remote system, but MSDTC network DTC access is currently disabled on machine 'X'. Please review the MS DTC configuration settings. However, MSDTC is disabled on machine X by design - it's a client machine, and has no business being enlisted in the transaction! Several windows service endpoints hosting WCF services over TCP Single SQL Server 2005 instance beneath Linq to Sql Remote client receives event callbacks over WCF/TCP The issue is tricky to reproduce - usually following restart of services. We suspect a callback to the client machine is occurring within the context of a transaction. Just wondering if anyone has seen similar issues?? Ken

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• How to achieve maximum callback throughput with WCF duplex channels

  - by Schneider

  I have setup a basic WCF client/server which are communicating via Named pipes. It is a duplex contract with a callback. After the client "subscribes", a thread on the server just invokes the callback as quickly as possible. The problem is I am only getting a throughput of 1000 callbacks per second. And the payload is only an integer! I need to get closer to 10,000. Everything is essentially running with default settings. What can I look at to improve things, or should I just drop WCF for some other technology? Thanks

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