Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

Inject Array of Interfaces in Ninject

Consider the following code.

public interface IFoo { }


public class Bar
{
    public Bar(IFoo[] foos) { }
}


public class MyModule : NinjectModule
{
    public override void Load()
    {
        Bind<IFoo[]>().ToConstant(new IFoo[0]);
        // ToConstant() is just an example
    }
}


public class Program
{
    private static void Main(string[] args)
    {
        var kernel = new StandardKernel(new MyModule());
        var bar = kernel.Get<Bar>();
    }
}

When I try to run the program I get the following exception.

Error activating IFoo
No matching bindings are available, and the type is not self-bindable.
Activation path:
2) Injection of dependency IFoo into parameter foos of constructor of type Bar
1) Request for Bar

How can I inject / bind to an array in Ninject?

Thanks for your time.

Edit:
My application imports data which is created by a third party component. The import process applies different kind of filters (e.g. implementations of different filter interfaces). The rules for filtering change quite often but are too complex to be done with pure configuration (and a master filter).

I want to make adding/editing filters as easy as possible. What I have is an assembly where all the filter implementations are located in. I tried to bind every filter interface to the following method (which provides an instance of every implementation of that filter type). Basically I want to avoid the need to change my Ninject module when I add/remove filter classes.

    private IEnumerable<TInterface> GetInterfaceImplementations<TInterface>(IContext context)
    {
        return GetType().Assembly.GetTypes()
            .Where(t => typeof (TInterface).IsAssignableFrom(t) && IsConcreteClass(t))
            .Select(t => Kernel.Get(t)).Cast<TInterface>();
    }

I am feeling a bit guilty in terms of bypassing the containers DI mechanism. Is this a bad practice? Is there a common practice to do such things?

Resolution:
I use a wrapper class as bsnote suggested.

like image 581
Julian Lettner Avatar asked Jun 23 '10 15:06

Julian Lettner


1 Answers

Ninject supports multi injection which would resolve your issue. https://github.com/ninject/ninject/wiki/Multi-injection

public interface IFoo { }
public class FooA : IFoo {}
public class FooB : IFoo {}

public class Bar
{
    //array injected will contain [ FooA, FooB ] 
    public Bar(IFoo[] foos) { }
}

public class MyModule : NinjectModule
{
    public override void Load()
    {
        Bind<IFoo>().To<FooA>();
        Bind<IFoo>().To<FooB>();
        //etc..
    }
}
like image 87
Reid Evans Avatar answered Oct 08 '22 19:10

Reid Evans