0

I have an interface:

public interface IInterface
{
string Get(obj o);
}

and I have the 2 classes:

public class C1 : IInterface
{
string Get(obj o);
}

public class C2 : IInterface
{
string Get(obj o);
}

I'd like to send in o and then have Ninject determine which interface it is based on the property of o. Obj being something like:

public class obj
{
    public string Name {get;set;}
    public int Id {get;set;}
}

I'd like something that's like:

Bind<IInterface>().To<C1>.When(obj.Name == "C1");
Bind<IInterface>().To<C2>.When(obj.Name == "C2");

but I haven't worked with Ninject before. Any ideas?

shamp00
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user3328656
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  • I think you've messed up your example. How could you ever instanciate an `IInterface` if doing so requires accessing an instance of `IInterface`? You couldn't. Do you mean to pass in the `obj` with a `Name` property to a factory which then returns `IInterface`? – BatteryBackupUnit Sep 16 '14 at 16:28
  • could you please "fix" the question so that the Q/A will be valuable to later readers, too? Thanks. – BatteryBackupUnit Sep 17 '14 at 04:48

1 Answers1

1

I've been somewhat liberal with the interpretation of your question, because i think you've skipped some "thinking steps" and necessary information.

However, what I recommend is doing it like this:

public interface INamed
{
    string Name { get; }
}

public interface IFactory
{
    IInterface Create(INamed obj);
}

public class Factory : IFactory
{
    private readonly IResolutionRoot resolutionRoot;

    public Factory(IResolutionRoot resolutionRoot)
    {
        this.resolutionRoot = resolutionRoot;
    }

    public IInterface Create(INamed obj) 
    {
        return this.resolutionRoot.Get<IInterface>(obj.Name);
    }
}

Alternative: you could also use the ninject factory extension. Sadly enough it does not support named bindings by default, but you can customize it do so like documented here.

However to be perfectly frank i would rather go for manually implementing the factory, because it is more easily understandable. If i would be customizing the factory - which i have done - i would consider adding support for attributes (which specify how to handle a factory method parameter) instead of having to configure each .ToFactory() binding how it will interpret parameters.

BatteryBackupUnit
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  • Thanks! A friend of mine suggested the factory pattern as well. Could you clarify the IResolutionRoot portion of it? – user3328656 Sep 16 '14 at 22:15
  • ninject's kernel is implementing the `IKernel` interface which in turn is deriving from `IBindingRoot` and `IResolutionRoot`. `IBindingRoot` is used for creating bindings (`Bind().To()...`) and `IResolutionRoot` is used for retrieving/instantiating types. You do not need to `Bind`, it's already bound by ninject. The ninject factory extension for example is internally also using the `IResolutionRoot` to instantiate types. – BatteryBackupUnit Sep 17 '14 at 04:46