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:

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

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.

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

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)

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

# File nilclass.rb, line 22
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 10
def to_i
  return 0
end

to_r → (0/1)

Returns zero as a Rational:

nil.to_r # => (0/1)

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

to_s → ''

Returns an empty String:

nil.to_s # => ""

VALUE
rb_nil_to_s(VALUE obj)
{
    return rb_cNilClass_to_s;
}

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