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Class: NilClass

Relationships & Source Files
Inherits: Object
Defined in: object.c,
complex.c,
nilclass.rb,
object.c,
rational.c

Overview

The class of the singleton object nil.

Several of its methods act as operators:

Others act as converters, carrying the concept of nullity to other classes:

While nil doesn’t have an explicitly defined #to_hash method, it can be used in ** unpacking, not adding any keyword arguments.

Another method provides inspection:

Finally, there is this query method:

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#nil? ⇒ Boolean (readonly)

Returns true. For all other objects, method nil? returns false.

[ GitHub ] 

  


# File 'object.c', line 1646



static VALUE
rb_true(VALUE obj)
{
    return Qtrue;
}


  







Instance Method Details



  

    

      #&(object)  ⇒ false 
      #&(object)  ⇒ false 
    

  



  

    

Returns false:



false & true       # => false
false & Object.new # => false



Argument object is evaluated:



false & raise # Raises RuntimeError.


  





  


  [ GitHub ]


  

  


# File 'object.c', line 1601



static VALUE
false_and(VALUE obj, VALUE obj2)
{
    return Qfalse;
}


  








  

    #===  
  

  [ GitHub ]






  

    #=~(object)  ⇒ nil   



  

    

Returns nil.



This method makes it useful to write:



while gets =~ /re/
  # ...
end


  



  [ GitHub ]


  

  


# File 'object.c', line 1456



static VALUE
nil_match(VALUE obj1, VALUE obj2)
{
    return Qnil;
}


  








  

    #^  
  

  [ GitHub ]






  

    #inspect  ⇒ 'nil'   



  

    

Returns string 'nil':



nil.inspect # => "nil"


  



  [ GitHub ]


  

  


# File 'object.c', line 1436



static VALUE
nil_inspect(VALUE obj)
{
    return rb_usascii_str_new2("nil");
}


  








  

    #rationalize(eps = nil)  ⇒ 1   



  

    

Returns zero as a ::Rational:



nil.rationalize # => (0/1)



Argument eps is ignored.


  



  [ GitHub ]


  

  


# File 'rational.c', line 2136



static VALUE
nilclass_rationalize(int argc, VALUE *argv, VALUE self)
{
    rb_check_arity(argc, 0, 1);
    return nilclass_to_r(self);
}


  








  

    #to_a  ⇒ Array   



  

    

Returns an empty ::Array.



nil.to_a # => []


  



  [ GitHub ]


  

  


# File 'object.c', line 1402



static VALUE
nil_to_a(VALUE obj)
{
    return rb_ary_new2(0);
}


  








  

    #to_c  ⇒ (0+0i)   



  

    

Returns zero as a ::Complex:



nil.to_c # => (0+0i)


  



  [ GitHub ]


  

  


# File 'complex.c', line 1936



static VALUE
nilclass_to_c(VALUE self)
{
    return rb_complex_new1(INT2FIX(0));
}


  








  

    #to_f  ⇒ 0.0   



  

    

Always returns zero.



nil.to_f   #=> 0.0


  



  [ GitHub ]


  

  


# File 'nilclass.rb', line 22



def to_f
  return 0.0
end


  








  

    #to_h  ⇒ {}   



  

    

Returns an empty ::Hash.



nil.to_h   #=> {}


  



  [ GitHub ]


  

  


# File 'object.c', line 1420



static VALUE
nil_to_h(VALUE obj)
{
    return rb_hash_new();
}


  








  

    #to_i  ⇒ 0   



  

    

Always returns zero.



nil.to_i   #=> 0


  



  [ GitHub ]


  

  


# File 'nilclass.rb', line 10



def to_i
  return 0
end


  








  

    #to_r  ⇒ 1   



  

    

Returns zero as a ::Rational:



nil.to_r # => (0/1)


  



  [ GitHub ]


  

  


# File 'rational.c', line 2119



static VALUE
nilclass_to_r(VALUE self)
{
    return rb_rational_new1(INT2FIX(0));
}


  








  

    #to_s  ⇒ ''   



  

    

Returns an empty ::String:



nil.to_s # => ""


  



  [ GitHub ]


  

  


# File 'object.c', line 1384



VALUE
rb_nil_to_s(VALUE obj)
{
    return rb_cNilClass_to_s;
}


  








  

    #|  
  

  [ GitHub ]