X-FeedAbuse: http://nntpfeed.proxad.net/abuse.pl feeded by 88.191.16.109 Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!news.dougwise.org!nntpfeed.proxad.net!nospam.fr.eu.org!talisker.lacave.net!lacave.net!not-for-mail From: Felipe Balbi Newsgroups: comp.lang.ruby Subject: Re: Making a simple parser Date: Tue, 19 Apr 2011 16:03:34 -0500 Organization: Service de news de lacave.net Lines: 86 Message-ID: References: <87adbac7061a00a72e282c160ed42414@ruby-forum.com> NNTP-Posting-Host: bristol.highgroove.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: Quoted-printable X-Trace: talisker.lacave.net 1303247044 79240 65.111.164.187 (19 Apr 2011 21:04:04 GMT) X-Complaints-To: abuse@lacave.net NNTP-Posting-Date: Tue, 19 Apr 2011 21:04:04 +0000 (UTC) In-Reply-To: X-Received-From: This message has been automatically forwarded from the ruby-talk mailing list by a gateway at comp.lang.ruby. If it is SPAM, it did not originate at comp.lang.ruby. Please report the original sender, and not us. Thanks! For more details about this gateway, please visit: http://blog.grayproductions.net/categories/the_gateway X-Mail-Count: 381874 X-Ml-Name: ruby-talk X-Rubymirror: Yes X-Ruby-Talk: Xref: x330-a1.tempe.blueboxinc.net comp.lang.ruby:3191 Hi, "Jes=C3=BAs Gabriel y Gal=C3=A1n" wrote in pos= t = #993452: > On Sat, Apr 16, 2011 at 9:52 PM, Felipe Balbi wrote:= >> >> @children.each { |child| >> def supported? >> >> input =3D InputFormat.new(ARGV[0]) >> input.parse >> >> As it turns out, this isn't working because AInputFormat will only >> inherit from InputFormat at the time I actually use it, am I right ? A= ny >> tips you guys could give me to achieve what I want ? (from several >> possible input formats generate one output format) > > The above doesn't work, because the @children inside the instance > method "parse" is not the same as the @children inside the class > method "self.inherited". You have to give access to the class instance > variable, and then use that one from the parse method (the you will aaa, you're right :-) Good point. > see the next problem): > > class InputFormat > class << self > attr_accessor :children > end > > def initialize(input) > @input =3D input > end > > def parse > self.class.children.each {|child| child.parse(@input) if > child.supported?(@input)} > end > > def self.inherited(child) > (@children ||=3D []) << child > end > end > > class AInputFormat < InputFormat > def supported? > # check if we can parse this type of file > end > > def parse > # parse and generate array of hashes in known format > end > end > > ruby-1.8.7-p334 :028 > input =3D InputFormat.new("test") > =3D> # > ruby-1.8.7-p334 :029 > input.parse > NoMethodError: undefined method `supported?' for AInputFormat:Class > from (irb):11:in `parse' > from (irb):11:in `each' > from (irb):11:in `parse' > from (irb):29 > > The next problem, as you see, is that you are defining instance > methods in the subclasses, but are calling them on the class. Maybe > the methods parse and supported? in the children could be class > methods, or maybe what you store in @children could be an instance of > the class. I'm not instantiating AInputFormat in any part of the code... so making = those class methods is the way to go for me :-) Thanks for the tip :-) -- balbi -- = Posted via http://www.ruby-forum.com/.=