Class: NilClass

Inherits:
Object show all
Defined in:
object.c,
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:

  • #rationalize

  • #to_a

  • #to_c

  • #to_h

  • #to_r

  • #to_s

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 Method Summary collapse

Instance Method Details

#&(object) ⇒ false #&(object) ⇒ false

Returns false:

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

Argument object is evaluated:

false & raise # Raises RuntimeError.

Overloads:

  • #&(object) ⇒ false

    Returns:

    • (false)
  • #&(object) ⇒ false

    Returns:

    • (false) 


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# File 'object.c', line 1601

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

#=== ⇒ Object

#=~(object) ⇒ nil

Returns nil.

This method makes it useful to write:

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

Returns:

  • (nil) 


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# File 'object.c', line 1456

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

#^ ⇒ Object

#inspect ⇒ Object

Returns string 'nil':

nil.inspect # => "nil"



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# File 'object.c', line 1436

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

#nil? ⇒ true

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

Returns:

  • (true) 


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# File 'object.c', line 1646

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

#rationalize(eps = nil) ⇒ Object

Returns zero as a Rational:

nil.rationalize # => (0/1)

Argument eps is ignored.



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# 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 ⇒ Object

call-seq:

to_a -> []

Returns an empty Array.

nil.to_a # => []



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# File 'object.c', line 1402

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

#to_c ⇒ Object

Returns zero as a Complex:

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



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# File 'complex.c', line 1936

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

#to_h ⇒ Object

call-seq:

to_h -> {}

Returns an empty Hash.

nil.to_h   #=> {}



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# File 'object.c', line 1420

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

#to_r ⇒ Object

Returns zero as a Rational:

nil.to_r # => (0/1)



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# File 'rational.c', line 2119

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

#to_s ⇒ Object

Returns an empty String:

nil.to_s # => ""



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# File 'object.c', line 1384

VALUE
rb_nil_to_s(VALUE obj)
{
    return rb_cNilClass_to_s;
}

#| ⇒ Object