How many dependencies should be passed using a ctor?

Question

If I have class A which has a dependency on class B, then class B could be passed in to the ctor of class A.

What about if class B has a dependency on class C, does that mean class A should receive all required dependencies upon construction ?

It's all answered here :P http://stackoverflow.com/questions/871405/why-do-i-need-an-ioc-container-as-opposed-to-straightforward-di-code — Ruben Bartelink, Oct 18 '10 at 08:08

score 4 · Accepted Answer · answered Oct 16 '10 at 10:37

In general terms, Dependency Injection would suggest that your classes should have passed all dependencies in the constructor.

However, for your example, it seems to me that A depends on B and B depends on C. In other words, A only needs to have passed B in the constructor; because B will already be constructed using the C instance. In other words, if we wrote the code without a DI framework:

 C c = new C();
 B b = new B(c);
 A a = new A(b);

How many dependencies should be passed using a ctor?

1 Answers1