class NilClass

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:

Public Instance Methods

false & object → false
nil & object → false

Returns false:

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

Argument object is evaluated:

false & raise # Raises RuntimeError.

static VALUE
false_and(VALUE obj, VALUE obj2)
{
    return Qfalse;
}
true === other → true or false
false === other → true or false
nil === other → true or false

Returns true or false.

Like Object#==, if object is an instance of Object (and not an instance of one of its many subclasses).

This method is commonly overridden by those subclasses, to provide meaningful semantics in case statements.

#define case_equal rb_equal
nil =~ object → nil

Returns nil.

This method makes it useful to write:

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

static VALUE
nil_match(VALUE obj1, VALUE obj2)
{
    return Qnil;
}
false ^ object → true or false
nil ^ object → true or false

Returns false if object is nil or false, true otherwise:

nil ^ nil        # => false
nil ^ false      # => false
nil ^ Object.new # => true

#define false_xor true_and
false | object → true or false
nil | object → true or false

Returns false if object is nil or false, true otherwise:

nil | nil        # => false
nil | false      # => false
nil | Object.new # => true

#define false_or true_and
inspect → 'nil'

Returns string 'nil':

nil.inspect # => "nil"

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

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

static VALUE
rb_true(VALUE obj)
{
    return Qtrue;
}
rationalize(eps = nil) → (0/1)

Returns zero as a Rational:

nil.rationalize # => (0/1)

Argument eps is ignored.

# File nilclass.rb, line 12
def rationalize(eps = nil)
  0r
end
to_a → []

Returns an empty Array.

nil.to_a # => []

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)

# File nilclass.rb, line 24
def to_c
  0i
end
to_f → 0.0

Always returns zero.

nil.to_f   #=> 0.0

# File nilclass.rb, line 48
def to_f
  return 0.0
end
to_h → {}

Returns an empty Hash.

nil.to_h   #=> {}

static VALUE
nil_to_h(VALUE obj)
{
    return rb_hash_new();
}
to_i → 0

Always returns zero.

nil.to_i   #=> 0

# File nilclass.rb, line 36
def to_i
  return 0
end
to_r → (0/1)

Returns zero as a Rational:

nil.to_r # => (0/1)

# File nilclass.rb, line 60
def to_r
  0r
end
to_s → ''

Returns an empty String:

nil.to_s # => ""

VALUE
rb_nil_to_s(VALUE obj)
{
    return rb_cNilClass_to_s;
}