Ruby: Convert String to Boolean

string_ext.rb

class String
  def to_bool
    return true   if self == true   || self =~ (/(true|t|yes|y|1)$/i)
    return false  if self == false  || self.blank? || self =~ (/(false|f|no|n|0)$/i)
    raise ArgumentError.new("invalid value for Boolean: \"#{self}\"")
  end
end

Original: http://jeffgardner.org/2011/08/04/rails-string-to-boolean-method/

I have just made the wannabe_bool gem to convert strings, integers, symbols and nil values to boolean, using a #to_b method.
https://github.com/prodis/wannabe_bool

'true'.to_b # => true
1.to_b      # => true
:true.to_b  # => true

'false'.to_b # => false
0.to_b       # => false
:false.to_b  # => false
nil.to_b     # => false

# and more

  module StringExtension
    extend ActiveSupport::Concern
    def to_bool
      result = false
      result = (!self.nil? && !(self.downcase.squish == 'false') && (self.downcase.squish == 'true' || self != '0' || self == '1'))

      result
    end
  end

so after defining my module, I just include it. And I don't want that to effect system wide.

 String.class_eval do
    include StringExtension
  end

Examples:

[13] pry(#<ProductFinder>)> >> "1".to_bool 
=> true
[14] pry(#<ProductFinder>)> 
[15] pry(#<ProductFinder>)> >> "0".to_bool 
=> false
[16] pry(#<ProductFinder>)> 
[17] pry(#<ProductFinder>)> >> "sdfj".to_bool 
=> true
[18] pry(#<ProductFinder>)> 
[19] pry(#<ProductFinder>)> >> "true".to_bool 
=> true
[20] pry(#<ProductFinder>)> 
[21] pry(#<ProductFinder>)> >> "false".to_bool
=> false

blank? throws a NoMethodError in Ruby 2.2.1, I think because blank? is now replaced with empty?

@pacharanero, #blank? is Ruby on Rails method only.

@rubyrider: can't to_bool be written more simply?

def to_bool
    (!self.nil? && !(self.downcase.squish == 'false') && (self.downcase.squish == 'true' || self != '0' || self == '1'))
end

Also, I still don't understand how the approach doesn't effect things 'system wide'

Aren't you still monkeypatching String?

You are using class_eval which is more flexible than

class Foo
#monkeypatch here
end

but it still looks like a system wide monkeypatch to me.

please correct me if I'm wrong, I'd like to know more.

http://stackoverflow.com/questions/9399358/monkey-patching-vs-class-eval

Am I missing something? What is extend ActiveSupport::Concern doing here?

My approach to avoid affect whole system:

# This module add refinements to cast string to boolean
module StringToBooleanRefinements
    refine String do
      def to_bool
        return true   if self == true   || self =~ (/(true|t|yes|y|1)$/i)
        return false  if self == false  || self.blank? || self =~ (/(false|f|no|n|0)$/i)
        raise ArgumentError.new("invalid value for Boolean: \"#{self}\"")
      end
  end
end

Class that will uses this refinement

class RefinedStringClass
  using StringToBooleanRefinements

   def string_true
       'true'.to_bool   
   end
   def string_false
      'false'.to_bool
   end
end

(For reference, Ruby refinements was introduced in Ruby 2.0. So if you are stuck on some antique version, it will not work.)