I'm registering a bunch of different implementations of the same interface without service key, then adding
container.Register<IMyInterface, ImplementationA>();
container.Register<IMyInterface, ImplementationB>();
container.RegisterMany<ImplementationC>(serviceKey: "myServiceKey");
public class ImplementationA: IMyInterface
{
}
public class ImplementationB: IMyInterface
{
}
public class ImplementationC: IMyInterface, IMyInterface2
{
}
Now, when I call to resolve all IMyInterface instances, I get ImplementationA, ImplementationB and ImplementationC
var iMyInterfaceImplementations = container.ResolveMany<IMyInterface>();
Assert.Equals(iMyInterfaceImplementations.Count() == 3);
if I provide the serviceKey, I get just ImplementationC
var iMyKeyedInterfaceImplementations = container.ResolveMany<IMyInterface>(serviceKey: "myServiceKey);
Assert.Equals(iMyKeyedInterfaceImplementations.Coud() == 1);
Is there any way to get all the non keyed implementations? So that if I called
container.ResolveMany(what to put here?)
I'd get ImplementationA, and ImplementationB, but Not ImplementationC.
The solution should be generic.. in the end I don't want to skip just ImplementationC but all possible registrations of IMyInterface that are not keyed. I already tried
container.ResolveMany<IMyInterface>(serviceKey: DefaultKey.Value);
but that returns me one single IMyInterface implementations, not the two I registered.
Here is the related doc https://github.com/dadhi/DryIoc/blob/master/docs/DryIoc.Docs/RegisterResolve.md#resolving-as-keyvaluepair-wrapper
What you need is:
var defaultItems = container.Resolve<KeyValuePair<DefaultKey, IMyInterface>[]>();
Related
I've an abstract class:
[Configuration]
public abstract class AbstractAddon : IAddon
{
private readonly object configuration;
public AbstractAddon(object configuration)
{
this.configuration = configuration;
}
}
And several implementation of this.
I create a binding by convention as:
public class AddonsModule : Ninject.Modules.NinjectModule
{
public override void Load()
{
this.Bind(b => b.FromAssembliesMatching("*")
.SelectAllClasses()
.InheritedFrom(typeof(UIExtensibility.AbstractAddon))
.BindAllBaseClasses()
.Configure(c => c.InSingletonScope())
);
this.Bind<object>().ToProvider<ConfigurationProvider>().WhenClassHas<UIExtensibility.ConfigurationAttribute>();
}
and ConfigurationProvider is:
private class ConfigurationProvider : IProvider<object>
{
public object Create(IContext context)
{
return "configuration settings";
}
//...
}
Inside the Create method of ConfigurationProvider I thought I might be allowed to access which is the concrete class which is being requested around.
Each concrete class have an attribute PluginInformation I need in order to provide the correct configuration object. However, I don't know how to know which is the concrete class NInject is creating at the moment of the Create method provider is performed. And then, I can't get the PluginInformation attribute I need to link it and provide the correct configuration object.
How could I get access to the concrete class NInject is requesting at the moment of the object provider is performed?
The trouble was that on the first level of the IContext context parameter information, there is only the information according the Type it's providing, in my case: object type.
However IContext comes with the complete parent and plan context. So, at the point of the Create method of the provider is performed, some braches of the resolution are solved, for example: AbstractAddon. Every resolved information is on 'Context' like IContext fields. Moreover, the future steps are on 'Plan' like IContext fields.
So, in order to get the concrete type (inherited classes of AbstractAddon), I need to read the next property: context.Request.ParentContext.Plan.Type.
I have a scenario , where my current interface looks like
public interface IMathematicalOperation
{
void AddInt();
}
After an year i expect the interface to be extended with AddFloat method and also expect 100 users already consuming this interface. When i extend the interface with a new method after an year i don't want these 100 classes to get changed.
So how can i tackle this situation ? Is there any design pattern available already to take care of this situation ?
Note: i understand that i can have a abstract class which implement this interface and make all the methods virtual , so that clients can inherit from this class rather than the interface and override the methods . When i add a new method only the abstract class will be changed and the clients who are interested in the method will override the behavior (minimize the change) .
Is there any other way of achieving the same result (like having a method named Add and based on certain condition it will do Float addition or Integer addition) ?
Edit 1:
The new method gets added to the interface also needs to be called automatically along with the existing methods(like chain of responsibility pattern).
There are at least two possible solution I can think of:
Derive your new interface from your old interface
public interface IMathematicalOperation
{
void AddInt();
}
public interface IFloatingPointMathematicalOperation : IMathematicalOperation
{
void AddFloat();
}
Have simply a parallel interface which contains the new method and have all classes which need the new interface derive from it
I'd suggest the second solution, since I don't understand why you would want an established interface to change.
I encountered a similar issue some time ago and found the best way was not to try and extend an existing interface, but to provide different versions of the interface with each new interface providing extra functionality. Over time I found that was not adding functionality on a regular basis, may once a year, so adding extra interfaces was never really an issue.
So, for example this is your first version of the interface:
public interface IMathematicalOperation
{
void AddInt();
}
This interface would then be implemented on a class like this:
public class MathematicalOperationImpl : IMathematicalOperation
{
public void AddInt()
{
}
}
Then when you need to add new functionality, i.e. create a version 2, you would create another interface with the same name, but with a "2" on the end:
public interface IMathematicalOperation2 : IMathematicalOperation
{
void AddFloat();
}
And the MathematicalOperationImpl would be extended to implement this new interface:
public class MathematicalOperationImpl : IMathematicalOperation, IMathematicalOperation2
{
public void AddInt()
{
}
public void AddFloat()
{
}
}
All of your new/future clients could start using the version 2 interface, but your existing clients would continue to work because they will only know about the first version of the interface.
The options provided are syntactically viable but then, as is obvious, they won't apply to any previous users.
A better option would be to use the Visitor pattern
The pattern is best understood when you think about the details of OO code
this.foo(); // is identical to
foo(this);
Remember that there is always a hidden 'this' parameter passed with every instance call.
What the visitor pattern attempts to do is generalize this behavior using Double dispatch
Let's take this a hair further
public interface MathematicalOperation
{
void addInt();
void accept(MathVisitor v);
}
public interface MathVisitor {
void visit(MathematicalOperation operation);
}
public class SquareVistor implements MathVisitor {
void visit(MathematicalOperation operation) {
operation.setValue(operation.getValue() * 2);
}
}
public abstract class AbstractMathematicalOperation implements MathematicalOperation {
public void accept(MathVisitor f) {
f.visit(this); // we are going to do 'f' on 'this'. Or think this.f();
}
}
public class MyMathOperation extends AbstractMathematicalOperation {
}
someMathOperation.visit(new SquareVisitor()); // is now functionally equivalent to
someMathOperation.square();
The best bet would be for you to roll-out your initial interface with a visitor requirements, then immediately roll-out an abstract subclass that gives this default implementation so it's cooked right in (As the above class is). Then everyone can just extend it. I think you will find this gives you the flexibility you need and leaves you will the ability to work with legacy classes.
I have a set of componentes registered to StructureMap. What should be the best way to resolve a component depending on the actual Tenant?
Small example:
There are two tenants, say, Yellow and Green.
I have an IValidator that has two implementations: YellowValidator and GreenValidator.
Say the application is MVC and that the tentant comes form the URL.
So, I just need the proper IValidator to be injected depending on the tenant.
I've seen many solutions for multi-tenant applications that deals only with multitenancy of data, normaly configuring different databases depending on the tenant. That involves only parameter passing. But this is the case where variation occurs in behavior, not in data. I want the IoC container to Resolve the right instance transparently.
EDIT: more info:
The IValidator interface have a simple method bool Validate(), but the implementation require some injection.
There are other custom validators, but they are used by both tenants.
There is a clear tentant strategy based on the URL. This means that each request can have a different tenant, and that a single application serves both tenants.
There are many ways to skin a cat. It's hard for me to guess the design of your application, so here is an idea. Things that come in mind are to hide validators behind a composite, to allow users of the IValidator interface to know nothing about having many implementations. Such composite can look like this:
public class ValidatorComposite : IValidator
{
private IEnumerable<IValidator> validators;
public ValidatorComposite(
IEnumerable<IValidator> validators)
{
this.validators = validators;
}
public bool Validate(object instance)
{
return this.validators.All(v => v.Validate(instance));
}
}
You can create multiple composites and register them by key where the key is the name of the tenant (but without keyed registrations is probably just as easy). Those composites can be wrapped in yet another composite that will delegate to the proper tenant-specific composite. Such a tenant-selecting composite could look like this:
public class TenantValidatorComposite : IValidator
{
private ITenantContext tenantContext;
private IValidator defaultValidator;
private IDictionary<string, IValidator> tenantValidators;
public ValidatorComposite(
ITenantContext tenantContext,
IValidator defaultValidator,
IDictionary<string, IValidator> tenantValidators)
{
this.tenantContext = tenantContext;
this.defaultValidator = defaultValidator;
this.tenantValidators = tenantValidators;
}
public bool Validate(object instance)
{
string name = this.tenantContext.CurrentTenant.Name;
return this.defaultValidator.Validate(instance) &&
this.tenantValidators[name].Validate(instance);
}
}
The ITenantContext is an abstraction that allows you to get the current tenant within the current context. You probably already have something like that in place, but I imagine an implementation to look something like this:
class UrlBasedTenantContext : ITenantContext
{
public Tenant Current
{
get
{
// Naive implementation.
if (HttpContext.Current.Request.Url.Contains("tenant1"))
{
return Tenant1;
}
return Tenant2;
}
}
}
Create a TenantValidatorComposite would be easy:
var defaultValidator = CompositeValidator(
GetAllDefaultValidators());
var tenantValidators = new Dictionary<string, IValidator>()
{
{ "tenant1", new CompositeValidator(GetValidatorsFor("tenant1")) },
{ "tenant2", new CompositeValidator(GetValidatorsFor("tenant2")) },
};
var tenantValidator = new TenantValidatorComposite(
new UrlBasedTenantContext(),
defaultValidator,
tenantValidators);
I hope this helps.
I just recently started using Ninject (v2.2.0.0) in my ASP.NET MVC 3 application. So far I'm thrilled with it, but I ran into a situation I can't seem to figure out.
What I'd like to do is bind an interface to concrete implementations and have Ninject be able to inject the concrete implementation into a constructor using a factory (that will also be registered with Ninject). The problem is that I'd like my constructor to reference the concrete type, not the interface.
Here is an example:
public class SomeInterfaceFactory<T> where T: ISomeInterface, new()
{
public T CreateInstance()
{
// Activation and initialization logic here
}
}
public interface ISomeInterface
{
}
public class SomeImplementationA : ISomeInterface
{
public string PropertyA { get; set; }
}
public class SomeImplementationB : ISomeInterface
{
public string PropertyB { get; set; }
}
public class Foo
{
public Foo(SomeImplementationA implA)
{
Console.WriteLine(implA.PropertyA);
}
}
public class Bar
{
public Bar(SomeImplementationB implB)
{
Console.WriteLine(implB.PropertyB);
}
}
Elsewhere, I'd like to bind using just the interface:
kernel.Bind<Foo>().ToSelf();
kernel.Bind<Bar>().ToSelf();
kernel.Bind(typeof(SomeInterfaceFactory<>)).ToSelf();
kernel.Bind<ISomeInterface>().To ...something that will create and use the factory
Then, when requesting an instance of Foo from Ninject, it would see that one of the constructors parameters implements a bound interface, fetch the factory, and instantiate the correct concrete type (SomeImplementationA) and pass it to Foo's constructor.
The reason behind this is that I will have many implementations of ISomeInterface and I'd prefer to avoid having to bind each one individually. Some of these implementations may not be known at compile time.
I tried using:
kernel.Bind<ISomeInterface>().ToProvider<SomeProvider>();
The provider retrieves the factory based on the requested service type then calls its CreateInstance method, returning the concrete type:
public class SomeProvider : Provider<ISomeInterface>
{
protected override ISomeInterface CreateInstance(IContext context)
{
var factory = context.Kernel.Get(typeof(SomeInterfaceFactory<>)
.MakeGenericType(context.Request.Service));
var method = factory.GetType().GetMethod("CreateInstance");
return (ISomeInterface)method.Invoke();
}
}
However, my provider was never invoked.
I'm curious if Ninject can support this situation and, if so, how I might go about solving this problem.
I hope this is enough information to explain my situation. Please let me know if I should elaborate further.
Thank you!
It seems you have misunderstood how ninject works. In case you create Foo it sees that it requires a SomeImplementationA and will try to create an instance for it. So you need to define a binding for SomeImplementationA and not for ISomeInterface.
Also most likely your implementation breaks the Dependency Inversion Princple because you rely upon concrete instances instead of abstractions.
The solution to register all similar types at once (and the prefered way to configure IoC containers) is to use configuration by conventions. See the Ninject.Extensions.Conventions extenstion.
I'm trying to find a method of passing a constructor argument to the constructors of child classes.
These objects are immutable so I'd prefer to use constructor arguments.
The issue I have encountered is that ConstructorArgument does not inherit to child instantiations and the following statements are not interchangeable:
_parsingProcessor = _kernel.Get<IParsingProcessor>(new ConstructorArgument("dataFilePath", dataFilePath);
and
_parsingProcessor = _kernel.Get<IParsingProcessor>(new Parameter("dataFilePath", dataFilePath, true);
So, how can get an inheritable ConstructorArgument and when does it makes sense, if ever, to new the Parameter class?
Yes, you can do this, but it's probably not what you really want. If the container is not actually responsible for instantiating its own dependencies, then its dependencies probably shouldn't be sharing its constructor arguments - it just doesn't make sense.
I'm pretty sure I know what you're trying to do, and the recommended approach is to create a unique binding specifically for your one container, and use the WhenInjectedInto conditional binding syntax, as in the example below:
public class Hello : IHello
{
private readonly string name;
public Hello(string name)
{
this.name = name;
}
public void SayHello()
{
Console.WriteLine("Hello, {0}!", name);
}
}
This is the class that takes a constructor argument which we want to modify, depending on who is asking for an IHello. Let's say it's this boring container class:
public class MyApp : IApp
{
private readonly IHello hello;
public MyApp(IHello hello)
{
this.hello = hello;
}
public virtual void Run()
{
hello.SayHello();
Console.ReadLine();
}
}
Now, here's how you do up the bindings:
public class MainModule : NinjectModule
{
public override void Load()
{
Bind<IApp>().To<MyApp>();
Bind<IHello>().To<Hello>()
.WithConstructorArgument("name", "Jim");
Bind<IHello>().To<Hello>()
.WhenInjectedInto<MyApp>()
.WithConstructorArgument("name", "Bob");
}
}
Basically all this binding is doing is saying the name should be "Jim" unless it's being requested by Hello, which in this case it is, so instead it will get the name "Bob".
If you are absolutely certain that you truly want cascading behaviour and understand that this is very dangerous and brittle, you can cheat using a method binding. Assuming that we've now added a name argument to the MyApp class for some unspecified purpose, the binding would be:
Bind<IHello>().ToMethod(ctx =>
ctx.Kernel.Get<Hello>(ctx.Request.ParentContext.Parameters
.OfType<ConstructorArgument>()
.Where(c => c.Name == "name")
.First()));
Please, please, make sure you are positive that this is what you want before doing it. It looks easy but it is also very likely to break during a simple refactoring, and 95% of the "customized dependency" scenarios I've seen can be addressed using the WhenInjectedInto binding instead.