From: Ehsanul Hoque <ehsanul_g3@...>
Date: 2009-11-17T18:39:12+09:00
Subject: Re: Meaning of '!(...'    EG: "myObject.parse!(argv)"   ..?

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>=20
> Sorry Ryan... I'm still not getting it :-(
>=20
> What is that exclamation mark doing? Could I substitute lets say a 'w'=20
> for the exclamation mark?
>=20
> opts.send(:parse!=2C argv)   =3D> opts.send(:parsew=2C argv)
> opts.send(:parse=2C argv)    =3D> opts.send(:parse=2C argv)
>=20
> If I can=2C then I understand it. There are in fact two different methods=
=20
> 'parsew' and 'parse'. But if thats true... then in my orginal code=20
> above=2C there wasn't a 'parse!' method defined.
>=20
> --=20
> Posted via http://www.ruby-forum.com/.
>=20

I think you've got it. Basically parse!=2C and I mean all of it including t=
he exclamation mark=2C is a method defined separately from parse. In your o=
ptions class=2C they might look like this:

class Options
def parse!(argv)
# parsing code
end
def parse(argv)
opts =3D self.dup
opts.parse!(argv)
end
end

The example implementation is just a common idiom in ruby where a method en=
ding in a "bang"=2C or exclamation point is a destructive method=2C alterin=
g the state of the object=2C whereas the non-bang version of the method act=
s on a duplicate object=2C so as to keep the actual object unaltered. There=
 is nothing special about the bang in how it is processed in ruby=2C it's j=
ust taken as part of the method name. So yes=2C you can just replace it wit=
h "w" or something. The reason for the bang is just ruby convention. If you=
 wanted=2C you could reverse the definitions=2C and it would work fine=2C b=
ut just be confusing (don't do that=2C go by convention).=20

Hope that's clear.

- Ehsan
 		 	   		 =20
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