Comparison of existential checks in Rails

existential_rails.irb

# Does it have substance? Use .blank? or .present?, it's opposite:
>> "   ".blank?
=> true
>> nil.blank?
=> true
>> [].blank?
=> true
>> nil.present?
=> false
>> [].present?
=> false
>> "   ".present?
=> false

# Anything at all in there? Use .any? as the opposite of .empty?. Watch out for nils:
>> "   ".empty?
=> false
>> [].empty?
=> true
>> nil.empty?
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.empty?
>> "   ".any?
=> true
>> [].any?
=> false
>> nil.any?
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.any?
	from (irb):38

# Is it numerically zero? Even the .zero? method has an opposite: .nonzero?.
>> 0.zero?
=> true
>> [].zero?
NoMethodError: undefined method `zero?' for []:Array
>> "  ".zero?
NoMethodError: undefined method `zero?' for "  ":String
>> 0.nonzero?
=> nil
>> [].nonzero?
NoMethodError: undefined method `nonzero?' for []:Array
>> "  ".nonzero?
NoMethodError: undefined method `nonzero?' for "  ":String

# Is it actually nil? The opposite in this case is Ruby's boolean sense of an object itself:
>> nil.nil?
=> true
>> "  ".nil?
=> false
>> [].nil?
=> false
>> true if nil
=> nil
>> true if "  "
=> true
>> true if []
=> true