To me, the a->b->c->d->foo() example just tells me that this needs to be factored out into a routine somewhere. Putting it in a's class is not necessarily the right thing, perhaps it just needs to be in a function local to the module that uses 108 times (of course if those 108 uses are spread all over then it probably should be in a's class).

Choosing the correct class to put it in may be difficult. It may be useful to call x->b->c->d->foo() for lots of different xs that don't necessarily share a base class and adding in a mixin class to all those classes may not be not possible.

Many examples of LoD are really about removing accessors. I think it's better to replace a->mother->brother->child->foo() with a->cousin->foo(). Do not replace it with a->foo_the_cousin() because chances are you'll want to call other methods on the cousin and also because it's not much of a saving in terms of typing (in this case it's not a saving at all).

So my sugestion for a better LoD is Consider replacing chains of accessor methods with a single method

In reply to Re^2: The Pretty Good Idea of Demeter (Was: Definition of Law of Demeter) by fergal
in thread Are lvalue methods (as properties) a good idea? by jplindstrom

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