MooTools setOptions() nullifies object references

I bumped up into a problem where the object references where resolved as object copies when I passed them to class instances. That might sound easy to resolve, but unfortunately I was already deep in code and it was difficult to see this. Therefore, here’s a little explanation for those who are facing the same frustrating issue.

Say, you have variable ‘a’ and you want to pass it to a MooTools class B instance during creation. In the easiest case you’d use new B({ myReference: a}) and trust on MooTools’ Class.setOptions() to minify the need of code lines. This is what you should do… well at least that’s what I did and in this case it was a mistake.

It turns out that Class.setOptions() merges it’s arguments to this.options and then takes copy of them via $merge(). That means that any variable references you pass to setOptions() will get copied to this.options and.. well, that’s it. See lines 1170-1173 in uncompressed version of MooTools 1.2:

var Options = new Class({
    setOptions: function(){
        this.options = $merge.run([this.options].extend(arguments));

That effectively nullifies the benefits of Class.setOptions() if you want to pass in variable references..

Here’s a longer example to clarify (use Firebug):

  // The most basic MooTools class that implements options
  // ref is a variable meant for pointing at given object
  // (won't do that, however)
  var B = new Class({
    Implements: Options,
    options: {
      ref: null
    },
    initialize: function(options) {
      this.setOptions(options);
    }
  });

  // Ok let's create an instance that we can pass to B
  // It's similar with all sorts of variables
  var A = new Class({
    initialize: function() {
      this.somevar = 'untouched';
    }
  });
  var a = new A();

  // Create an instance of B and give it somevar as reference
  var b = new B({ ref: a });

  // prints out "untouched" as should
  console.log(b.options.ref.somevar);

  // Let's change the variable (direct access, bad)
  a.somevar = "changed";

  // b's reference should still point to a, right?
  // In that case the following should print "changed",
  // but because our reference object was copied instead
  // of retaining reference to it, we just get "untouched"
  console.log(b.options.ref.somevar);

I don’t know why MooTools wants to make a copy of arguments in setOptions() – propably for performance reasons.

Viivi & Wagner strip scraper

I wrote this little script as a mental exercise and to prove the power of Python programming language. If anyone accepts the challenge, I’d like to see submissions in other programming langauges

For the foreigners: this is the best comic in Finland, so I hope you’ll get translations soon! It tells about the relationship of a woman and a pig (sic) reflecting the deepest shadows of Finnish social life.

"""
	Creats local mirror from Viivi & Wagner strips by fetching all of them from hs.fi.

	Will create downloaded strips as
		2004/1.1.2004.gif
		2004/2.1.2004.gif
		...
		until today

	Try this in C++!

	Motivation: No one has build Viivi & Wagner search engine with speech bubble OCR support
	and I desperately wanted to find "Kottarainen lentaa korvaan" strip for my gf.

	Time to complete: 20 min.

"""

__docformat__ = "epytext"
__author__ = "Mikko Ohtamaa"
__license__ = "BSD"
__copyright__ = "2008 Mikko Ohtamaa"

import os
import re
import urllib
from BeautifulSoup import BeautifulSoup

# 1.1.2004 start page
url = "http://www.hs.fi/viivijawagner/1073386660690"

# Loop until there is no longer next link
while True:
	stream = urllib.urlopen(url)
	html = stream.read()
	stream.close()
	soup = BeautifulSoup(html)

	# Parse strip date from contents
	date = None

	# Find strip date, which is next to a title
	h1 = soup.findAll(text="Viivi ja Wagner")
	# Should be present always
	date = h1[0].parent.parent.p.string

	print "Fetching " + date

	# Scrape strip
	strip = soup.findAll("div" , { "class" : "strip" })
	img = strip[0].img

	stream = urllib.urlopen(img["src"])
	data = stream.read()
	stream.close()

	# For each year, give a new folder to avoid file system stress
	# (lotsa files in a folder kill poor Gnome)
	day, month, year = date.split(".")
	folder = year

	if not os.path.exists(folder):
		os.mkdir(folder)	

	# Store contents
	fname = os.path.join(folder, date + ".gif")
	f = open(fname, "wb")
	f.write(data)
	f.close()

	# Find next url, it is a containing one img tag
	img = soup.findAll(alt="seuraava")
        if len(img) == 0:
             break
	a = img[0].parent
	url = a["href"]

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