Frogs design

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'''An OO model of frogs.''' This beautiful design appeared in the 2004 427 exam.
 
'''An OO model of frogs.''' This beautiful design appeared in the 2004 427 exam.
  
[[image:frogs.gif|900px]]
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[[image:frogs.gif]]
  
 
== Design notes ==
 
== Design notes ==
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* ''Toad''s eat ''AdultFrogs''.
 
* ''Toad''s eat ''AdultFrogs''.
  
== Design Critique ==
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== Criticisms ==
  
This design is perfect.  It cannot be faulted.
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* [[2009 frog design criticisms]]
  
== Broken heuristics ==
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* [[2010 frog design criticisms]]
 
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* [[Beware type switches]] - ''Frog'' phases: ''Egg'', ''Tadpole'', ''AdultFrog''.
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* [[Avoid "becomes"]] - ''Frog'' phases of life are modeled by inheritance: ''Egg'', ''Tadpole'', ''AdultFrog''
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* [[Beware value switches]] - ''Tadpole''
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* [[Avoid no-op overrides]] ("Design by Contract") - the derived class ''Egg'' overrides the base class's ''hop()'' and ''swim()'' methods with methods which does nothing.
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* [[One key abstraction]] - the ''Move'' interface contains more than one key abstraction. It contains methods to move such as ''hop()'' and ''swim()'', but it also contains a ''display()'' method which is a separate key abstraction.
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:''This is a good start, but needs more explanation of how the rules are broken here.  Also needs a note about this contribution on the discussion page. --[[User:Warwick Irwin|Wal]]''
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== "Feels Bad" ==
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* ''Toad'' is a subclass of ''AdultFrog''.
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* ''FrogBrain'' contains an array of ''Egg''
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:''Why do these things feel bad? --[[User:Warwick Irwin|Wal]]''
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Latest revision as of 04:31, 15 July 2010

An OO model of frogs. This beautiful design appeared in the 2004 427 exam.

Frogs.gif

Design notes

  • This design models the lifecycles of Frogs.
  • A Frog begins life as an Egg, grows into a Tadpole and then an AdultFrog.
  • A FrogBrain belongs to a Frog and manages its behaviour.
  • There is one Biologist, Igor, who sometimes moves Frogs around. Igor has been known to fry their legs in white wine.
  • Toads don’t have the same lifecycle as Frogs, but they look and act a lot like Frogs.
  • Toads eat AdultFrogs.

Criticisms

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