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• Factories, or Dependency Injection for object instantiation in WCF, when coding against an interface

  - by Saajid Ismail

  Hi I am writing a client/server application, where the client is a Windows Forms app, and the server is a WCF service hosted in a Windows Service. Note that I control both sides of the application. I am trying to implement the practice of coding against an interface: i.e. I have a Shared assembly which is referenced by the client application. This project contains my WCF ServiceContracts and interfaces which will be exposed to clients. I am trying to only expose interfaces to the clients, so that they are only dependant on a contract, not any specific implementation. One of the reasons for doing this is so that I can have my service implementation, and domain change at any time without having to recompile and redeploy the clients. The interfaces/contracts will in this case not change. I only need to recompile and redeploy my WCF service. The design issue I am facing now, is: on the client, how do I create new instances of objects, e.g. ICustomer, if the client doesn't know about the Customer concrete implementation? I need to create a new customer to be saved to the DB. Do I use dependency injection, or a Factory class to instantiate new objects, or should I just allow the client to create new instances of concrete implementations? I am not doing TDD, and I will typically only have one implementation of ICustomer or any other exposed interface.

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• Correctly use dependency injection

  - by Rune

  Me and two other colleagues are trying to understand how to best design a program. For example, I have an interface ISoda and multiple classes that implement that interface like Coke, Pepsi, DrPepper, etc.... My colleague is saying that it's best to put these items into a database like a key/value pair. For example: Key | Name -------------------------------------- Coke | my.namespace.Coke, MyAssembly Pepsi | my.namespace.Pepsi, MyAssembly DrPepper | my.namespace.DrPepper, MyAssembly ... then have XML configuration files that map the input to the correct key, query the database for the key, then create the object. I don't have any specific reasons, but I just feel that this is a bad design, but I don't know what to say or how to correctly argue against it. My second colleague is suggesting that we micro-manage each of these classes. So basically the input would go through a switch statement, something similiar to this: ISoda soda; switch (input) { case "Coke": soda = new Coke(); break; case "Pepsi": soda = new Pepsi(); break; case "DrPepper": soda = new DrPepper(); break; } This seems a little better to me, but I still think there is a better way to do it. I've been reading up on IoC containers the last few days and it seems like a good solution. However, I'm still very new to dependency injection and IoC containers, so I don't know how to correctly argue for it. Or maybe I'm the wrong one and there's a better way to do it? If so, can someone suggest a better method? What kind of arguments can I bring to the table to convince my colleagues to try another method? What are the pros/cons? Why should we do it one way? Unfortunately, my colleagues are very resistant to change so I'm trying to figure out how I can convince them.

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• dll injection using C

  - by AJINKYA

  hey i m trying to inject a dll into a process i.e lsass.exe to get hashes.Its a bit hacky but cant help its my project. I have a code of dll injection but in visual C++ it gives errors such as.. at TEXT("LoadLibraryA"))))----argument const wchar incompatible with LPCSTR at lpFuncAddr-----------argument type "LPVOID" incompatible with parameter type "LPTHREAD_START ROUTINE" CODE: BOOL InjectDLL(DWORD dwProcessId, LPCSTR lpszDLLPath) { HANDLE hProcess, hThread; LPVOID lpBaseAddr, lpFuncAddr; DWORD dwMemSize, dwExitCode; BOOL bSuccess = FALSE; HMODULE hUserDLL; //convert char to wchar char *lpszDLLPath = "hash.dll"; size_t origsize = strlen(orig) + 1; const size_t newsize = 100; size_t convertedChars = 0; wchar_t dllpath[newsize]; mbstowcs_s(&convertedChars, dllpath, origsize, orig, _TRUNCATE); if((hProcess = OpenProcess(PROCESS_CREATE_THREAD|PROCESS_QUERY_INFORMATION|PROCESS_VM_OPERATION |PROCESS_VM_WRITE|PROCESS_VM_READ, FALSE, dwProcessId))) { dwMemSize = wcslen(dllpath) + 1; if((lpBaseAddr = VirtualAllocEx(hProcess, NULL, dwMemSize, MEM_COMMIT, PAGE_READWRITE))) { if(WriteProcessMemory(hProcess, lpBaseAddr, lpszDLLPath, dwMemSize, NULL)) { if((hUserDLL = LoadLibrary(TEXT("kernel32.dll")))) { if((lpFuncAddr = GetProcAddress(hUserDLL, TEXT("LoadLibraryA")))) { if((hThread = CreateRemoteThread(hProcess, NULL, 0, lpFuncAddr, lpBaseAddr, 0, NULL))) { WaitForSingleObject(hThread, INFINITE); if(GetExitCodeThread(hThread, &dwExitCode)) { bSuccess = (dwExitCode != 0) ? TRUE : FALSE; } CloseHandle(hThread); } } FreeLibrary(hUserDLL); } } VirtualFreeEx(hProcess, lpBaseAddr, 0, MEM_RELEASE); } CloseHandle(hProcess); } return bSuccess; } int WINAPI WinMain(HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpszCmdLine, int nCmdShow) { if(InjectDLL(PROCESSID, "hash.dll")) { MessageBox(NULL, TEXT("DLL Injected!"), TEXT("DLL Injector"), MB_OK); }else { MessageBox(NULL, TEXT("Couldn't inject DLL"), TEXT("DLL Injector"), MB_OK | MB_ICONERROR); } return 0; } i m a beginner to dll and windows programming so will appreciate your help.

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• Dependency injection and factory

  - by legenden

  Trying to figure out how to best handle the following scenario: Assume a RequestContext class which has a dependency to an external service, such as: public class RequestContext : IRequestContext { private readonly ServiceFactory<IWeatherService> _weatherService; public RequestContext(ServiceFactory<IWeatherService> weatherService, UserLocation location, string query) { _weatherService = weatherService; ... What sort of dependency should I require in the class that will ultimately instantiate RequestContext? It could be ServiceFactory<IWeatherService>, but that doesn't seem right, or I could create an IRequestContextFactory for it along the lines of: public class RequestContextFactory : IRequestContextFactory { private readonly ServiceFactory<IWeatherService> _weatherService; public RequestContextFactory(ServiceFactory<IWeatherService> weatherService) { _weatherService = weatherService; } public RequestContext Create(UserLocation location, string query) { return new RequestContext(_weatherService, location, query); } } And then pass the IRequestContextFactory through constructor injection. This seems like a good way to do it, but the problem with this approach is that I think it hinders discoverability (devs must know about the factory and implement it, which is not really apparent). Is there a better/more discoverable way that I'm missing?

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• Dependency Injection for objects that require parameters

  - by Andrew

  All of our reports are created from object graphs that are translated from our domain objects. To enable this, we have a Translator class for each report, and have been using Dependency Injection for passing in dependencies. This worked great, and would yield nice classes structured like this: public class CheckTranslator : ICheckTranslator { public CheckTranslator (IEmployeeService empSvc , IPaycheckService paySvc) { _empSvc = empSvc; _paySvc = paySvc; } public Check CreateCheck() { //do the translation... } } However, in some cases the mapping has many different grouping options. As a result, the c-tor would turn into a mix of class dependencies and parameters. public class CheckTranslator : ICheckTranslator { public CheckTranslator (IEmployeeService empSvc , IPaycheckService paySvc , bool doTranslateStubData , bool doAttachLogo) { _empSvc = empSvc; _paySvc = paySvc; _doTranslateStubData = doTranslateStubData; _doAttachLogo = doAttachLogo; } public Check CreateCheck() { //do the translation... } } Now, we can still test it, but it no longer really works with an IoC container, at least in a clean fashion. Plus, we can no longer call the CreateCheck twice if the settings are different for each check. While I recognize it's a problem, I don't necessarily see the right solution. It seems kind of strange to create a Factory for each class ... or is this the best way?

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• Considerations when architecting an application using Dependency Injection

  - by Dan Bryant

  I've begun experimenting with dependency injection (in particular, MEF) for one of my projects, which has a number of different extensibility points. I'm starting to get a feel for what I can do with MEF, but I'd like to hear from others who have more experience with the technology. A few specific cases: My main use case at the moment is exposing various singleton-like services that my extensions make use of. My Framework assembly exposes service interfaces and my Engine assembly contains concrete implementations. This works well, but I may not want to allow all of my extensions to have access to all of my services. Is there a good way within MEF to limit which particular imports I allow a newly instantiated extension to resolve? This particular application has extension objects that I repeatedly instantiate. I can import multiple types of Controllers and Machines, which are instantiated in different combinations for a Project. I couldn't find a good way to do this with MEF, so I'm doing my own type discovery and instantiation. Is there a good way to do this within MEF or other DI frameworks? I welcome input on any other things to watch out for or surprising capabilities you've discovered that have changed the way you architect.

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• spring - constructor injection and overriding parent definition of nested bean

  - by mdma

  I've read the Spring 3 reference on inheriting bean definitions, but I'm confused about what is possible and not possible. For example, a bean that takes a collaborator bean, configured with the value 12 <bean name="beanService12" class="SomeSevice"> <constructor-arg index="0"> <bean name="beanBaseNested" class="SomeCollaborator"> <constructor-arg index="0" value="12"/> </bean> </constructor-arg> </bean> I'd then like to be able to create similar beans, with slightly different configured collaborators. Can I do something like <bean name="beanService13" parent="beanService12"> <constructor-arg index="0"> <bean> <constructor-arg index="0" value="13"/> </bean> </constructor> </bean> I'm not sure this is possible and, if it were, it feels a bit clunky. Is there a nicer way to override small parts of a large nested bean definition? It seems the child bean has to know quite a lot about the parent, e.g. constructor index. I'd prefer not to change the structure - the parent beans use collaborators to perform their function, but I can add properties and use property injection if that helps. This is a repeated pattern, would creating a custom schema help? Thanks for any advice!

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• Dependecy Injection with Massive ORM: dynamic trouble

  - by Sergi Papaseit

  I've started working on an MVC 3 project that needs data from an enormous existing database. My first idea was to go ahead and use EF 4.1 and create a bunch of POCO's to represent the tables I need, but I'm starting to think the mapping will get overly complicated as I only need some of the columns in some of the tables. (thanks to Steven for the clarification in the comments. So I thought I'd give Massive ORM a try. I normally use a Unit of Work implementation so I can keep everything nicely decoupled and can use Dependency Injection. This is part of what I have for Massive: public interface ISession { DynamicModel CreateTable<T>() where T : DynamicModel, new(); dynamic Single<T>(string where, params object[] args) where T : DynamicModel, new(); dynamic Single<T>(object key, string columns = "*") where T : DynamicModel, new(); // Some more methods supported by Massive here } And here's my implementation of the above interface: public class MassiveSession : ISession { public DynamicModel CreateTable<T>() where T : DynamicModel, new() { return new T(); } public dynamic Single<T>(string where, params object[] args) where T: DynamicModel, new() { var table = CreateTable<T>(); return table.Single(where, args); } public dynamic Single<T>(object key, string columns = "*") where T: DynamicModel, new() { var table = CreateTable<T>(); return table.Single(key, columns); } } The problem comes with the First(), Last() and FindBy() methods. Massive is based around a dynamic object called DynamicModel and doesn't define any of the above method; it handles them through a TryInvokeMethod() implementation overriden from DynamicObject instead: public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result) { } I'm at a loss on how to "interface" those methods in my ISession. How could my ISession provide support for First(), Last() and FindBy()? Put it another way, how can I use all of Massive's capabilities and still be able to decouple my classes from data access?

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• Unity 1.2 Dependency injection of internal types

  - by qvin

  I have a facade in a library that exposes some complex functionality through a simple interface. My question is how do I do dependency injection for the internal types used in the facade. Let's say my C# library code looks like - public class XYZfacade:IFacade { [Dependency] internal IType1 type1 { get; set; } [Dependency] internal IType2 type2 { get; set; } public string SomeFunction() { return type1.someString(); } } internal class TypeA { .... } internal class TypeB { .... } And my website code is like - IUnityContainer container = new UnityContainer(); container.RegisterType<IType1, TypeA>(); container.RegisterType<IType2, TypeB>(); container.RegisterType<IFacade, XYZFacade>(); ... ... IFacade facade = container.Resolve<IFacade>(); Here facade.SomeFunction() throws an exception because facade.type1 and facade.type2 are null. Any help is appreciated.

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• Dependency Injection into your Singleton

  - by Langali

  I have a singleton that has a spring injected Dao (simplified below): public class MyService<T> implements Service<T> { private final Map<String, T> objects; private static MyService instance; MyDao myDao; public void set MyDao(MyDao myDao) { this. myDao = myDao; } private MyService() { this.objects = Collections.synchronizedMap(new HashMap<String, T>()); // start a background thread that runs for ever } public static synchronized MyService getInstance() { if(instance == null) { instance = new MyService(); } return instance; } public void doSomething() { myDao.persist(objects); } } My spring config will probably look like this: <bean id="service" class="MyService" factory-method="getInstance"/> But this will instantiate the MyService during startup. Is there a programmatic way to do a dependency injection of MyDao into MyService, but not have spring manage the MyService? Basically I want to be able to do this from my code: MyService.getInstance().doSomething(); while having spring inject the MyDao for me.

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• Dependency injection in constructors

  - by andre

  Hello everyone. I'm starting a new project and setting up the base to work on. A few questions have risen and I'll probably be asking quite a few in here, hopefully I'll find some answers. First step is to handle dependencies for objects. I've decided to go with the dependency injection design pattern, to which I'm somewhat new, to handle all of this for the application. When actually coding it I came across a problem. If a class has multiple dependencies and you want to pass on multiple dependencies via the constructor (so that they cannot be changed after you instantiate the object). How do you do it without passing an array of dependencies, using call_user_func_array(), eval() or Reflection? This is what i'm looking for: <?php class DI { public function getClass($classname) { if(!$this->pool[$classname]) { # Load dependencies $deps = $this->loadDependencies($classname); # Here is where the magic should happen $instance = new $classname($dep1, $dep2, $dep3); # Add to pool $this->pool[$classname] = $instance; return $instance; } else { return $this->pool[$classname]; } } } Again, I would like to avoid the most costly methods to call the class. Any other suggestions?

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• Dependency injection in C++

  - by Yorgos Pagles

  This is also a question that I asked in a comment in one of Miško Hevery's google talks that was dealing with dependency injection but it got buried in the comments. I wonder how can the factory / builder step of wiring the dependencies together can work in C++. I.e. we have a class A that depends on B. The builder will allocate B in the heap, pass a pointer to B in A's constructor while also allocating in the heap and return a pointer to A. Who cleans up afterwards? Is it good to let the builder clean up after it's done? It seems to be the correct method since in the talk it says that the builder should setup objects that are expected to have the same lifetime or at least the dependencies have longer lifetime (I also have a question on that). What I mean in code: class builder { public: builder() : m_ClassA(NULL),m_ClassB(NULL) { } ~builder() { if (m_ClassB) { delete m_ClassB; } if (m_ClassA) { delete m_ClassA; } } ClassA *build() { m_ClassB = new class B; m_ClassA = new class A(m_ClassB); return m_ClassA; } }; Now if there is a dependency that is expected to last longer than the lifetime of the object we are injecting it into (say ClassC is that dependency) I understand that we should change the build method to something like: ClassA *builder::build(ClassC *classC) { m_ClassB = new class B; m_ClassA = new class A(m_ClassB, classC); return m_ClassA; } What is your preferred approach?

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• C++ and Dependency Injection in unit testing

  - by lhumongous

  Suppose I have a C++ class like so: class A { public: A() { } void SetNewB( const B& _b ) { m_B = _b; } private: B m_B; } In order to unit test something like this, I would have to break A's dependency on B. Since class A holds onto an actual object and not a pointer, I would have to refactor this code to take a pointer. Additionally, I would need to create a parent interface class for B so I can pass in my own fake of B when I test SetNewB. In this case, doesn't unit testing with dependency injection further complicate the existing code? If I make B a pointer, I'm now introducing heap allocation, and some piece of code is now responsible for cleaning it up (unless I use ref counted pointers). Additionally, if B is a rather trivial class with only a couple of member variables and functions, why introduce a whole new interface for it instead of just testing with an instance of B? I suppose you could make the argument that it would be easier to refactor A by using an interface. But are there some cases where two classes might need to be tightly coupled?

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• Proper structure for dependency injection (using Guice)

  - by David B.

  I would like some suggestions and feedback on the best way to structure dependency injection for a system with the structure described below. I'm using Guice and thus would prefer solutions centered around it's annotation-based declarations, not XML-heavy Spring-style configuration. Consider a set of similar objects, Ball, Box, and Tube, each dependent on a Logger, supplied via the constructor. (This might not be important, but all four classes happen to be singletons --- of the application, not Gang-of-Four, variety.) A ToyChest class is responsible for creating and managing the three shape objects. ToyChest itself is not dependent on Logger, aside from creating the shape objects which are. The ToyChest class is instantiated as an application singleton in a Main class. I'm confused about the best way to construct the shapes in ToyChest. I either (1) need access to a Guice Injector instance already attached to a Module binding Logger to an implementation or (2) need to create a new Injector attached to the right Module. (1) is accomplished by adding an @Inject Injector injectorfield to ToyChest, but this feels weird because ToyChest doesn't actually have any direct dependencies --- only those of the children it instantiates. For (2), I'm not sure how to pass in the appropriate Module. Am I on the right track? Is there a better way to structure this? The answers to this question mention passing in a Provider instead of using the Injector directly, but I'm not sure how that is supposed to work. EDIT: Perhaps a more simple question is: when using Guice, where is the proper place to construct the shapes objects? ToyChest will do some configuration with them, but I suppose they could be constructed elsewhere. ToyChest (as the container managing them), and not Main, just seems to me like the appropriate place to construct them.

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• DCI: How to implement Context with Dependency Injection?

  - by ciscoheat

  Most examples of a DCI Context are implemented as a Command pattern. When using Dependency Injection though, it's useful to have the dependencies injected in the constructor and send the parameters into the executing method. Compare the Command pattern class: public class SomeContext { private readonly SomeRole _someRole; private readonly IRepository<User> _userRepository; // Everything goes into the constructor for a true encapsuled command. public SomeContext(SomeRole someRole, IRepository<User> userRepository) { _someRole = someRole; _userRepository = userRepository; } public void Execute() { _someRole.DoStuff(_userRepository); } } With the Dependency injected class: public class SomeContext { private readonly IRepository<User> _userRepository; // Only what can be injected using the DI provider. public SomeContext(IRepository<User> userRepository) { _userRepository = userRepository; } // Parameters from the executing method public void Execute(SomeRole someRole) { someRole.DoStuff(_userRepository); } } The last one seems a bit nicer, but I've never seen it implemented like this so I'm curious if there are any things to consider.

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• Global State and Singletons Dependency injection

  - by Manu

  this is a problem i face lot of times when i am designing a new app i'll use a sample problem to explain this think i am writing simple game.so i want to hold a list of players. i have few options.. 1.use a static field in some class private static ArrayList<Player> players = new ArrayList<Integer>(); public Player getPlayer(int i){ return players.get(i); } but this a global state 2.or i can use a singleton class PlayerList{ private PlayerList instance; private PlayerList(){...} public PlayerList getInstance() { if(instance==null){ ... } return instance; } } but this is bad because it's a singleton 3.Dependency injection class Game { private PlayerList playerList; public Game(PlayerList list) { this.list = list; } public PlayerList getPlayerList() { return playerList; } } this seems good but it's not, if any object outside Game need to look at PlayerList (which is the usual case) i have to use one of the above methods to make the Game class available globally. so I just add another layer to the problem. didn't actually solve anything. what is the optimum solution ? (currently i use Singleton approach)

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• Dependency Injection: How to pass DB around?

  - by Stephane

  Edit: This is a conceptual question first and foremost. I can make applications work without knowing this, but I'm trying to learn the concept. I've seen lots of videos with related classes and that makes sense, but when it comes to classes wrapping around other classes, I can't seem to grasp where things should be instantiated/passed around. =-=-=-=-=-=-= Question: Let's say I have a simple page that loads data from a table, manipulates the result and displays it. Simple. I'm going to use '=' for instantiating a class and '-' for passing a class in using constructor injection. It seems to me that the database has to be passed from one end of the application to the other which doesn't seem right. Here's how I would do it if I wanted to separate concerns: index =>Controller =>Model Layer =>Database =>DAO->Database I have this rule in my head that says I'm not supposed to create objects inside other objects. So what do I do with the Database? Or even the Model for that matter? I'm obviously missing something so basic about this. I would love a simplified example so that I can move forward in my code. I feel really hamstrung by this.

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• How do I use constructor dependency injection to supply Models from a collection to their ViewModels

  - by GraemeF

  I'm using constructor dependency injection in my WPF application and I keep running into the following pattern, so would like to get other people's opinion on it and hear about alternative solutions. The goal is to wire up a hierarchy of ViewModels to a similar hierarchy of Models, so that the responsibility for presenting the information in each model lies with its own ViewModel implementation. (The pattern also crops up under other circumstances but MVVM should make for a good example.) Here's a simplified example. Given that I have a model that has a collection of further models: public interface IPerson { IEnumerable<IAddress> Addresses { get; } } public interface IAddress { } I would like to mirror this hierarchy in the ViewModels so that I can bind a ListBox (or whatever) to a collection in the Person ViewModel: public interface IPersonViewModel { ObservableCollection<IAddressViewModel> Addresses { get; } void Initialize(); } public interface IAddressViewModel { } The child ViewModel needs to present the information from the child Model, so it's injected via the constructor: public class AddressViewModel : IAddressViewModel { private readonly IAddress _address; public AddressViewModel(IAddress address) { _address = address; } } The question is, what is the best way to supply the child Model to the corresponding child ViewModel? The example is trivial, but in a typical real case the ViewModels have more dependencies - each of which has its own dependencies (and so on). I'm using Unity 1.2 (although I think the question is relevant across the other IoC containers), and I am using Caliburn's view strategies to automatically find and wire up the appropriate View to a ViewModel. Here is my current solution: The parent ViewModel needs to create a child ViewModel for each child Model, so it has a factory method added to its constructor which it uses during initialization: public class PersonViewModel : IPersonViewModel { private readonly Func<IAddress, IAddressViewModel> _addressViewModelFactory; private readonly IPerson _person; public PersonViewModel(IPerson person, Func<IAddress, IAddressViewModel> addressViewModelFactory) { _addressViewModelFactory = addressViewModelFactory; _person = person; Addresses = new ObservableCollection<IAddressViewModel>(); } public ObservableCollection<IAddressViewModel> Addresses { get; private set; } public void Initialize() { foreach (IAddress address in _person.Addresses) Addresses.Add(_addressViewModelFactory(address)); } } A factory method that satisfies the Func<IAddress, IAddressViewModel> interface is registered with the main UnityContainer. The factory method uses a child container to register the IAddress dependency that is required by the ViewModel and then resolves the child ViewModel: public class Factory { private readonly IUnityContainer _container; public Factory(IUnityContainer container) { _container = container; } public void RegisterStuff() { _container.RegisterInstance<Func<IAddress, IAddressViewModel>>(CreateAddressViewModel); } private IAddressViewModel CreateAddressViewModel(IAddress model) { IUnityContainer childContainer = _container.CreateChildContainer(); childContainer.RegisterInstance(model); return childContainer.Resolve<IAddressViewModel>(); } } Now, when the PersonViewModel is initialized, it loops through each Address in the Model and calls CreateAddressViewModel() (which was injected via the Func<IAddress, IAddressViewModel> argument). CreateAddressViewModel() creates a temporary child container and registers the IAddress model so that when it resolves the IAddressViewModel from the child container the AddressViewModel gets the correct instance injected via its constructor. This seems to be a good solution to me as the dependencies of the ViewModels are very clear and they are easily testable and unaware of the IoC container. On the other hand, performance is OK but not great as a lot of temporary child containers can be created. Also I end up with a lot of very similar factory methods. Is this the best way to inject the child Models into the child ViewModels with Unity? Is there a better (or faster) way to do it in other IoC containers, e.g. Autofac? How would this problem be tackled with MEF, given that it is not a traditional IoC container but is still used to compose objects?

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• How can I use "Dependency Injection" in simple php functions, and should I bother?

  - by Tchalvak

  I hear people talking about dependency injection and the benefit of it all the time, but I don't really understand it. I'm wondering if it's a solution to the "I pass database connections as arguments all the time" problem. I tried reading wikipedia's entry on it, but the example is written in Java so I don't solidly understand the difference it is trying to make clear. ( http://en.wikipedia.org/wiki/Dependency_injection ). I read this dependency-injection-in-php article ( http://www.potstuck.com/2009/01/08/php-dependency-injection/ ), and it seems like the objective is to not pass dependencies to an object directly, but to cordon off the creation of an object along with the creation of it's dependencies. I'm not sure how to apply that in a using php functions context, though. Additionally, is the following Dependency Injection, and should I bother trying to do dependency injection in a functional context? Version 1: (the kind of code that I create, but don't like, every day) function get_data_from_database($database_connection){ $data = $database_connection->query('blah'); return $data; } Version 2: (don't have to pass a database connection, but perhaps not dependency injection?) function get_database_connection(){ static $db_connection; if($db_connection){ return $db_connection; } else { // create db_connection ... } } function get_data_from_database(){ $conn = get_database_connection(); $data = $conn->query('blah'); return $data; } $data = get_data_from_database(); Version 3: (the creation of the "object"/data is separate, and the database code is still, so perhaps this would count as dependency injection?) function factory_of_data_set(){ static $db_connection; $data_set = null; $db_connection = get_database_connection(); $data_set = $db_connection->query('blah'); return $data_set; } $data = factory_of_data_set(); Anyone have a good resource or just insight that makes the method and benefit -crystal- clear?

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• Jboss AS 7 - Dependency Injection

  - by Nic Willemse

  Im attempting to make use of dependency injection in Jboss AS 7 and im having huge difficulties. I have setup a EAR which contains both a EJB jar and a war. The war contains a richfaces web app. Im attempting to inject an EJB from the ejb jar into a faces managed bean with the code below : public class UserController { @EJB(mappedName="UserService") private UserFacadeService userService; public String getService(){ if(userService == null){ however when i deploy jboss puts the error in the console : rolled back with failure message {"Services with missing/unavailable dependencies" => ["jboss.deployment.subunit.\"GoodByeJohnEAR.ear\".\"GoodByeJohnWeb-1.0-SNAPSHOT.war\".component.\"managed-bean.za.co.gbj.UserController\".START missing [ jboss.naming.context.java.module.GoodByeJohnEAR.\"GoodByeJohnWeb-1.0-SNAPSHOT\".\"env/za.co.gbj.UserController/userService\" ]","jboss.deployment.subunit.\"GoodByeJohnEAR.ear\".\"GoodByeJohnWeb-1.0-SNAPSHOT.war\".jndiDependencyService missing [ jboss.naming.context.java.module.GoodByeJohnEAR.\"GoodByeJohnWeb-1.0-SNAPSHOT\".\"env/za.co.gbj.UserController/userService\" ]","jboss.naming.context.java.module.GoodByeJohnEAR.\"GoodByeJohnWeb-1.0-SNAPSHOT\".\"env/za.co.gbj.UserController/userService\".jboss.deployment.subunit.\"GoodByeJohnEAR.ear\".\"GoodByeJohnWeb-1.0-SNAPSHOT.war\".module.GoodByeJohnEAR.\"GoodByeJohnWeb-1.0-SNAPSHOT\".2 missing [ jboss.naming.context.java.module.GoodByeJohnEAR.\"GoodByeJohnWeb-1.0-SNAPSHOT\".env/UserService ]"]} 09:03:50,576 INFO [org.jboss.as.server.deployment] (MSC service thread 1-8) Starting deployment of "GoodByeJohnEAR.ear" 09:03:50,670 INFO [org.jboss.as.server.deployment] (MSC service thread 1-3) Starting deployment of "GoodByeJohnWeb-1.0-SNAPSHOT.war" 09:03:50,670 INFO [org.jboss.as.server.deployment] (MSC service thread 1-8) Starting deployment of "GoodByeJohnEJB-1.0-SNAPSHOT.jar" 09:03:51,367 WARN [org.jboss.as.server.deployment.service-loader] (MSC service thread 1-2) Encountered invalid class name "com.sun.faces.vendor.Tomcat6InjectionProvider:org.apache.catalina.util.DefaultAnnotationProcessor" for service type "com.sun.faces.spi.injectionprovider" 09:03:51,367 WARN [org.jboss.as.server.deployment.service-loader] (MSC service thread 1-2) Encountered invalid class name "com.sun.faces.vendor.Jetty6InjectionProvider:org.mortbay.jetty.plus.annotation.InjectionCollection" for service type "com.sun.faces.spi.injectionprovider" 09:03:51,375 INFO [org.jboss.as.ejb3.deployment.processors.EjbJndiBindingsDeploymentUnitProcessor] (MSC service thread 1-8) JNDI bindings for session bean named UserFacadeBean in deployment unit subdeployment "GoodByeJohnEJB-1.0-SNAPSHOT.jar" of deployment "GoodByeJohnEAR.ear" are as follows: java:global/GoodByeJohnEAR/GoodByeJohnEJB-1.0-SNAPSHOT/UserFacadeBean!za.co.gbj.UserFacadeService java:app/GoodByeJohnEJB-1.0-SNAPSHOT/UserFacadeBean!za.co.gbj.UserFacadeService java:module/UserFacadeBean!za.co.gbj.UserFacadeService java:global/GoodByeJohnEAR/GoodByeJohnEJB-1.0-SNAPSHOT/UserFacadeBean java:app/GoodByeJohnEJB-1.0-SNAPSHOT/UserFacadeBean java:module/UserFacadeBean 09:03:51,406 INFO [org.jboss.as.ejb3.deployment.processors.EjbJndiBindingsDeploymentUnitProcessor] (MSC service thread 1-4) JNDI bindings for session bean named UserFacadeBean in deployment unit subdeployment "GoodByeJohnWeb-1.0-SNAPSHOT.war" of deployment "GoodByeJohnEAR.ear" are as follows: java:global/GoodByeJohnEAR/GoodByeJohnWeb-1.0-SNAPSHOT/UserFacadeBean!za.co.gbj.UserFacadeService java:app/GoodByeJohnWeb-1.0-SNAPSHOT/UserFacadeBean!za.co.gbj.UserFacadeService java:module/UserFacadeBean!za.co.gbj.UserFacadeService java:global/GoodByeJohnEAR/GoodByeJohnWeb-1.0-SNAPSHOT/UserFacadeBean java:app/GoodByeJohnWeb-1.0-SNAPSHOT/UserFacadeBean java:module/UserFacadeBean 09:03:51,577 INFO [org.jboss.as.controller] (DeploymentScanner-threads - 1) Service status report New missing/unsatisfied dependencies: service jboss.naming.context.java.module.GoodByeJohnEAR."GoodByeJohnWeb-1.0-SNAPSHOT".env/UserService (missing) service jboss.naming.context.java.module.GoodByeJohnEAR."GoodByeJohnWeb-1.0-SNAPSHOT"."env/za.co.gbj.UserController/userService" (missing) Please assist!

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• When should method overloads be refactored?

  - by Ben Heley

  When should code that looks like: DoThing(string foo, string bar); DoThing(string foo, string bar, int baz, bool qux); ... DoThing(string foo, string bar, int baz, bool qux, string more, string andMore); Be refactored into something that can be called like so: var doThing = new DoThing(foo, bar); doThing.more = value; doThing.andMore = otherValue; doThing.Go(); Or should it be refactored into something else entirely? In the particular case that inspired this question, it's a public interface for an XSLT templating DLL where we've had to add various flags (of various types) that can't be embedded into the string XML input.

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• Sort method versus OrderBy LINQ extension method

  - by nmarun

  I have a class Product with an Id and a Name as properties. There are multiple ways of getting a list of products to display in sorted/ordered fashion, say, by the Name of the product. The two I’m concerned about here are the Sort and the OrderBy extension method through LINQ and the difference between them. 1: public class Product 2: { 3: public int Id { get; set; } 4: public string Name { get; set; } 5: } Below is the list of products that I’ll be using and is defined somewhere in the Program.cs...(read more)

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• MAKE CROSS THREAD METHOD CALLS USING INVOKE METHOD OF THE CONTROL

  Cross threading is a phenomina normally happening in any of application debug session. Developer may not able to understand what's this all about. He may not actually coded for any such scenario like Threading. But this exception may raise especially in side a method where you are accessing any of the GUI control menthod. One natural scenaio will happen, once you are handling with FielSystemWatcher class. But here 1st I will create a sceanrio and then will give you 2 way resolution too.

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• Is dependency injection by hand a better alternative to composition and polymorphism?

  - by Drake Clarris

  First, I'm an entry level programmer; In fact, I'm finishing an A.S. degree with a final capstone project over the summer. In my new job, when there isn't some project for me to do (they're waiting to fill the team with more new hires), I've been given books to read and learn from while I wait - some textbooks, others not so much (like Code Complete). After going through these books, I've turned to the internet to learn as much as possible, and started learning about SOLID and DI (we talked some about Liskov's substitution principle, but not much else SOLID ideas). So as I've learned, I sat down to do to learn better, and began writing some code to utilize DI by hand (there are no DI frameworks on the development computers). Thing is, as I do it, I notice it feels familiar... and it seems like it is very much like work I've done in the past using composition of abstract classes using polymorphism. Am I missing a bigger picture here? Is there something about DI (at least by hand) that goes beyond that? I understand the possibility of having configurations not in code of some DI frameworks having some great benefits as far as changing things without having to recompile, but when doing it by hand, I'm not sure if it's any different than stated above... Some insight into this would be very helpful!

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• it is a good approach to implement dependency injection in a desktop app?

  - by luis_laurent

  Well, the thing is that I am just about to create a Desktop App (with .NET windows forms) And now I just wonder if it would be really a wise choise to use any IoC (StructureMap,Ninject,Spring .Net), I have used them before for Asp.Net web applications but what makes me doubt now is the fact that working with windows forms my business entities will persist when I navigate through tabs and unlike than web forms or mvc apps where it would be necesary to inject my business entity for every new request that is performed, I mean this because of the Asp.Net page life cycle where is performed the initialization and controls instantiation. Maybe I am misunderstanding the point of using an IoC, so please tell me what do you think would be a better choise?

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