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  • Ways to organize interface and implementation in C++

    - by Felix Dombek
    I've seen that there are several different paradigms in C++ concerning what goes into the header file and what to the cpp file. AFAIK, most people, especially those from a C background, do: foo.h class foo { private: int mem; int bar(); public: foo(); foo(const foo&); foo& operator=(foo); ~foo(); } foo.cpp #include foo.h foo::bar() { return mem; } foo::foo() { mem = 42; } foo::foo(const foo& f) { mem = f.mem; } foo::operator=(foo f) { mem = f.mem; } foo::~foo() {} int main(int argc, char *argv[]) { foo f; } However, my lecturers usually teach C++ to beginners like this: foo.h class foo { private: int mem; int bar() { return mem; } public: foo() { mem = 42; } foo(const foo& f) { mem = f.mem; } foo& operator=(foo f) { mem = f.mem; } ~foo() {} } foo.cpp #include foo.h int main(int argc, char* argv[]) { foo f; } // other global helper functions, DLL exports, and whatnot Originally coming from Java, I have also always stuck to this second way for several reasons, such as that I only have to change something in one place if the interface or method names change, that I like the different indentation of things in classes when I look at their implementation, and that I find names more readable as foo compared to foo::foo. I want to collect pro's and con's for either way. Maybe there are even still other ways? One disadvantage of my way is of course the need for occasional forward declarations.

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  • How to do Cross Platform in own Engine? [on hold]

    - by Mineorbit
    At the Moment I finished the first game with my game engine(if I wanna call it like that) which is based in LWJGL. Now i'm worring if I could do crossplattforming in my engine. I build me a tool tool with a batch file to compile my project dir into an .exe . At first i'm looking to do it on Android with an comparable batch file. An link for an tutorial would be awesome! At next place there would be an renderer and audiosystem. If read that theres an OpenGL ES renderer, and I allready played a bit around with the Android SDK. But I use the Texture and Audio class in slick-util. So I thought about creating OOP classes that carry around the data and load it in an platform specific Buffer. A Link for an equaly easy-to-use Texture or Audio class would be awesome! Thats all for now! Answers would be awesome! Thanks, Mineorbit!

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  • Use CompiledQuery.Compile to improve LINQ to SQL performance

    - by Michael Freidgeim
    After reading DLinq (Linq to SQL) Performance and in particular Part 4  I had a few questions. If CompiledQuery.Compile gives so much benefits, why not to do it for all Linq To Sql queries? Is any essential disadvantages of compiling all select queries? What are conditions, when compiling makes whose performance, for how much percentage? World be good to have default on application config level or on DBML level to specify are all select queries to be compiled? And the same questions about Entity Framework CompiledQuery Class. However in comments I’ve found answer  of the author ricom 6 Jul 2007 3:08 AM Compiling the query makes it durable. There is no need for this, nor is there any desire, unless you intend to run that same query many times. SQL provides regular select statements, prepared select statements, and stored procedures for a reason.  Linq now has analogs. Also from 10 Tips to Improve your LINQ to SQL Application Performance   If you are using CompiledQuery make sure that you are using it more than once as it is more costly than normal querying for the first time. The resulting function coming as a CompiledQuery is an object, having the SQL statement and the delegate to apply it.  And your delegate has the ability to replace the variables (or parameters) in the resulting query. However I feel that many developers are not informed enough about benefits of Compile. I think that tools like FxCop and Resharper should check the queries  and suggest if compiling is recommended. Related Articles for LINQ to SQL: MSDN How to: Store and Reuse Queries (LINQ to SQL) 10 Tips to Improve your LINQ to SQL Application Performance Related Articles for Entity Framework: MSDN: CompiledQuery Class Exploring the Performance of the ADO.NET Entity Framework - Part 1 Exploring the Performance of the ADO.NET Entity Framework – Part 2 ADO.NET Entity Framework 4.0: Making it fast through Compiled Query

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  • Implementing a ILogger interface to log data

    - by Jon
    I have a need to write data to file in one of my classes. Obviously I will pass an interface into my class to decouple it. I was thinking this interface will be used for testing and also in other projects. This is my interface: //This could be used by filesystem, webservice public interface ILogger { List<string> PreviousLogRecords {get;set;} void Log(string Data); } public interface IFileLogger : ILogger { string FilePath; bool ValidFileName; } public class MyClassUnderTest { public MyClassUnderTest(IFileLogger logger) {....} } [Test] public void TestLogger() { var mock = new Mock<IFileLogger>(); mock.Setup(x => x.Log(Is.Any<string>).AddsDataToList()); //Is this possible?? var myClass = new MyClassUnderTest(mock.Object); myClass.DoSomethingThatWillSplitThisAndLog3Times("1,2,3"); Assert.AreEqual(3,mock.PreviousLogRecords.Count); } This won't work I don't believe as nothing is storing the items so is this possible using Moq and also what do you think of the design of the interface?

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  • Android: how do I switch between game scenes in a game? Any tutorials?

    - by Flavio
    I am trying to create a simple game using the Android SDK without using AndEngine (or any other game engine). I have plenty of experience designing games from the past, but I'm having lots of trouble trying to use the Android SDK to make my game. By far my biggest hurdle right now is switching between views. That is, for example, going from the menu to the first level, etc. I am using a traditional model I learned (I think it's called a scene stack or something?) in which you push the current scene onto a stack and the game's main loop runs the top item of the stack. This model seems non-trivial to implement in the Android SDK, mostly because Android seems to be picky about which thread instantiates which view. My issue is that I want the first level to show up when you press a button on the main menu, but when I instantiate the first level (the level class extends SurfaceView and implements SurfaceHolder.Callback) I get a runtime error complaining that the thread that runs the main menu can't instantiate this class. Something about calling Looper.prepare(). I figured at this point I was probably doing things wrong. I'm not sure how to specifically phrase my issue into a question, so maybe I should leave it as either 1) Does anybody know a good way (or the 'proper' way) to switch between scenes in an Android game? or 2) Are there any tutorials out there which show how to create a game that doesn't take place entirely in one scene? (I have googled for a while to no avail... maybe someone else knows of one?) Thanks!

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  • Need advice on framework design: how to make extending easy

    - by beginner_
    I'm creating a framework/library for a rather specific use-case (data type). It uses diverse spring components, including spring-data. The library has a set of entity classes properly set up and according service and dao layers. The main work or main benefit of the framework lies in the dao and service layer. Developers using the framework should be able to extend my entity classes to add additional fields they require. Therefore I made dao and service layer generic so it can be used by such extended entity classes. I now face an issue in the IO part of the framework. It must be able to import the according "special data type" into the database. In this part I need to create a new entity instance and hence need the actual class used. My current solution is to configure in spring a bean of the actual class used. The problem with this is that an application using the framework could only use 1 implementation of the entity (the original one from me or exactly 1 subclass but not 2 different classes of the same hierarchy. I'm looking for suggestions / desgins for solving this issue. Any ideas?

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  • Using PreApplicationStartMethod for ASP.NET 4.0 Application to Initialize assemblies

    - by ChrisD
    Sometimes your ASP.NET application needs to hook up some code before even the Application is started. Assemblies supports a custom attribute called PreApplicationStartMethod which can be applied to any assembly that should be loaded to your ASP.NET application, and the ASP.NET engine will call the method you specify within it before actually running any of code defined in the application. Lets discuss how to use it using Steps : 1. Add an assembly to an application and add this custom attribute to the AssemblyInfo.cs. Remember, the method you speicify for initialize should be public static void method without any argument. Lets define a method Initialize. You need to write : [assembly:PreApplicationStartMethod(typeof(MyInitializer.InitializeType), "InitializeApp")] 2. After you define this to an assembly you need to add some code inside InitializeType.InitializeApp method within the assembly. public static class InitializeType {     public static void InitializeApp()     {           // Initialize application     } } 3. You must reference this class library so that when the application starts and ASP.NET starts loading the dependent assemblies, it will call the method InitializeApp automatically. Warning Even though you can use this attribute easily, you should be aware that you can define these kind of method in all of your assemblies that you reference, but there is no guarantee in what order each of the method to be called. Hence it is recommended to define this method to be isolated and without side effect of other dependent assemblies. The method InitializeApp will be called way before the Application_start event or even before the App_code is compiled. This attribute is mainly used to write code for registering assemblies or build providers. Read Documentation I hope this post would come helpful.

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  • What is wrong with my game loop/mechanic?

    - by elias94xx
    I'm currently working on a 2d sidescrolling game prototype in HTML5 canvas. My implementations so far include a sprite, vector, loop and ticker class/object. Which can be viewed here: http://elias-schuett.de/apps/_experiments/2d_ssg/js/ So my game essentially works well on todays lowspec PC's and laptops. But it does not on an older win xp machine I own and on my Android 2.3 device. I tend to get ~10 FPS with these devices which results in a too high delta value, which than automaticly gets fixed to 1.0 which results in a slow loop. Now I know for a fact that there is a way to implement a super smooth 60 or 30 FPS loop on both devices. Best example would be: http://playbiolab.com/ I don't need all the chunk and debugging technology impact.js offers. I could even write a super simple game where you just control a damn square and it still wouldn't run on a equally fast 30 or 60 fps. Here is the Loop class/object I'm using. It requires a requestAnimationFrame unify function. Both devices I've tested my game on support requestAnimationFrame, so there is no interval fallback. var Loop = function(callback) { this.fps = null; this.delta = 1; this.lastTime = +new Date; this.callback = callback; this.request = null; }; Loop.prototype.start = function() { var _this = this; this.request = requestAnimationFrame(function(now) { _this.start(); _this.delta = (now - _this.lastTime); _this.fps = 1000/_this.delta; _this.delta = _this.delta / (1000/60) > 2 ? 1 : _this.delta / (1000/60); _this.lastTime = now; _this.callback(); }); }; Loop.prototype.stop = function() { cancelAnimationFrame(this.request); };

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  • Why to say, my function is of IFly type rather than saying it's Airplane type

    - by Vishwas Gagrani
    Say, I have two classes: Airplane and Bird, both of them fly. Both implement the interface IFly. IFly declares a function StartFlying(). Thus both Airplane and Bird have to define the function, and use it as per their requirement. Now when I make a manual for class reference, what should I write for the function StartFlying? 1) StartFlying is a function of type IFly . 2) StartFlying is a function of type Airplane 3) StartFlying is a function of type Bird. My opinion is 2 and 3 are more informative. But what i see is that class references use the 1st one. They say what interface the function is declared in. Problem is, I really don't get any usable information from knowing StartFlying is IFly type. However, knowing that StartFlying is a function inside Airplane and Bird, is more informative, as I can decide which instance (Airplane or Bird ) to use. Any lights on this: how saying StartFlying is a function of type IFly, can help a programmer understanding how to use the function?

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  • Is there a precedent for the license on a compiler restricting the kind of development you can use it for?

    - by Jim McKeeth
    It was recently let slip that the new EULA for Delphi XE3 will prohibit Client Server development with the Professional edition without the additional purchase of a Client Server license pack. This is not to say the Professional version will lack the features, but the license will specifically prohibit the developer from using the compiler for a specific class of development, even with 3rd party or home grown solutions. So my question is if there is a precedent of a compiler or similar creative tool prohibiting the class of work you can use it for. Specifically a commercially licensed "professional" tool like Delphi XE3. Also, would such a restriction be legally enforceable? I know there have been educational edition or starter edition tools in the past that have restricted their use for commercial purposes, but those were not sold as "professional" tools. Also I know that a lot of computing software and equipment will have a disclaimer that it is not for use in "life support equipment" or "nuclear power" but that is more of avoiding liability than prohibiting activity. Seems like I recall Microsoft putting a restriction in FrontPage that you couldn't use it to create a web site that reflected poorly on Microsoft, but they pulled that restriction before it could be tested legally.

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  • Object oriented EDI handling in PHP

    - by Robert van der Linde
    I'm currently starting a new sub project where I will: Retrieve the order information from our mainframe Save the order information to our web-apps' database Send the order as EDI (either D01b or D93a) Receive the order response, despatch advice and invoice messages Do all kinds of fun things with the resulting datasets. However I am struggling with my initial class designs. The order information will be retrieved from the mainframe which will result in a "AOrder" class, this isn't a problem, I am not sure about how to mold this local object into an EDI string. Should I create EDIOrder/EDIOrderResponse/etc classes with matching decorators (EDIOrderD01BDecorator, EDIOrderD93ADecorator)? Do I need builder objects or can I do: // $myOrder is instance of AOrder $myOrder->toEDIOrder(); $decorator = new EDIOrderD01BDecorator($myOrder); $edi = $decorator->getEDIString(); And it'll have to work the other way around as well. Is the following code a good way of handling this problem or should I go about this differently? $ediString = $myEDIMessageBroker->fetch(); $ediOrderResponse = EDIOrderResponse::fromString($ediString); I'm just not so sure about how I should go about designing the classes and interactions between them. Thanks for reading and helping.

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  • Take care to unhook Anonymous Delegates

    - by David Vallens
    Anonymous delegates are great, they elimiante the need for lots of small classes that just pass values around, however care needs to be taken when using them, as they are not automatically unhooked when the function you created them in returns. In fact after it returns there is no way to unhook them. Consider the following code.   using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Diagnostics; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { SimpleEventSource t = new SimpleEventSource(); t.FireEvent(); FunctionWithAnonymousDelegate(t); t.FireEvent(); } private static void FunctionWithAnonymousDelegate(SimpleEventSource t) { t.MyEvent += delegate(object sender, EventArgs args) { Debug.WriteLine("Anonymous delegate called"); }; t.FireEvent(); } } public class SimpleEventSource { public event EventHandler MyEvent; public void FireEvent() { if (MyEvent == null) { Debug.WriteLine("Attempting to fire event - but no ones listening"); } else { Debug.WriteLine("Firing event"); MyEvent(this, EventArgs.Empty); } } } } If you expected the anonymous delegates do die with the function that created it then you would expect the output Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledAttempting to fire event - but no ones listening However what you actually get is Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledFiring eventAnonymous delegate called In my example the issue is just slowing things down, but if your delegate modifies objects, then you could end up with dificult to diagnose bugs. A solution to this problem is to unhook the delegate within the function var myDelegate = delegate(){Console.WriteLine("I did it!");}; MyEvent += myDelegate; // .... later MyEvent -= myDelegate;

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  • Hijacking ASP.NET Sessions

    - by Ricardo Peres
    So, you want to be able to access other user’s session state from the session id, right? Well, I don’t know if you should, but you definitely can do that! Here is an extension method for that purpose. It uses a bit of reflection, which means, it may not work with future versions of .NET (I tested it with .NET 4.0/4.5). 1: public static class HttpApplicationExtensions 2: { 3: private static readonly FieldInfo storeField = typeof(SessionStateModule).GetField("_store", BindingFlags.NonPublic | BindingFlags.Instance); 4:  5: public static ISessionStateItemCollection GetSessionById(this HttpApplication app, String sessionId) 6: { 7: var module = app.Modules["Session"] as SessionStateModule; 8:  9: if (module == null) 10: { 11: return (null); 12: } 13:  14: var provider = storeField.GetValue(module) as SessionStateStoreProviderBase; 15:  16: if (provider == null) 17: { 18: return (null); 19: } 20:  21: Boolean locked; 22: TimeSpan lockAge; 23: Object lockId; 24: SessionStateActions actions; 25:  26: var data = provider.GetItem(HttpContext.Current, sessionId.Trim(), out locked, out lockAge, out lockId, out actions); 27:  28: if (data == null) 29: { 30: return (null); 31: } 32:  33: return (data.Items); 34: } 35: } As you can see, it extends the HttpApplication class, that is because we need to access the modules collection, for the Session module. Use with care!

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  • Nested entities in Google App Engine. Do I do it right?

    - by Aleksandr Makov
    Trying to make most of the GAE Datastore entities concept, but some doubts drill my head. Say I have the model: class User(ndb.Model): email = ndb.StringProperty(indexed=True) password = ndb.StringProperty(indexed=False) first_name = ndb.StringProperty(indexed=False) last_name = ndb.StringProperty(indexed=False) created_at = ndb.DateTimeProperty(auto_now_add=True) @classmethod def key(cls, email): return ndb.Key(User, email) @classmethod def Add(cls, email, password, first_name, last_name): user = User(parent=cls.key(email), email=email, password=password, first_name=first_name, last_name=last_name) user.put() UserLogin.Record(email) class UserLogin(ndb.Model): time = ndb.DateTimeProperty(auto_now_add=True) @classmethod def Record(cls, user_email): login = UserLogin(parent=User.key(user_email)) login.put() And I need to keep track of times of successful login operations. Each time user logs in, an UserLogin.Record() method will be executed. Now the question — do I make it right? Thanks. EDIT 2 Ok, used the typed arguments, but then it raised this: Expected Key instance, got User(key=Key('User', 5418393301680128), created_at=datetime.datetime(2013, 6, 27, 10, 12, 25, 479928), email=u'[email protected]', first_name=u'First', last_name=u'Last', password=u'password'). It's clear to understand, but I don't get why the docs are misleading? They implicitly propose to use: # Set Employee as Address entity's parent directly... address = Address(parent=employee) But Model expects key. And what's worse the parent=user.key() swears that key() isn't callable. And I found out the user.key works. EDIT 1 After reading the example form the docs and trying to replicate it — I got type error: TypeError('Model constructor takes no positional arguments.'). This is the exacto code used: user = User('[email protected]', 'password', 'First', 'Last') user.put() stamp = UserLogin(parent=user) stamp.put() I understand that Model was given the wrong argument, BUT why it's in the docs?

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  • Why do memory-managed languages retain the `new` keyword?

    - by Channel72
    The new keyword in languages like Java, Javascript, and C# creates a new instance of a class. This syntax seems to have been inherited from C++, where new is used specifically to allocate a new instance of a class on the heap, and return a pointer to the new instance. In C++, this is not the only way to construct an object. You can also construct an object on the stack, without using new - and in fact, this way of constructing objects is much more common in C++. So, coming from a C++ background, the new keyword in languages like Java, Javascript, and C# seemed natural and obvious to me. Then I started to learn Python, which doesn't have the new keyword. In Python, an instance is constructed simply by calling the constructor, like: f = Foo() At first, this seemed a bit off to me, until it occurred to me that there's no reason for Python to have new, because everything is an object so there's no need to disambiguate between various constructor syntaxes. But then I thought - what's really the point of new in Java? Why should we say Object o = new Object();? Why not just Object o = Object();? In C++ there's definitely a need for new, since we need to distinguish between allocating on the heap and allocating on the stack, but in Java all objects are constructed on the heap, so why even have the new keyword? The same question could be asked for Javascript. In C#, which I'm much less familiar with, I think new may have some purpose in terms of distinguishing between object types and value types, but I'm not sure. Regardless, it seems to me that many languages which came after C++ simply "inherited" the new keyword - without really needing it. It's almost like a vestigial keyword. We don't seem to need it for any reason, and yet it's there. Question: Am I correct about this? Or is there some compelling reason that new needs to be in C++-inspired memory-managed languages like Java, Javascript and C#?

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  • Why do I get this Debug Assertion Failed? Expression: list iterator not dereferenceable [migrated]

    - by Karel
    I'm trying this example in the (translated to dutch) book of Bjarne Stroustrup (C++): #include <vector> #include <list> #include "complex.h" complex ac[200]; std::vector<complex> vc; std::list<complex> l; template<class In, class Out> void Copy(In from, In too_far, Out to) { while(from != too_far) { *to = *from; ++to; ++from; } } void g(std::vector<complex>& vc , std::list<complex>& lc) { Copy(&ac[0], &ac[200], lc.begin()); // generates debug error Copy(lc.begin(), lc.end(), vc.begin()); // also generates debug error } void f() { ac[0] = complex(10,20); g(vc, l); } int main () { f(); } ** Compiling and Linking goes successful (0 errors/warnings)** But at runtime I get this error: Debug Assertion Failed! Program: path to exe file: \program files\ms vs studio 10.0\vc\include\list Line: 207 Expression: list iterator not dereferenceable For information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts. (Press retry to debug the application)

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  • What is meant by, "A user shouldn't decide whether it is an Admin or not. The Privileges or Security system should."

    - by GlenPeterson
    The example used in the question pass bare minimum data to a function touches on the best way to determine whether the user is an administrator or not. One common answer was: user.isAdmin() This prompted a comment which was repeated several times and up-voted many times: A user shouldn't decide whether it is an Admin or not. The Privileges or Security system should. Something being tightly coupled to a class doesn't mean it is a good idea to make it part of that class. I replied, The user isn't deciding anything. The User object/table stores data about each user. Actual users don't get to change everything about themselves. But this was not productive. Clearly there is an underlying difference of perspective which is making communication difficult. Can someone explain to me why user.isAdmin() is bad, and paint a brief sketch of what it looks like done "right"? Really, I fail to see the advantage of separating security from the system that it protects. Any security text will say that security needs to be designed into a system from the beginning and considered at every stage of development, deployment, maintenance, and even end-of-life. It is not something that can be bolted on the side. But 17 up-votes so far on this comment says that I'm missing something important.

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  • BCM2046B1 Bluetooth Dongle connection problem

    - by Andfoy
    Well i have a Blueooth dongle with an BCM2046 IC intrregated, my problem is that when i connect it, Ubuntu recognize it, but it don't work whe i try to scan or scan the PC from other device, i replaced the default Gnome Bluetooth manager and i installed Blueman, but the problem presists. The Bluetooth LED indicator appears to be "working". I'm using 11.10 Oneiric Ocelot hcitool dev: Devices: hci0 89:21:XX:XX:XX:XX lsusb: Bus 002 Device 003: ID 0a5c:4500 Broadcom Corp. BCM2046B1 USB 2.0 Hub (part of BCM2046 Bluetooth) Bus 002 Device 004: ID 0a5c:2100 Broadcom Corp. Bluetooth 2.0+eDR dongle hciconfig -a: hci0: Type: BR/EDR Bus: USB BD Address: 89:21:XX:XX:XX:XX ACL MTU: 1017:8 SCO MTU: 64:0 UP RUNNING PSCAN ISCAN RX bytes:1329 acl:0 sco:0 events:40 errors:0 TX bytes:671 acl:0 sco:0 commands:35 errors:0 Features: 0xff 0xff 0x8d 0xfe 0x9b 0xf9 0x00 0x80 Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 Link policy: RSWITCH HOLD SNIFF PARK Link mode: SLAVE ACCEPT Name: 'ubuntu-0' Class: 0x4a0100 Service Classes: Networking, Capturing, Telephony Device Class: Computer, Uncategorized HCI Version: 2.0 (0x3) Revision: 0x4000 LMP Version: 2.0 (0x3) Subversion: 0x430e Manufacturer: Broadcom Corporation (15) Sorry for my English and thanks for any hints.

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  • Android From Local DB (DAO) to Server sync (JSON) - Design issue

    - by Taiko
    I sync data between my local DB and a Server. I'm looking for the cleanest way to modelise all of this. I have a com.something.db package That contains a Data Helper and couple of DAO classes that represents objects stored in the db (I didn't write that part) com.something.db --public DataHelper --public Employee @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary etc... (all in all 50 fields) I have a com.something.sync package That contains all the implementation detail on how to send data to the server. It boils down to a ConnectionManager that is fed by different classes that implements a 'Request' interface com.something.sync --public interface ConnectionManager --package ConnectionManagerImpl --public interface Request --package LoginRequest --package GetEmployeesRequest My issue is, at some point in the sync process, I have to JSONise and de-JSONise my data (E.g. the Employee class). But I really don't feel like having the same Employee class be responsible for both his JSONisation and his actual representation inside the local database. It really doesn't feel right, because I carefully decoupled the rest, I am only stuck on this JSON thing. What should I do ? Should I write 3 Employee classes ? EmployeeDB @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary -etc... 50 fields EmployeeInterface -getName -getSalary -etc... 50 fields EmployeeJSON -JSON_KEY_NAME = "name" The JSON key happens to be the same as the table name, but it isn't requirement -name -JSON_KEY_SALARY = "salary" -salary -etc... 50 fields It feels like a lot of duplicates. Is there a common pattern I can use there ?

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  • What conventions or frameworks exist for MVVM in Perl?

    - by Will Sheppard
    We're using Catalyst to render lots of webforms in what will become a large application. I don't like the way all the form data is confusingly into a big hash in the Controller, before being passed to the template. It seems jumbled up and messy for the template. I'm sure there are real disadvantages that I haven't described properly... Are there? One solution is to just decide on a convention for the hash, e.g.: { defaults => { type => ['a', 'b', 'c'] }, input => { type => 'a' }, output => { message => "2 widgets found of type a", widgets => [ 'foo', 'bar' ] } } Another way is to store the page/form data as attributes in a class (a ViewModel?), and pass a whole object to the template, which it could use like this: <p class="message">[% model.message %]<p> [% FOREACH widget IN model.widgets %] Which way is more flexible for large applications? Are there any other solutions or existing Catalyst-compatible frameworks?

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  • Checking preconditions or not

    - by Robert Dailey
    I've been wanting to find a solid answer to the question of whether or not to have runtime checks to validate input for the purposes of ensuring a client has stuck to their end of the agreement in design by contract. For example, consider a simple class constructor: class Foo { public: Foo( BarHandle bar ) { FooHandle handle = GetFooHandle( bar ); if( handle == NULL ) { throw std::exception( "invalid FooHandle" ); } } }; I would argue in this case that a user should not attempt to construct a Foo without a valid BarHandle. It doesn't seem right to verify that bar is valid inside of Foo's constructor. If I simply document that Foo's constructor requires a valid BarHandle, isn't that enough? Is this a proper way to enforce my precondition in design by contract? So far, everything I've read has mixed opinions on this. It seems like 50% of people would say to verify that bar is valid, the other 50% would say that I shouldn't do it, for example consider a case where the user verifies their BarHandle is correct, but a second (and unnecessary) check is also being done inside of Foo's constructor.

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  • so, my Cassandra consultant left me and now I'm thinking about reverting to mysql

    - by sathia
    I run a middle size community and some time ago I started to develop social capabilities such as follow, status update, wall etc. For some reason i thought that Cassandra was the right tool for the job so I looked online for a Cassandra developer and I found a very talented one. Unluckily in the midst of the development the dev left (too much jobs) and so I'm here with a very nice class, a very nice demo, but a lot of fears that I won't be able to handle basic things such as compaction, scaling etc. My biggest fear is to go online with all this coolness and then having a site inaccessible for hours or days. The mysql consultant (very talented too) keeps saying me that I should stick with Mysql which I know rather well and in case something's wrong we can manage. In that case I should take the class made for cassandra and abstract it for Mysql. My question is this: Should I find another dev/consultant and stick with Cassandra because for social things it is definitely the best tool for the job, or should I listen to the Mysql consultant and revert to Mysql? About 15k login each day Average 20 actions per user Avg 6 followers x user (These are current statistics, but of course I'd like to increase them as much as possible.)

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  • How to implement child-parent aggregation link in C++?

    - by Giorgio
    Suppose that I have three classes P, C1, C2, composition (strong aggregation) relations between P <>- C1 and P <>- C2, i.e. every instance of P contains an instance of C1 and an instance of C2, which are destroyed when the parent P instance is destroyed. an association relation between instances of C1 and C2 (not necessarily between children of the same P). To implement this, in C++ I normally define three classes P, C1, C2, define two member variables of P of type boost::shared_ptr<C1>, boost::shared_ptr<C2>, and initialize them with newly created objects in P's constructor, implement the relation between C1 and C2 using a boost::weak_ptr<C2> member variable in C1 and a boost::weak_ptr<C1> member variable in C2 that can be set later via appropriate methods, when the relation is established. Now, I also would like to have a link from each C1 and C2 object to its P parent object. What is a good way to implement this? My current idea is to use a simple constant raw pointer (P * const) that is set from the constructor of P (which, in turn, calls the constructors of C1 and C2), i.e. something like: class C1 { public: C1(P * const p, ...) : paren(p) { ... } private: P * const parent; ... }; class P { public: P(...) : childC1(new C1(this, ...)) ... { ... } private: boost::shared_ptr<C1> childC1; ... }; Honestly I see no risk in using a private constant raw pointer in this way but I know that raw pointers are often frowned upon in C++ so I was wondering if there is an alternative solution.

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  • How do you structure your shared code so that it is "re-findable" for new developers?

    - by awmckinley
    I started working at my current job about 8 months ago, and its been one of the best experiences I've had as a young programmer. It's a small company, and both my co-developers are brilliant guys. One of the practices that they both have been encouraging is lots of code-reuse. Our code base is mainly C#, and we're using a centralized revision control system. The way the repository is currently structured, there is a single folder in which all shared class libraries are placed (along with unit tests for each library), and our revision control system allows for sharing or linking those libraries out to other projects. What I'm trying to understand at this point is how the current structure of the folder can be made more conducive for finding those libraries again. I've talked to the other developers about this, and they agree that it's gotten a little messy. I find that I am sometimes "reinventing the wheel" because I didn't realize that there was an existing piece of code that solved a particular problem. The issue is complicated further by the fact that we're sharing some code between ASP.NET MVC2, WinForms, and Windows CE projects, and sharing code between applications built against multiple versions of .NET. How do other people approach this? Is the answer in naming the libraries in a certain way or is it preferable to invest in some code-search software? Is the answer in doc comments? Should we be sharing libraries at all or should we simply branch the class libraries for re-use? Thanks for any and all help!

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  • How to make a player stay within bounds of world with 2D Camera

    - by Craig
    Im creating a simple top down survival game. At the moment, i have the sprite which is a ship and moves by rotating left or right then going forward in that direction. I have implemented a 2D camera, its always centered on the player. However, when i move towards the bounds of the world that the sprite is in it just keeps on going :( How to i sort it that it stops at the edge of the world and cant go beyond it? Cheers :) Below is the main game class using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace GamesCoursework_1 { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; // player variables Texture2D Ship; Vector2 Ship_Position; float Ship_Rotation = 0.0f; Vector2 Ship_Origin; Vector2 Ship_Velocity; const float tangentialVelocity = 4f; float friction = 0.05f; static Point CameraViewport = new Point(800, 800); Camera2d cam = new Camera2d((int)CameraViewport.X, (int)CameraViewport.Y); //Size of world static Point worldSize = new Point(1600, 1600); // Screen variables static Point worldCenter = new Point(worldSize.X / 2, worldSize.Y / 2); Rectangle playerBounds = new Rectangle(CameraViewport.X / 2, CameraViewport.Y / 2, worldSize.X - CameraViewport.X, worldSize.Y - CameraViewport.Y); Rectangle worldBounds = new Rectangle(0, 0, worldSize.X, worldSize.Y); Texture2D background; public Game1() { graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = CameraViewport.X; graphics.PreferredBackBufferHeight = CameraViewport.Y; Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); // TODO: use this.Content to load your game content here Ship = Content.Load<Texture2D>("Ship"); Ship_Origin.X = Ship.Width / 2; Ship_Origin.Y = Ship.Height / 2; background = Content.Load<Texture2D>("aus"); Ship_Position = new Vector2(worldCenter.X, worldCenter.Y); cam.Pos = Ship_Position; cam.Zoom = 1f; } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { // TODO: Unload any non ContentManager content here } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); // TODO: Add your update logic here Ship_Position = Ship_Velocity + Ship_Position; keyPressed(); base.Update(gameTime); } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); // TODO: Add your drawing code here spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend, null, null, null,null, cam.get_transformation(GraphicsDevice)); spriteBatch.Draw(background, Vector2.Zero, Color.White); spriteBatch.Draw(Ship, Ship_Position, Ship.Bounds, Color.White, Ship_Rotation, Ship_Origin, 1.0f, SpriteEffects.None, 0f); spriteBatch.End(); base.Draw(gameTime); } private void Ship_Move(Vector2 move) { Ship_Position += move; } private void keyPressed() { KeyboardState keyState; // Move right keyState = Keyboard.GetState(); if (keyState.IsKeyDown(Keys.Right)) { Ship_Rotation = Ship_Rotation + 0.1f; } if (keyState.IsKeyDown(Keys.Left)) { Ship_Rotation = Ship_Rotation - 0.1f; } if (keyState.IsKeyDown(Keys.Up)) { Ship_Velocity.X = (float)Math.Cos(Ship_Rotation) * tangentialVelocity; Ship_Velocity.Y = (float)Math.Sin(Ship_Rotation) * tangentialVelocity; if ((int)Ship_Position.Y < playerBounds.Bottom && (int)Ship_Position.Y > playerBounds.Top) cam._pos.Y = Ship_Position.Y; if ((int)Ship_Position.X > playerBounds.Left && (int)Ship_Position.X < playerBounds.Right) cam._pos.X = Ship_Position.X; //tried world bounds here if (!worldBounds.Contains(new Point((int)Ship_Position.X, (int)Ship_Position.Y))) Ship_Position -= new Vector2(0.0f, -tangentialVelocity * 2); if (!worldBounds.Contains(new Point((int)Ship_Position.X, (int)Ship_Position.Y))) Ship_Position -= new Vector2(0.0f, 2 * tangentialVelocity); } else if(Ship_Velocity != Vector2.Zero) { float i = Ship_Velocity.X; float j = Ship_Velocity.Y; Ship_Velocity.X = i -= friction * i; Ship_Velocity.Y = j -= friction * j; if ((int)Ship_Position.Y < playerBounds.Bottom && (int)Ship_Position.Y > playerBounds.Top) cam._pos.Y = Ship_Position.Y; if ((int)Ship_Position.X > playerBounds.Left && (int)Ship_Position.X < playerBounds.Right) cam._pos.X = Ship_Position.X; } if (keyState.IsKeyDown(Keys.Q)) { if (cam.Zoom < 2f) cam.Zoom += 0.05f; } if (keyState.IsKeyDown(Keys.A)) { if (cam.Zoom > 0.3f) cam.Zoom -= 0.05f; } } } } my 2d camera class using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; namespace GamesCoursework_1 { public class Camera2d { protected float _zoom; // Camera Zoom public Matrix _transform; // Matrix Transform public Vector2 _pos; // Camera Position protected float _rotation; // Camera Rotation public int _viewportWidth, _viewportHeight; // viewport size public Camera2d(int ViewportWidth, int ViewportHeight) { _zoom = 1.0f; _rotation = 0.0f; _pos = Vector2.Zero; _viewportWidth = ViewportWidth; _viewportHeight = ViewportHeight; } // Sets and gets zoom public float Zoom { get { return _zoom; } set { _zoom = value; if (_zoom < 0.1f) _zoom = 0.1f; } // Negative zoom will flip image } public float Rotation { get { return _rotation; } set { _rotation = value; } } // Auxiliary function to move the camera public void Move(Vector2 amount) { _pos += amount; } // Get set position public Vector2 Pos { get { return _pos; } set { _pos = value; } } public Matrix get_transformation(GraphicsDevice graphicsDevice) { _transform = // Thanks to o KB o for this solution Matrix.CreateTranslation(new Vector3(-_pos.X, -_pos.Y, 0)) * Matrix.CreateRotationZ(Rotation) * Matrix.CreateScale(new Vector3(Zoom, Zoom, 1)) * Matrix.CreateTranslation(new Vector3(_viewportWidth * 0.5f, _viewportHeight * 0.5f, 0)); return _transform; } } }

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