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• Access modifiers - Property on business objects - getting and setting

  - by Mike

  Hi, I am using LINQ to SQL for the DataAccess layer. I have similar business objects to what is in the data access layer. I have got the dataprovider getting the message #23. On instantiation of the message, in the message constructor, it gets the MessageType and makes a new instance of MessageType class and fills in the MessageType information from the database. Therefore; I want this to get the Name of the MessageType of the Message. user.Messages[23].MessageType.Name I also want an administrator to set the MessageType user.Messages[23].MessageType = MessageTypes.LoadType(3); but I don't want the user to publicly set the MessageType.Name. But when I make a new MessageType instance, the access modifier for the Name property is public because I want to set that from an external class (my data access layer). I could change this to property to internal, so that my class can access it like a public variable, and not allow my other application access to modify it. This still doesn't feel right as it seems like a public property. Are public access modifiers in this situation bad? Any tips or suggestions would be appreciated. Thanks.

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• ObjectiveC - Releasing objects added as parameters

  - by NobleK

  Ok, here goes. Being a Java developer I'm still struggling with the memory management in ObjectiveC. I have all the basics covered, but once in a while I encounter a challenge. What I want to do is something which in Java would look like this: MyObject myObject = new MyObject(new MyParameterObject()); The constructor of MyObject class takes a parameter of type MyParameterObject which I initiate on-the-fly. In ObjectiveC I tried to do this using following code: MyObject *myObject = [[MyObject alloc] init:[[MyParameterObject alloc] init]]; However, running the Build and Analyze tool this gives me a "Potential leak of an object" warning for the MyParameter object which indeed occurs when I test it using Instruments. I do understand why this happens since I am taking ownership of the object with the alloc method and not relinquishing it, I just don't know the correct way of doing it. I tried using MyObject *myObject = [[MyObject alloc] init:[[[MyParameterObject alloc] init] autorelease]]; but then the Analyze tool told me that "Object sent -autorelease too many times". I could solve the issue by modifying the init method of MyParameterObject to say return [self autorelease]; in stead of just return self;. Analyze still warnes about a potential leak, but it doesn't actually occur. However I believe that this approach violates the convention for managing memory in ObjectiveC and I really want to do it the right way. Thanx in advance.

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• Accessing Web.config directly in ASP.NET MVC 1

  - by Neil T.

  I'm trying to implement integration testing in my ASP.NET MVC 1.0 solution. The technologies in use are LINQ-to-SQL, NUnit and WatiN. I recently discovered a pattern that will allow me to create a testing version of the database on the fly without modifying the development version of the database. I needed this behavior in order to run my user interface tests in WatiN that may modify the database. The plan is to modify the connection string in the Web.config file, and pass that new connection string to the DataContext constructor. This way, I don't have to add routes or modify my URLs in order to perform the integration testing. I've set up the project so that the test setup can modify the connection string to point to the test database when the tests are running. The connection string is stored in web.config. The problem I'm having is that when I try to run the tests, I get a NullReferenceException when trying to access the HTTPContext. From everything that I have read so far, the HTTPContext is only available within the context of a controller. Here is the code for the property that is supposed to give me the reference to the Web.config file: private System.Configuration.Configuration WebConfig { get { ExeConfigurationFileMap fileMap = new ExeConfigurationFileMap(); // NullReferenceException occurs on this line. fileMap.ExeConfigFilename = HttpContext.Current.Server.MapPath("~\\web.config"); System.Configuration.Configuration config = ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None); return config; } } Is there something that I am missing in order to make this work? Is there a better way to accomplish what I'm trying to achieve?

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• Mutual class instances in C++

  - by SepiDev

  Hi guys. What is the issue with this code? Here we have two files: classA.h and classB.h classA.h: #ifndef _class_a_h_ #define _class_a_h_ #include "classB.h" class B; //???? class A { public: A() { ptr_b = new B(); //???? } virtual ~A() { if(ptr_b) delete ptr_b; //???? num_a = 0; } int num_a; B* ptr_b; //???? }; #endif //_class_a_h_ classB.h: #ifndef _class_b_h_ #define _class_b_h_ #include "classA.h" class A; //???? class B { public: B() { ptr_a = new A(); //???? num_b = 0; } virtual ~B() { if(ptr_a) delete ptr_a; //???? } int num_b; A* ptr_a; //???? }; #endif //_class_b_h_ when I try to compile it, the compiler (g++) says: classB.h: In constructor ‘B::B()’: classB.h:12: error: invalid use of incomplete type ‘struct A’ classB.h:6: error: forward declaration of ‘struct A’ classB.h: In destructor ‘virtual B::~B()’: classB.h:16: warning: possible problem detected in invocation of delete operator: classB.h:16: warning: invalid use of incomplete type ‘struct A’ classB.h:6: warning: forward declaration of ‘struct A’ classB.h:16: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined.

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• How to create a generic C free function .

  - by nomemory

  I have some C structures related to a 'list' data structure. They look like this. struct nmlist_element_s { void *data; struct nmlist_element_s *next; }; typedef struct nmlist_element_s nmlist_element; struct nmlist_s { void (*destructor)(void *data); int (*cmp)(const void *e1, const void *e2); unsigned int size; nmlist_element *head; nmlist_element *tail; }; typedef struct nmlist_s nmlist; This way I can have different data types being hold in "nmlist_element-data" . The "constructor" (in terms of OOP) has the following signature: nmlist *nmlist_alloc(void (*destructor)(void *data)); Where "destructor" is specific function that de-allocated "data" (being hold by the nmlist_element). If I want to have a list containing integers as data, my "destructor" would like this: void int_destructor(void *data) { free((int*)data); } Still i find it rather "unfriendly" for me to write a destructor functions for every simple primitive data type. So is there a trick to write something like this ? (for primitives): void "x"_destructor(void *data, "x") { free(("x" *)data); } PS: I am not a macro fan myself, and in my short experience regarding C, i don't use them, unless necessary.

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• Class design when working with dataset

  - by MC

  If you have to retrieve data from a database and bring this dataset to the client, and then allow the user to manipulate the data in various ways before updating the database again, what is a good class design for this if the data tables will not have a 1:1 relationship with the class objects? Here are some I came up with: Just manipulate the DataSet itself on the client and then send it back to the database as is. This will work though obviously the code will be very dirty and not well-structured. Same as #1, but wrap the dataset code around classes. What I mean is that you may have a class that takes a dataset or a datatable in its constructor, and then provides public methods and properties to simplify the code. Inside these methods and properties it will be reading or manipulating the dataset. To update the database afterwards will be easy because you already have the updated dataset. Get rid of the dataset entirely on the client, convert to objects, then convert back to a dataset when needing to update the database. Is there any good resources where I can find information on this?

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• Immutable classes in C++

  - by ereOn

  Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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• How to implement jsf validator?

  - by Krishna

  HI, I want to know how to implement Validator in JSF. What is the advantages of declaring the validator-id. When it will be called in the life cycle?. I have implemented the following code. Please find out what is wrong in the code. I am not seeing it called anywhere in the life cycle. <?xml version="1.0"?> <!DOCTYPE faces-config PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN" "http://java.sun.com/dtd/web-facesconfig_1_1.dtd"> <faces-config> <lifecycle> <phase-listener>javabeat.net.jsf.JsfPhaseListener</phase-listener> </lifecycle> <validator> <validator-id>JsfValidator</validator-id> <validator-class>javabeat.net.jsf.JsfValidator</validator-class> </validator> <managed-bean> <managed-bean-name>jsfBean</managed-bean-name> <managed-bean-class>javabeat.net.beans.ManagedBean</managed-bean-class> <managed-bean-scope>request</managed-bean-scope> </managed-bean> <navigation-rule> <navigation-case> <from-outcome>success</from-outcome> <to-view-id>success.jsp</to-view-id> </navigation-case> </navigation-rule> </faces-config> public class JsfValidator implements Validator { public JsfValidator() { System.out.println("Inside JsfValidator Constructor"); } @Override public void validate(FacesContext facesContext, UIComponent uiComponent, Object object) throws ValidatorException { System.out.println("Inside Validator"); } }

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• Java Inheritance - Getting a Parameter from Parent Class

  - by Aaron

  I'm trying to take one parameter from the parent class of Car and add it to my array (carsParked), how can i do this? Parent Class public class Car { protected String regNo; //Car registration number protected String owner; //Name of the owner protected String carColor; /** Creates a Car object * @param rNo - registration number * @param own - name of the owner **/ public Car (String rNo, String own, String carColour) { regNo = rNo; owner = own; carColor = carColour; } /** @return The car registration number **/ public String getRegNo() { return regNo; } /** @return A String representation of the car details **/ public String getAsString() { return "Car: " + regNo + "\nColor: " + carColor; } public String getColor() { return carColor; } } Child Class public class Carpark extends Car { private String location; // Location of the Car Park private int capacity; // Capacity of the Car Park - how many cars it can hold private int carsIn; // Number of cars currently in the Car Park private String[] carsParked; /** Constructor for Carparks * @param loc - the Location of the Carpark * @param cap - the Capacity of the Carpark */ public Carpark (String locations, int room) { location = locations; capacity = room; } /** Records entry of a car into the car park */ public void driveIn() { carsIn = carsIn + 1; } /** Records the departure of a car from the car park */ public void driveOut() { carsIn = carsIn - 1; } /** Returns a String representation of information about the carpark */ public String getAsString() { return location + "\nCapacity: " + capacity + " Currently parked: " + carsIn + "\n*************************\n"; } }

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• Which design pattern is most appropriate?

  - by Anon

  Hello, I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?. Here is an example (for simplicity, let's say there are only two possible algorithms) ... class Foo { private: // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1); AlgorithmInterface* a; }; class AlgorithmInterface { public: virtual void DoSomething = 0; }; class Algorithm1 : public AlgorithmInterface { public: Algorithm1( int i ) : value(i) {} virtual void DoSomething(){ // Does something with int value }; int value; }; class Algorithm2 : public AlgorithmInterface { public: Algorithm2( bool b ) : value(b) {} virtual void DoSomething(){ // Do something with bool value }; bool value; };

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• SCJP Book, IO section: Is this a typo or is there a reason it would look like this?

  - by iamchuckb

  My question is about line 4, where the new PrintWriter is created with the constructor taking the FileWriter fw as a parameter. I don't understand the use of chaining the BufferedWriter bw to FileWriter if it isn't used later on in the actual writing. Can Java apply chaining in a way that bw still somehow affects the rest of the program? 16. try { 17. FileWriter fw = new FileWriter(test); 18. BufferedWriter bw = new BufferedWriter(fw, 1024); 19. PrintWriter out = new PrintWriter(fw); 20. out.println("<html><body><h1>"); 21. out.println(args[0]); 22. out.println("</h1></body></html>"); 23. out.close(); 24. bw.close(); 25. fw.close(); 26. }catch(IOException e) { 27. e.printStackTrace(); 28. } I think it is probably a typo and they meant to use bw as the parameter for PrintWriter out but like the title says, I'm new to this. Thanks to all in advance.

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• Thread Safety of C# List<T> for readers

  - by ILIA BROUDNO

  I am planning to create the list once in a static constructor and then have multiple instances of that class read it (and enumerate through it) concurrently without doing any locking. In this article http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx MS describes the issue of thread safety as follows: Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe. A List can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. The "Enumerating through a collection is intrinsically not a thread-safe procedure." Statement is what worries me. Does this mean that it is thread safe for readers only scenario, but as long as you do not use enumeration? Or is it safe for my scenario?

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• Make Errors: Missing Includes in C++ Script?

  - by Abs

  Hello all, I just got help in how to compile this script a few mintues ago on SO but I have managed to get errors. I am only a beginner in C++ and have no idea what the below erros means or how to fix it. This is the script in question. I have read the comments from some users suggesting they changed the #include parts but it seems to be exactly what the script has, see this comment. [root@localhost wkthumb]# qmake-qt4 && make g++ -c -pipe -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I/usr/lib/qt4/mkspecs/linux-g++ -I. -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include -I. -I. -I. -o main.o main.cpp main.cpp:5:20: error: QWebView: No such file or directory main.cpp:6:21: error: QWebFrame: No such file or directory main.cpp:8: error: expected constructor, destructor, or type conversion before ‘*’ token main.cpp:11: error: ‘QWebView’ has not been declared main.cpp: In function ‘void loadFinished(bool)’: main.cpp:18: error: ‘view’ was not declared in this scope main.cpp:18: error: ‘QWebSettings’ has not been declared main.cpp:19: error: ‘QWebSettings’ has not been declared main.cpp:20: error: ‘QWebSettings’ has not been declared main.cpp: In function ‘int main(int, char**)’: main.cpp:42: error: ‘view’ was not declared in this scope main.cpp:42: error: expected type-specifier before ‘QWebView’ main.cpp:42: error: expected `;' before ‘QWebView’ make: *** [main.o] Error 1 I have the web kit on my Fedora Core 10 machine: qt-4.5.3-9.fc10.i386 qt-devel-4.5.3-9.fc10.i386 Thanks all for any help

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• Difficulty porting raw PCM output code from Java to Android AudioTrack API.

  - by IndigoParadox

  I'm attempting to port an application that plays chiptunes (NSF, SPC, etc) music files from Java SE to Android. The Android API seems to lack the javax multimedia classes that this application uses to output raw PCM audio. The closest analog I've found in the API is AudioTrack and so I've been wrestling with that. However, when I try to run one of my sample music files through my port-in-progress, all I get back is static. My suspicion is that it's the AudioTrack I've setup which is at fault. I've tried various different constructors but it all just outputs static in the end. The DataLine setup in the original code is something like: AudioFormat audioFormat = new AudioFormat( AudioFormat.Encoding.PCM_SIGNED, 44100, 16, 2, 4, 44100, true ); DataLine.Info lineInfo = new DataLine.Info( SourceDataLine.class, audioFormat ); DataLine line = (SourceDataLine)AudioSystem.getLine( lineInfo ); The constructor I'm using right now is: AudioTrack = new AudioTrack( AudioManager.STREAM_MUSIC, 44100, AudioFormat.CHANNEL_CONFIGURATION_STEREO, AudioFormat.ENCODING_PCM_16BIT, AudioTrack.getMinBufferSize( 44100, AudioFormat.CHANNEL_CONFIGURATION_STEREO, AudioFormat.ENCODING_PCM_16BIT ), AudioTrack.MODE_STREAM ); I've replaced constants and variables in those so they make sense as concisely as possible, but my basic question is if there are any obvious problems in the assumptions I made when going from one format to the other.

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• boost::filesystem - how to create a boost path from a windows path string on posix plattforms?

  - by VolkA

  I'm reading path names from a database which are stored as relative paths in Windows format, and try to create a boost::filesystem::path from them on a Unix system. What happens is that the constructor call interprets the whole string as the filename. I need the path to be converted to a correct Posix path as it will be used locally. I didn't find any conversion functions in the boost::filesystem reference, nor through google. Am I just blind, is there an obvious solution? If not, how would you do this? Example: std::string win_path("foo\\bar\\asdf.xml"); std::string posix_path("foo/bar/asdf.xml"); // loops just once, as part is the whole win_path interpreted as a filename boost::filesystem::path boost_path(win_path); BOOST_FOREACH(boost::filesystem::path part, boost_path) { std::cout << part << std::endl; } // prints each path component separately boost::filesystem::path boost_path_posix(posix_path); BOOST_FOREACH(boost::filesystem::path part, boost_path_posix) { std::cout << part << std::endl; }

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• Intermittent Issue Writing to Google Appengine Datastore

  - by user242153

  Hi, I have a functioning app and recently have had intermittent problems writing to the datastore. I did not make any relevant code changes, however in the last few days my attempts to write to the datastore sometimes work and sometimes don't. I am trying to save an object that is in a many to one relationship with an existing persisted parent. So, the logic works like this: 1) Parent pulled from the datastore 2) Child created / instantiated using constructor 3) Parent.addSingleChild(child); // the "addSingleChild" method just adds the object argument to the collection of children 4) child.setParent(Parent); // sets the Parent object to the parent field I am using transactions as explained in the documentation ending with "finally {if (tx.isActive()) {tx.rollback(); } }" When the servlet is called, the parent is called from the datastore and the child object is created and added to the many to one mapping to the pre-existing parent. The child should automatically be persisted, since the parent is already persistent, and the child is added to the collection of children that map to the parent. And it worked this way in the past. However, to be sure, i did add a pm.makePersistent(child). Doesn't seem to help, still have the intermittent problem. Any suggestions would be appreciated, and if you need to see the actual code I can post. Thanks

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• android: consume key press, bypassing framework processing

  - by user360024

  What I want android to do: when user presses a single key, have the view respond, but do so without opening a text area and displaying the character associated with the key that was pressed, and without requiring that the Enter key be pressed, and without requiring that the user press Esc to make the text area go away. For example, when user presses "u" (and doesn't press Enter), that means "undo the last action", so the controller and model immediately undo the last action, then the view does an invalidate() and user sees that their last action has been undone. In other words the "u" key press should be silently processed, such that the only visual result is that user's last action has been undone. I've implemented OnKeyListener and provided an onKey() method: the class: public class MyGameView extends View implements OnKeyListener{ in the constructor: //2010jun06, phj: With onKey(), helps let this View consume key presses // before the framework gets a chance to consume the key press. setOnKeyListener((View.OnKeyListener)this); the onKey() method: public boolean onKey(View v, int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_R) { Log.d("BWA", "In onKey received keycode associated with R."); } return true; // meaning the event (key press) has been consumed, so // the framework should not handle this event. } but when user presses "u" key on the emulator keypad, a textarea is opened at the bottom of the screen, the "u" charater is displayed there, and the onKey() method doesn't execute until user presses the Enter key. Is there a way to make android do what I want? Thanks,

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• ASP.NEt MVC 2 application error on IIS7 works fine on local machine

  - by aspCoolguy

  My ASP.NET MVC2 application is developed using 1. VS 2010 2. Linq To SQL for Models Here is Call controller code: namespace CallTrackMVC.Controllers { public class CallController : Controller { private CallTrackRepository repository; public CallController():this(new CallTrackRepository()) { } public CallController(CallTrackRepository newRepository) { repository = newRepository; } } } Error on IIS7 when browsing the Call Create page is NullReferenceException: Object reference not set to an instance of an object.] CallTrackMVC.Models.ExecOfficeDataContext..ctor() in C:\ClearCase\rartadi_view\STS_Dev_TEST\CallTrackMVC\Models\ExecOffice.designer.cs:71 CallTrackMVC.Controllers.CallController..ctor() in C:\ClearCase\rartadi_view\STS_Dev_TEST\CallTrackMVC\Controllers\CallController.cs:16 [TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +117 System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +247 System.Activator.CreateInstance(Type type, Boolean nonPublic) +106 System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +102 [InvalidOperationException: **An error occurred when trying to create a controller of type 'CallTrackMVC.Controllers.CallController'. Make sure that the controller has a parameterless public constructor.**] System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +541 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +85 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +165 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +80 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +389 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +371 Code in Global.asax is protected void Application_Start() { AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes); } Any suggestion would be a great help.

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• Serializing Configurations for a Dependency Injection / Inversion of Control

  - by Joshua Starner

  I've been researching Dependency Injection and Inversion of Control practices lately in an effort to improve the architecture of our application framework and I can't seem to find a good answer to this question. It's very likely that I have my terminology confused, mixed up, or that I'm just naive to the concept right now, so any links or clarification would be appreciated. Many examples of DI and IoC containers don't illustrate how the container will connect things together when you have a "library" of possible "plugins", or how to "serialize" a given configuration. (From what I've read about MEF, having multiple declarations of [Export] for the same type will not work if your object only requires 1 [Import]). Maybe that's a different pattern or I'm blinded by my current way of thinking. Here's some code for an example reference: public abstract class Engine { } public class FastEngine : Engine { } public class MediumEngine : Engine { } public class SlowEngine : Engine { } public class Car { public Car(Engine e) { engine = e; } private Engine engine; } This post talks about "Fine-grained context" where 2 instances of the same object need different implementations of the "Engine" class: http://stackoverflow.com/questions/2176833/ioc-resolve-vs-constructor-injection Is there a good framework that helps you configure or serialize a configuration to achieve something like this without hard coding it or hand-rolling the code to do this? public class Application { public void Go() { Car c1 = new Car(new FastEngine()); Car c2 = new Car(new SlowEngine()); } } Sample XML: <XML> <Cars> <Car name="c1" engine="FastEngine" /> <Car name="c2" engine="SlowEngine" /> </Cars> </XML>

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• Flash compiler error 1061: Call to a possibly undefined method run... but run exists!

  - by Zane Geiger

  So I've been working on making a game in Processing but I think Flash would be a better way to get more people playing it, so I've decided to learn Flash. The problem is that I keep getting really stupid errors on incredibly simple things. For instance, I want to make a 'Block' object to use in a platform game. So I make a new .as file, name it Block.as, and define the Block class within it like so: package { public class Block { public function Block() { // constructor code } public function run() { } } } I don't want to add the code yet, I just want to ensure that this works. So in my main timeline code, I try to create an instance of the Block object and execute its run method: var block1:Block = new Block(); block1.run(); Every time it gives me this inane error: Scene 1, Layer 'Layer 1', Frame 1, Line 2 1061: Call to a possibly undefined method run through a reference with static type Block. What undefined method!? It's defined RIGHT THERE in Block.as. The class file is even in the same folder and everything. I'm getting REALLY annoyed at how poorly Flash handles such a ridiculously simple project. Does anyone know why Flash hates me?

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• Java - How to declare table[i][j] elements as instance variables?

  - by JDelage

  All, I am trying to code a Connect4 game. For this, I have created a P4Game class and a P4Board class which represents the i X j dimensions of the Connect4 board. In P4Game, I have the following: public class P4Game{ //INSTANCE VARIABLES private int nbLines; private int nbColumns; private P4Board [][] position; //CONSTRUCTOR public P4Game(int nbLines, int nbColumns){ this.nbColumns = nbColumns; this.nbLines = nbLines; P4Board [][] position = new P4Board [nbLines][nbColumns]; //Creates the table to receive the instances of the P4Board object.*/ for (int i=0; i<nbLines; i++){ for (int j=0; j<nbColumns; j++){ this.position[i][j] = new P4Board(i,j); //Meant to create each object at (line=i, column=j) } } } This causes a NullPointerException in the nested loops where I mention this.position[i][j]. I reference those objects in other methods of this class so I need them to be instance variables. I suppose the exception is due to the fact that I have not listed the table element position[i][j] as an instance variable at the beginning of the class. my question to people here is (1) is my assumption correct, and if so (2) what would be the syntax to declare instance variables of this form? Thank you all for your help with what I realize is a very basic question. Hopefully it will also benefit other newbies. Cheers, JDelage

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• Threadsafe way of exposing keySet()

  - by Jake

  This must be a fairly common occurrence where I have a map and wish to thread-safely expose its key set: public MyClass { Map<String,String> map = // ... public final Set<String> keys() { // returns key set } } Now, if my "map" is not thread-safe, this is not safe: public final Set<String> keys() { return map.keySet(); } And neither is: public final Set<String> keys() { return Collections.unmodifiableSet(map.keySet()); } So I need to create a copy, such as: public final Set<String> keys() { return new HashSet(map.keySet()); } However, this doesn't seem safe either because that constructor traverses the elements of the parameter and add()s them. So while this copying is going on, a ConcurrentModificationException can happen. So then: public final Set<String> keys() { synchronized(map) { return new HashSet(map.keySet()); } } seems like the solution. Does this look right?

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• Usage Rails 3.0 beta 3 without ActiveRecord ORM

  - by Anton

  Hi everybody! Just installed Rails 3.0 beta 3 in Windows 7. And started playing with some easy examples class SignupController < ApplicationController def index @user = User.new(params[:user]) if method.post? and @user.save redirect_to :root end end end class User def initialize(params = {}) @email = params[:email] @passw = params[:password] end def save end end <div align="center"> <% form_for :user do |form| %> <%= form.label :email %> <%= form.text_field :email %><br /> <%= form.label :password %> <%= form.text_field :password %><br /> <%= form.submit :Register! %> <% end %> </div> When I go to /signup I'm getting this error ArgumentError in SignupController#index wrong number of arguments(0 for 1) Is there a problem with constructor or what's wrong?Please, need your help!

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• Generic cast type to primitive.

  - by Nix

  Is there a way to do the below? Imagine a generic result wrapper class. Where you have a type and an associated error list. When there is no result to return to the user we will use boolean to indicate success failure. I want to create a constructor that takes in an error list, and if the list is null or count 0, AND the type is a bool/Boolean i want to set it to true.... Seemingly simple, but amazingly not possible. public class Result<T>{ private T valueObject { get;set;} private List<Error> errors{ get;set;} public Result(T valueObj, List<Error> errorList){ this.valueObject = valueObj; this.errors = errorList; } public Result(List<Error> errors) { this.valueObject = default(ReturnType); if (valueObject is Boolean) { //Wont work compile //(valueObject as Boolean) = ((errors == null) || errors.Count == 0); //Compiles but detaches reference //bool temp = ((bool)(valueObject as object)) ; //temp = ((errors == null) || errors.Count == 0); } this.errors = errors; } } } Am I missing something simple? And in general I would prefer to do it without reflection.

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• How to enforce users to create objects of class derived from mine with "new" only?

  - by sharptooth

  To implement reference counting we use an IUnknown-like interface and a smart pointer template class. The interface has implementation for all the reference-count methods, including Release(): void IUnknownLike::Release() { if( --refCount == 0 ) { delete this; } } The smart pointer template class has a copy constructor and an assignment operator both accepting raw pointers. So users can do the following: class Class : public IUnknownLike { }; void someFunction( CSmartPointer<Class> object ); //whatever function Class object; someFunction( &object ); and the program runs into undefined behavior - the object is created with reference count zero, the smart pointer is constructed and bumps it to one, then the function returns, smart pointer is destroyed, calls Release() which leads to delete of a stack-allocated variable. Users can as well do the following: struct COuter { //whatever else; Class inner;// IUnknownLike descendant }; COuter object; somefunction( &object.Inner ); and again an object not created with new is deleted. Undefined behavior at its best. Is there any way to change the IUnknownLike interface so that the user is forced to use new for creating all objects derived from IUnknownLike - both directly derived and indirectly derived (with classes in between the most derived and the base)?

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