Why does Ruby hang when I use method_missing on String to redirect to chars? [closed] - ruby

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When I implement this code:
class String
def method_missing(meth,*args, &block)
if self.chars.respond_to? meth
self.chars.send meth, *args, &block
else
super
end
end
def respond_to?(meth)
if self.chars.respond_to? meth
true
else
super
end
end
end
Ruby gets stuck on flatten. Even requiring another file internally calls flatten so it hangs there. I've even tried this:
class String
def method_missing(meth,*args, &block)
if meth.to_sym == :flatten
super
elsif self.chars.respond_to? meth
self.chars.send meth, *args, &block
else
super
end
end
def respond_to?(meth)
if meth.to_sym == :flatten
super
elsif self.chars.respond_to? meth
true
else
super
end
end
end
But the same results occur. What's happening internally to cause flatten to fail?
Here's the error output:
2.1.2 :003 > require 'mygem'
=> true
2.1.2 :004 > require 'pry'
^CIRB::Abort: abort then interrupt!
from /home/user/dev/MyGem/lib/mygem/string_method_missing.rb:17:in `call'
from /home/user/dev/MyGem/lib/mygem/string_method_missing.rb:17:in `respond_to?'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/requirement.rb:112:in `flatten'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/requirement.rb:112:in `initialize'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/requirement.rb:70:in `new'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/requirement.rb:70:in `default'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/dependency.rb:260:in `merge'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/specification.rb:1323:in `block in activate_dependencies'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/specification.rb:1306:in `each'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/specification.rb:1306:in `activate_dependencies'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/specification.rb:1288:in `activate'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems.rb:194:in `try_activate'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:132:in `rescue in require'
from /home/user/.rvm/rubies/ruby-2.1.2/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:144:in `require'
from (irb):4
from /home/user/.rvm/rubies/ruby-2.1.2/bin/irb:11:in `<main>'
It happens strictly for any Array of strings which gets flattened.
2.1.2 :005 > [1,2,3].flatten
=> [1, 2, 3]
2.1.2 :006 > ["1","2","3"].flatten
^CIRB::Abort: abort then interrupt!
from /home/user/dev/MyGem/lib/mygem/string_method_missing.rb:17:in `call'
from /home/user/dev/MyGem/lib/mygem/string_method_missing.rb:17:in `respond_to?'
from (irb):6:in `flatten'
from (irb):6
from /home/user/.rvm/rubies/ruby-2.1.2/bin/irb:11:in `<main>'
UPDATE
I've updated the code for the fixes recommended in the comments. The problem is still happening. I'm looking forward to the answer.
Flatten seems to work if I tell it how deep to go. So that seems to indicate an infinite loop on flattening the array on the string object. Example:
2.1.2 :013 > ["1","2","3"].flatten(0)
=> ["1", "2", "3"]
2.1.2 :021 > ["1","2","3"].flatten(8)
=> ["1", "2", "3"]
2.1.2 :022 > ["1","2","3"].flatten(9)
=> ["1", "2", "3"]
How can I avoid the infinite loop and still do this method_missing? It would help to know what test flatten calls on the inner object so I could define that in the string and avoid the loop.

Answer 1

There isn't an inbuilt cap on flatten. So redirecting everything to chars in String through method_missing creates an Array like object that will cause the flatten method to infinitely loop.
Add this, it is a working solution:
class Array
# To fix a bug that our method_missing creates
# we need to set a MAXIMUM for FLATTEN
alias_method :_old_flatten, :flatten
alias_method :_old_flatten!, :flatten!
def flatten(level = 99)
_old_flatten(level)
end
def flatten!(level = 99)
_old_flatten!(level)
end
end