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Law of Demeter (LoD)

Another interesting object-oriented design guideline is called the LoD, or the principle of least knowledge.

It states that the less different parts of your system know about each other, the better. By limiting the amount of required knowledge, you make sure that different parts can evolve without incurring large adaptations to other parts.

The LoD can be summarized as follows:

• Each subsystem should only have limited knowledge of other subsystems that are closely related.
• Each subsystem should only talk to friends, usually not to strangers.
• Each subsystem should only talk to its close friends.

These rules are, of course, all in favor of a good functional decomposition and loose coupling, limiting the impact and cost ...