The [Law of Demeter][1] indicates that you should only speak to objects that you know about directly.  That is, do not perform method chaining to talk to other objects.  When you do so, you are establishing improper linkages with the intermediary objects, inappropriately [coupling][2] your code to other code.

That&#39;s bad.

The solution would be for the class you do know about to essentially expose simple wrappers that delegate the responsibility to the object it has the relationship with.

That&#39;s good.

But, that seems to result in the class having low [cohesion][3].  No longer is it simply responsible for precisely what it does, but it also has the delegates that in a sense, making the code less cohesive by duplicating portions of the interface of its related object.

That&#39;s bad.

Does it really result in lowering cohesion?  Is it the lesser of two evils?

Is this one of those gray areas of development, where you can debate where the line is, or are there strong, principled ways of making a decision of where to draw the line and what criteria you can use to make that decision?


  [1]: http://en.wikipedia.org/wiki/Law_of_Demeter
  [2]: http://en.wikipedia.org/wiki/Coupling_(computer_science)
  [3]: http://en.wikipedia.org/wiki/Cohesion_(computer_science)

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Coupling, Cohesion and the Law of Demeter