law of demeter

Explanation in plain English:

• Your method can call other methods in its class directly
• Your method can call methods on its own fields directly (but not on the fields' fields)
• When your method takes parameters, your method can call methods on those parameters directly.
• When your method creates local objects, that method can call methods on the local objects.

but

• One should not call methods on a global object (but it can be passed as a parameter ?)
• One should not have a chain of messages a.getB().getC().doSomething() in some class other than a's class.

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Here's an exact quote briefly summarizing the topic from a slide for auniversity course found on the web, maybe it'll help clarify thehistorical confusion on this page:Law of Demeter

• governs the communication structure within an object-oriented design
  • restricts message-sending statements in method implementations
  • only talk to your immediate friends
• message target can only be one of the following objects:
  1. the method's object itself (C++, Java, C#: this; Smalltalk: self, super; VB.NET: Me)
  2. an object that is an argument in the method's signature
  3. an object referred to by the object's attribute
  4. an object created by the method
  5. an object referred to by a global variable