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jjenkov (13) [Avatar] Offline
#1
Chapter 3 discusses cyclic dependencies among other things.
In particular, the text shows how you can get around instantiating
objects which have cyclic dependencies in their constructors.

In my opinion, having cyclic dependencies in your constructors is
a design flaw. Any maintenance developer looking those two classes
is going to be rather puzzled about how to instantiate them, and
what their relationship is. If you have components with cyclic
dependencies I consider it better pratice to

1) Create an interface for the components with only the necessary methods exposed.

2) Have the extra methods (setter or setters) in the implementation classes that allow you to
wire up the cyclic dependency.

3) Delegate object creation to a factory. That way the wiring up is hidden from the public
and so are the methods for creating this wiring. They should not be exposed in
the components interfaces, but only be available to the factory.


Just my 2 cents on that topic. Otherwise another great chapter in what is to become
THE book on DI in my opinion smilie
dhanji.prasanna (37) [Avatar] Offline
#2
Re: Chapter 3 - Cyclic Dependencies in Constructors
Sure, I believe I mention as much--that it should only be applied in rare cases. Sometimes you cant help it as you are refactoring legacy code to use DI.

Thanks for the kind words.
jjenkov (13) [Avatar] Offline
#3
Re: Chapter 3 - Cyclic Dependencies in Constructors
Hmm... you do it seems, having looked at the text once more.