From: Axel Etzold <AEtzold@...>
Date: 2008-05-24T21:52:46+09:00
Subject: Re: How to model something


-------- Original-Nachricht --------
> Datum: Sat, 24 May 2008 20:09:51 +0900
> Von: Tobias Weber <towb@gmx.net>
> An: ruby-talk@ruby-lang.org
> Betreff: How to model something

> Hi,
> my programm needs to store persons. They have a weight and a gender. You 
> are only allowed to ask males for their weight, females will throw 
> dishes/exceptions. There *is* a method to change someones gender.
> 
> I could have 'if gender' in every accessor or use the state pattern. But 
> that has no state, so I'm confused. I would have to access the variable 
> in the wrapper class.
> 
> The programm can also shoot people into space, in which case the 
> implementation of weight changes but the same restrictions apply.
> The proxy pattern will help here, probably by having weight first call 
> delegate.weight, and if that isn't NoMethodException multiplying with 
> gravity.
> 
> Any advice or implementations of similar problems I could look at?
> 
> (and in reality people are TV series with 6 genders and 5 other 
> attributes, and space is just but a remote place to store things)
> 
> -- 
>   Tobias Weber

Hi Tobias,

I'd use Struct ...


Best regards,

Axel 


-----------------------------------------------------------
Human=Struct.new(:name,:gender,:weight,:position)

def check_and_multiply(arg,default_value,factor)
	# return factor, if arg==default_value, else return 1
	if arg==default_value
		return factor
	else
		return 1
	end
end
class Human 
	def ask_for_weight(weight_loss_factor=0.5)
		if self.gender=='female'
			return "Don't ask me this!"
		else
			return self.weight*check_and_multiply(self.position,'space',weight_loss_factor)
		end
	end
	def change_sex
		temp=self.dup
		if self.gender=='male'
			temp.gender='female'
		end
		if self.gender=='female'
			temp.gender='male'
		end
		return temp
	end
	def change_position
		temp=self.dup
		if self.position=='earth'
			temp.gender='space'
		end
		if self.gender=='space'
			temp.gender='earth'
		end
		return temp
	end

end



man1=Human.new('John','male',75.0,'space')
man2=Human.new('James','male',75.0,'earth')
woman=Human.new('Mary','female',55.0)
p woman.ask_for_weight
p man1.ask_for_weight
p man2.ask_for_weight
p man2.change_sex.name

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