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Class: Symbol

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, ::Comparable
Inherits: Object
Defined in: string.c,
string.c,
symbol.c

Overview

Symbol objects represent names inside the Ruby interpreter. They are generated using the :name and :"string" literals syntax, and by the various #to_sym methods. The same Symbol object will be created for a given name or string for the duration of a program's execution, regardless of the context or meaning of that name. Thus if Fred is a constant in one context, a method in another, and a class in a third, the Symbol :Fred will be the same object in all three contexts.

module One
  class Fred
  end
  $f1 = :Fred
end
module Two
  Fred = 1
  $f2 = :Fred
end
def Fred()
end
$f3 = :Fred
$f1.object_id   #=> 2514190
$f2.object_id   #=> 2514190
$f3.object_id   #=> 2514190

Class Method Summary

Instance Attribute Summary

Instance Method Summary

::Comparable - Included

#<

Compares two objects based on the receiver's #<=> method, returning true if it returns a value less than 0.

#<=

Compares two objects based on the receiver's #<=> method, returning true if it returns a value less than or equal to 0.

#==

Compares two objects based on the receiver's #<=> method, returning true if it returns 0.

#>

Compares two objects based on the receiver's #<=> method, returning true if it returns a value greater than 0.

#>=

Compares two objects based on the receiver's #<=> method, returning true if it returns a value greater than or equal to 0.

#between?

Returns false if obj #<=> min is less than zero or if anObject #<=> max is greater than zero, true otherwise.

#clamp

Returns min if obj #<=> min is less than zero, max if obj #<=> max is greater than zero and obj otherwise.

Class Method Details

.all_symbolsArray

Returns an array of all the symbols currently in Ruby's symbol table.

Symbol.all_symbols.size    #=> 903
Symbol.all_symbols[1,20]   #=> [:floor, :ARGV, :Binding, :symlink,
                                :chown, :EOFError, :$;, :String,
                                :LOCK_SH, :"setuid?", :$<,
                                :default_proc, :compact, :extend,
                                :Tms, :getwd, :$=, :ThreadGroup,
                                :wait2, :$>]
[ GitHub ]

  
# File 'symbol.c', line 862

VALUE
rb_sym_all_symbols(void)
{
    VALUE ary = rb_ary_new2(global_symbols.str_sym->num_entries);
    st_foreach(global_symbols.str_sym, symbols_i, ary);
    return ary;
}

Instance Attribute Details

#empty?Boolean (readonly)

Returns whether sym is :“” or not.

[ GitHub ]

  
# File 'string.c', line 10972

static VALUE
sym_empty(VALUE sym)
{
    return rb_str_empty(rb_sym2str(sym));
}

Instance Method Details

#<=>(other_symbol) ⇒ 1, ...

Compares symbol with other_symbol after calling #to_s on each of the symbols. Returns -1, 0, +1, or nil depending on whether symbol is less than, equal to, or greater than other_symbol.

nil is returned if the two values are incomparable.

See String#<=> for more information.

[ GitHub ]

  
# File 'string.c', line 10827

static VALUE
sym_cmp(VALUE sym, VALUE other)
{
    if (!SYMBOL_P(other)) {
	return Qnil;
    }
    return rb_str_cmp_m(rb_sym2str(sym), rb_sym2str(other));
}

#==

[ GitHub ]

#===

[ GitHub ]

#=~(obj) ⇒ Integer?

Returns sym.to_s =~ obj.

[ GitHub ]

  
# File 'string.c', line 10901

static VALUE
sym_match(VALUE sym, VALUE other)
{
    return rb_str_match(rb_sym2str(sym), other);
}

#[](idx) ⇒ String #[](b, n) ⇒ String #slice(idx) ⇒ String #slice(b, n) ⇒ String
Also known as: #slice

Returns sym.to_s[].

[ GitHub ]

  
# File 'string.c', line 10945

static VALUE
sym_aref(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_aref_m(argc, argv, rb_sym2str(sym));
}

#capitalizeSymbol #capitalize([options]) ⇒ Symbol

Same as sym.to_s.capitalize.intern.

[ GitHub ]

  
# File 'string.c', line 11014

static VALUE
sym_capitalize(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_intern(rb_str_capitalize(argc, argv, rb_sym2str(sym)));
}

#casecmp(other_symbol) ⇒ 1, ...

Case-insensitive version of #<=>. Currently, case-insensitivity only works on characters A-Z/a-z, not all of Unicode. This is different from #casecmp?.

:aBcDeF.casecmp(:abcde)     #=> 1
:aBcDeF.casecmp(:abcdef)    #=> 0
:aBcDeF.casecmp(:abcdefg)   #=> -1
:abcdef.casecmp(:ABCDEF)    #=> 0

nil is returned if the two symbols have incompatible encodings, or if other_symbol is not a symbol.

:foo.casecmp(2)   #=> nil
"\u{e4 f6 fc}".encode("ISO-8859-1").to_sym.casecmp(:"\u{c4 d6 dc}")   #=> nil
[ GitHub ]

  
# File 'string.c', line 10856

static VALUE
sym_casecmp(VALUE sym, VALUE other)
{
    if (!SYMBOL_P(other)) {
	return Qnil;
    }
    return str_casecmp(rb_sym2str(sym), rb_sym2str(other));
}

#casecmp?(other_symbol) ⇒ true, ...

Returns true if sym and other_symbol are equal after Unicode case folding, false if they are not equal.

:aBcDeF.casecmp?(:abcde)     #=> false
:aBcDeF.casecmp?(:abcdef)    #=> true
:aBcDeF.casecmp?(:abcdefg)   #=> false
:abcdef.casecmp?(:ABCDEF)    #=> true
:"\u{e4 f6 fc}".casecmp?(:"\u{c4 d6 dc}")   #=> true

nil is returned if the two symbols have incompatible encodings, or if other_symbol is not a symbol.

:foo.casecmp?(2)   #=> nil
"\u{e4 f6 fc}".encode("ISO-8859-1").to_sym.casecmp?(:"\u{c4 d6 dc}")   #=> nil
[ GitHub ]

  
# File 'string.c', line 10885

static VALUE
sym_casecmp_p(VALUE sym, VALUE other)
{
    if (!SYMBOL_P(other)) {
	return Qnil;
    }
    return str_casecmp_p(rb_sym2str(sym), rb_sym2str(other));
}

#downcaseSymbol #downcase([options]) ⇒ Symbol

Same as sym.to_s.downcase.intern.

[ GitHub ]

  
# File 'string.c', line 11000

static VALUE
sym_downcase(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_intern(rb_str_downcase(argc, argv, rb_sym2str(sym)));
}

#encodingEncoding

Returns the ::Encoding object that represents the encoding of sym.

[ GitHub ]

  
# File 'string.c', line 11041

static VALUE
sym_encoding(VALUE sym)
{
    return rb_obj_encoding(rb_sym2str(sym));
}

#id2nameString #to_sString

Alias for #to_s.

#inspectString

Returns the representation of sym as a symbol literal.

:fred.inspect   #=> ":fred"
[ GitHub ]

  
# File 'string.c', line 10709

static VALUE
sym_inspect(VALUE sym)
{
    VALUE str = rb_sym2str(sym);
    const char *ptr;
    long len;
    char *dest;

    if (!rb_str_symname_p(str)) {
	str = rb_str_inspect(str);
	len = RSTRING_LEN(str);
	rb_str_resize(str, len + 1);
	dest = RSTRING_PTR(str);
	memmove(dest + 1, dest, len);
    }
    else {
	rb_encoding *enc = STR_ENC_GET(str);
	RSTRING_GETMEM(str, ptr, len);
	str = rb_enc_str_new(0, len + 1, enc);
	dest = RSTRING_PTR(str);
	memcpy(dest + 1, ptr, len);
    }
    dest[0] = ':';
    return str;
}

#to_symsym #internsym
Also known as: #to_sym

In general, #to_sym returns the Symbol corresponding to an object. As sym is already a symbol, self is returned in this case.

[ GitHub ]

  
# File 'string.c', line 10765

static VALUE
sym_to_sym(VALUE sym)
{
    return sym;
}

#lengthInteger #sizeInteger
Also known as: #size

Same as sym.to_s.length.

[ GitHub ]

  
# File 'string.c', line 10959

static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_sym2str(sym));
}

#match(pattern) ⇒ MatchData? #match(pattern, pos) ⇒ MatchData?

Returns sym.to_s.match.

[ GitHub ]

  
# File 'string.c', line 10915

static VALUE
sym_match_m(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_match_m(argc, argv, rb_sym2str(sym));
}

#match?(pattern) ⇒ Boolean #match?(pattern, pos) ⇒ Boolean

Returns sym.to_s.match?.

[ GitHub ]

  
# File 'string.c', line 10929

static VALUE
sym_match_m_p(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_match_m_p(argc, argv, sym);
}

#next Also known as: #succ

Same as sym.to_s.succ.intern.

[ GitHub ]

  
# File 'string.c', line 10807

static VALUE
sym_succ(VALUE sym)
{
    return rb_str_intern(rb_str_succ(rb_sym2str(sym)));
}

#lengthInteger #sizeInteger

Alias for #length.

#[](idx) ⇒ String #[](b, n) ⇒ String #slice(idx) ⇒ String #slice(b, n) ⇒ String

Alias for #[].

#next #succ

Alias for #next.

#swapcaseSymbol #swapcase([options]) ⇒ Symbol

Same as sym.to_s.swapcase.intern.

[ GitHub ]

  
# File 'string.c', line 11028

static VALUE
sym_swapcase(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_intern(rb_str_swapcase(argc, argv, rb_sym2str(sym)));
}

#to_procProc

Returns a Proc object which responds to the given method by sym.

(1..3).collect(&:to_s)  #=> ["1", "2", "3"]
[ GitHub ]

  
# File 'string.c', line 10793

VALUE
rb_sym_to_proc(VALUE sym)
{
}

#id2nameString #to_sString
Also known as: #id2name

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"
:ginger.to_s    #=> "ginger"
[ GitHub ]

  
# File 'string.c', line 10748

VALUE
rb_sym_to_s(VALUE sym)
{
    return str_new_shared(rb_cString, rb_sym2str(sym));
}

#to_symsym #internsym

Alias for #intern.

#upcaseSymbol #upcase([options]) ⇒ Symbol

Same as sym.to_s.upcase.intern.

[ GitHub ]

  
# File 'string.c', line 10986

static VALUE
sym_upcase(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_intern(rb_str_upcase(argc, argv, rb_sym2str(sym)));
}