CODEWITHSUNDEEP
rubyclassmethods
luk3thomas
luk3thomas

Reputation: 2612

Ruby class method naming conflicts

Is it possible to use the method open on my Parser class? It seems that the method is conflicting with IO::open?

class Parser
    require 'nokogiri'

    def parse
        doc = open "someFile.html"
        # Get to parsin' ...
    end 

    def open str
        Nokogiri::HTML(open(str))
    end 
end 

parser = Parser.new
parser.parse

When I run the script I get this error:

$ ruby parser.rb
parser.rb:10: stack level too deep (SystemStackError)

I've tried a variety of things, but the only thing that seems to work is to rename Parser::open to something other than open, like docopen

I'm trying to understand how ruby works, so any further explanation beyond the answer is greatly appreciated!

Upvotes: 2

Views: 215

Answers (3)

unnu
unnu

Reputation: 754

open is a method on the module Kernel that is included in Object the parent class of all Ruby classes. What happens is that open(str) in

class Parser

  def open str
    Nokogiri::HTML(open(str))
  end

is calling your defined open method on Parser recursively. If you change your method to

  def open str
    Nokogiri::HTML(Kernel.open(str))
  end

you'll call the open method on Kernel as intended.

Upvotes: 2

Ismael
Ismael

Reputation: 16720

You are having a stack level too deep (SystemStackError) error because your method is beeing called recursively.

def open str
  Nokogiri::HTML(open(str)) # here you call this same method over and over again
end

This happens because the method you defined is more close in context so it's the one picked to be called.

You can just rename your method as you figured out or you can do something like this to explicit call it on one receiver that has the open method you want to use defined

def open str
  uri = URI.parse(str)
  Nokogiri::HTML(uri.open)
end

Upvotes: 2

Leo Correa
Leo Correa

Reputation: 19789

What seems to be happening is that 

def open str
  Nokogiri::HTML(open(str))
end

is in a recursive loop which just causes the SystemStackError making the stack level too deep.

What exactly are you trying to do with open(str)? When you changed the open to docopen, where exactly did you change it?

Upvotes: 2

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