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Class: NilClass

Relationships & Source Files
Inherits: Object
Defined in: object.c,
nilclass.rb,
object.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 1690



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 1645



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


  








  

    #==(other)  ⇒ Boolean   



  

    
Alias for Object#eql?. Returns whether self and other are the same object:


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


Here in class Object, #==, #equal?, and #eql? are the same method.
A subclass may override #== to provide class-specific meaning.


Unlike #==, the #equal? method should never be overridden by
subclasses as it is used to determine object identity (that is,
a.equal?(b) if and only if a is the same
object as b):


obj = "a"
other = obj.dup

obj == other      #=> true
obj.equal? other  #=> false
obj.equal? obj    #=> true


The #eql? method returns true if obj and other
refer to the same hash key.  This is used by ::Hash to test members
for equality.  For any pair of objects where #eql? returns true,
the #hash value of both objects must be equal. So any subclass
that overrides #eql? should also override #hash appropriately.


For objects of class ::Object, #eql?  is synonymous
with #==.  Subclasses normally continue this tradition by aliasing
#eql? to their overridden #== method, but there are exceptions.
::Numeric types, for example, perform type conversion across #==,
but not across #eql?, so:


1 == 1.0     #=> true
1.eql? 1.0   #=> false

  









  

    #===  
  

  [ GitHub ]






  

    #=~(object)  ⇒ nil   



  

    
Returns nil.


This method makes it useful to write:


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

  



  [ GitHub ]


  

  


# File 'object.c', line 1500



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


  








  

    #^  
  

  [ GitHub ]






  

    #inspect  ⇒ 'nil'   



  

    
Returns string 'nil':


nil.inspect # => "nil"

  



  [ GitHub ]


  

  


# File 'object.c', line 1480



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 'nilclass.rb', line 12



def rationalize(eps = nil)
  0r
end


  








  

    #to_a  ⇒ Array   



  

    
Returns an empty ::Array.


nil.to_a # => []

  



  [ GitHub ]


  

  


# File 'object.c', line 1446



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 'nilclass.rb', line 24



def to_c
  0i
end


  








  

    #to_f  ⇒ 0.0   



  

    
Always returns zero.


nil.to_f   #=> 0.0

  



  [ GitHub ]


  

  


# File 'nilclass.rb', line 48



def to_f
  return 0.0
end


  








  

    #to_h  ⇒ {}   



  

    
Returns an empty ::Hash.


nil.to_h   #=> {}

  



  [ GitHub ]


  

  


# File 'object.c', line 1464



static VALUE
nil_to_h(VALUE obj)
{
    return rb_hash_new_capa(0);
}


  








  

    #to_i  ⇒ 0   



  

    
Always returns zero.


nil.to_i   #=> 0

  



  [ GitHub ]


  

  


# File 'nilclass.rb', line 36



def to_i
  return 0
end


  








  

    #to_r  ⇒ 1   



  

    
Returns zero as a ::Rational:


nil.to_r # => (0/1)

  



  [ GitHub ]


  

  


# File 'nilclass.rb', line 60



def to_r
  0r
end


  








  

    #to_s  ⇒ ''   



  

    
Returns an empty ::String:


nil.to_s # => ""

  



  [ GitHub ]


  

  


# File 'object.c', line 1428



VALUE
rb_nil_to_s(VALUE obj)
{
    return rb_cNilClass_to_s;
}


  








  

    #|  
  

  [ GitHub ]