LoD: calling components` components - allowed or not?

Question

Is it allowed to call components' components according to the Law of Demeter?

By component I mean an object

• which was "exclusively" injected into the container or was created in the container

• which has the same life cycle with it's container

For example, Brain is a component of a Dog:

partial class Dog
{
    private readonly IBrain brain;

    public Dog(IBrain brain)
    {
        this.brain = brain;
    }
}

---

Here is some information I found:

http://c2.com/cgi/wiki?LawOfDemeter

Your method can call methods on its own fields directly (but not on the fields' fields)

---

message target can only be one of the following objects:

... an object referred to by the object's attribute

http://www.ccs.neu.edu/research/demeter/demeter-method/LawOfDemeter/paper-boy/demeter.pdf

A method of an object should invoke only the methods of the following kinds of objects:

...

any objects it creates/instantiates

its direct component objects

---

And here is a case:

partial class Dog
{
    public void Command(string cmd)
    {
        var movement = brain.GetMemory().GetMovement(cmd);

        skeleton.ExecuteMovement(movement);
    }
}

Answer 1

Is it allowed to call components' components according to the Law of Demeter?

By definition this is not allowed since you should Only talk to your immediate friends.

In other words, the IBrain service should not expose its internal services through its interface (assuming that GetMemory() returns an IMemory service of some kind). Instead, the IBrain interface should either provide provide a method that allows retrieving the movement -or- the IMemory should be injected directly intoDog`.