Law of demeter

by Ismael Soares @rkmael

Law of Demeter

What’s it?The  Law  of  Demeter  (LoD)  or  principle  of  least  knowledge  is  a  design  guideline  for  developing  software  

(https://en.wikipedia.org/wiki/Law_of_Demeter)

The OriginThe  guideline  was  proposed  at  Northeastern  University  towards  the  end  of  1987

Demeter is not a man, is a Greek goddess!

It  is  so  named  for  its  origin  in  the  Demeter  Project,  an  adaptive  programming  and  aspect-­‐oriented  programming  effort.

It means a philosophy of bottom-up

LoD Principle:• Each  unit  should  have  only  limited  knowledge  about  other  units:  

only  units  "closely"  related  to  the  current  unit.  

• Each  unit  should  only  talk  to  its  friends;  don't  talk  to  strangers.  

• Only  talk  to  your  immediate  friends.

Advantages:• More  maintainable  

• More  adaptable  

• Less  dependence  

• Very  useful  in  layered  architecture  

Disadvantages:• More  code  

• In  some  cases,  this  can  add  noticeable  time  and  space  overhead  

Bad Example

Fonte: https://www.javacodegeeks.com/2012/06/demeter-law.html

Good Example

Obrigado@rkmael

rkmael@hotmail.com

rkmael.com