design patterns - Object graph or individual properties as method parameters? -


say have quite deep object graph, simplified example, this

class car {     engine engine { get; set; }     dashboard dashboard { get; set; }     ienumerable<wheel> wheels { get; set; } }  class engine {     pump fuelpump { get; set; }     motor startermotor { get; set; } }

and sake of example, instead of car having start() method, want have carstarter in charge of doing this. imaginine car can big, nested object graph , carstarter needs access couple of properties, of several levels deep. should pass car object carstarter, or properties important? of these overloads in simplified example?

class carstarter {     void start(car car) {         car.dashboard.lights.switchon();         car.engine.fuelpump.run();         car.engine.startermotor.start();     }      void start(dashboard dashboard, pump fuelpump, motor startermotor) {         dashboard.lights.switchon();         fuelpump.run();         startermotor.start();     } }

the former feels wrong requires carstarter have in depth knowledge structure of entire nested structure of car class , properties. it's opaque properties of car object need populated when passed carstarter in unit test.

the latter seems better option me, @ risk of ending many parameters.

we can create parameter object detailed here: http://sourcemaking.com/refactoring/introduce-parameter-object


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