NilClass

Class

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:

inspect

Finally, there is this query method:

nil?

Instance Methods

false & object → false

nil & object → false

object.c View on GitHub

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

Returns false:

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

Argument object is evaluated:

false & raise # Raises RuntimeError.

true === other → true or false

false === other → true or false

nil === other → true or false

object.c View on GitHub

          
            #define case_equal rb_equal

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.

nil =~ object → nil

object.c View on GitHub

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

Returns nil.

This method makes it useful to write:

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

false ^ object → true or false

nil ^ object → true or false

object.c View on GitHub

          
            #define false_xor true_and

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

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

inspect → 'nil'

object.c View on GitHub

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

Returns string 'nil':

nil.inspect # => "nil"

nil.nil? → true

object.c View on GitHub

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

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

rationalize(eps = nil) → (0/1)

rational.c View on GitHub

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

Returns zero as a Rational:

nil.rationalize # => (0/1)

Argument eps is ignored.

to_a → []

object.c View on GitHub

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

Returns an empty Array.

nil.to_a # => []

to_c → (0+0i)

complex.c View on GitHub

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

Returns zero as a Complex:

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

nil.to_f → 0.0

nilclass.rb View on GitHub

          
            # File tmp/rubies/ruby-3.4.1/nilclass.rb, line 22
def to_f
  return 0.0
end

Always returns zero.

nil.to_f   #=> 0.0

to_h → {}

object.c View on GitHub

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

Returns an empty Hash.

nil.to_h   #=> {}

nil.to_i → 0

nilclass.rb View on GitHub

          
            # File tmp/rubies/ruby-3.4.1/nilclass.rb, line 10
def to_i
  return 0
end

Always returns zero.

nil.to_i   #=> 0

to_r → (0/1)

rational.c View on GitHub

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

Returns zero as a Rational:

nil.to_r # => (0/1)

to_s → ''

object.c View on GitHub

          
            VALUE
rb_nil_to_s(VALUE obj)
{
    return rb_cNilClass_to_s;
}

Returns an empty String:

nil.to_s # => ""

false | object → true or false

nil | object → true or false

object.c View on GitHub

          
            #define false_or true_and

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

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