DryIoc recursive dependency exception with Factory (Func<>)

Question

Hey I've switched over to DryIoc from Autofac. My code previously worked but now causes an exception "Recursive dependency is detected when resolving". (Code is simplified)

public class AFactory {
   public AFactory(Func<A> getA){ }
}

public class BFactory {
   public BFactory(Func<B> getB, AFactory factory){ }
}

public class A { 
   public A(IrrelevantService service, BFactory factory){ }
}

The actual code is complicated so assume that there is a reason that this code structure is necessary.

It's trying to resolve AFactory --> A --> BFactory --> AFactory and this is causing the issue. But since it's using a Func<> so it should be fine? (or at least it is in Autofac).

Is there a way to register this so that it doesn't throw this exception?

Could you elaborate? In my head I thought the container would try to resolve AFactory and would see "Func" and then stop (preventing recursion). Could you provide an example of how to write the code so it does use Func so I can understand better? — user8051386, Sep 02 '20 at 09:54
No, never mind me, I read it wrong. I'll delete the previous comment, it makes no sense. — Lasse V. Karlsen, Sep 02 '20 at 11:19

dadhi · Accepted Answer · 2020-09-02T11:33:38.153

Here is the reason from the Func wrapper docs:

By default, does not permit recursive dependency.

The fix is described in the doc below or in the later section.

Here are all possible fixes:

using System;
using DryIoc;
                    
public class Program
{
    public static void Main()
    {
        var c = new Container(
            //rules => rules.WithFuncAndLazyWithoutRegistration() // fix1: make everything lazy resolvable preventing the recursive dependency check!
        );
        
        c.Register<A>(
            //setup: Setup.With(asResolutionCall: true) // fix2: makes A a dynamically resolvable
        );
        c.Register<AFactory>();
        
        c.Register<B>();
        c.Register<BFactory>(
            setup: Setup.With(asResolutionCall: true) // fix3: makes BFactory a dynamically resolvable - the fix is here and not in B because the BFactory is already loops to AFactory and making B dynamic is not enough
        );
        
        c.Register<IrrelevantService>();
        
        var af = c.Resolve<AFactory>();
        Console.WriteLine(af);
    }
    
    public class AFactory {
       public AFactory(Func<A> getA){ }
    }

    public class BFactory {
       public BFactory(Func<B> getB, AFactory aFactory){ }
    }

    public class A { 
       public A(IrrelevantService service, BFactory bFactory){ }
    }
    
    public class B {}
    public class IrrelevantService {}
}

Thanks for the help. I ended up using Lazy (in the initializer of BFactory). I attempted using fix2 (and fix 3) and it succeeded in creating the objects, but then when I called getA() it threw the same exception. (might be an issue with my code). — user8051386, Sep 03 '20 at 06:18
hmm, basicaly this is a nice and DryIoc agnostic workaround, adding to the docs :) — dadhi, Sep 03 '20 at 11:38

DryIoc recursive dependency exception with Factory (Func<>)

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