Symbol objects represent names and some strings 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
Methods
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Included Modules
Class Public methods
Symbol.all_symbols => array

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, :$=, :ThreadGroup,
                                :wait2, :$>]
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;
}
json_create(o)

Deserializes JSON string by converting the string value stored in the object to a Symbol

# File ext/json/lib/json/add/symbol.rb, line 22
def self.json_create(o)
  o['s'].to_sym
end
Instance Public methods
symbol <=> other_symbol → -1, 0, +1 or nil

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.

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));
}
sym == obj → true or false

Equality—If sym and obj are exactly the same symbol, returns true.

#define sym_equal rb_obj_equal
sym == obj → true or false

Equality—If sym and obj are exactly the same symbol, returns true.

#define sym_equal rb_obj_equal
sym =~ obj → fixnum or nil

Returns sym.to_s =~ obj.

static VALUE
sym_match(VALUE sym, VALUE other)
{
    return rb_str_match(rb_sym2str(sym), other);
}
sym[idx] → char
sym[b, n] → string

Returns sym.to_s[].

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

Returns a hash, that will be turned into a JSON object and represent this object.

# File ext/json/lib/json/add/symbol.rb, line 9
def as_json(*)
  {
    JSON.create_id => self.class.name,
    's'            => to_s,
  }
end
sym.capitalize → symbol

Same as sym.to_s.capitalize.intern.

static VALUE
sym_capitalize(VALUE sym)
{
    return rb_str_intern(rb_str_capitalize(rb_sym2str(sym)));
}
sym.casecmp(other) → -1, 0, +1 or nil

Case-insensitive version of Symbol#<=>.

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

provides a unified clone operation, for REXML::XPathParser to use across multiple Object types

# File lib/rexml/xpath_parser.rb, line 18
def dclone ; self ; end
sym.downcase → symbol

Same as sym.to_s.downcase.intern.

static VALUE
sym_downcase(VALUE sym)
{
    return rb_str_intern(rb_str_downcase(rb_sym2str(sym)));
}
sym.empty? → true or false

Returns that sym is :“” or not.

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

Returns the Encoding object that represents the encoding of sym.

static VALUE
sym_encoding(VALUE sym)
{
    return rb_obj_encoding(rb_sym2str(sym));
}
sym.id2name → string

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"
VALUE
rb_sym_to_s(VALUE sym)
{
    return str_new_shared(rb_cString, rb_sym2str(sym));
}
sym.inspect → string

Returns the representation of sym as a symbol literal.

:fred.inspect   #=> ":fred"
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;
}
sym.intern → sym

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

static VALUE
sym_to_sym(VALUE sym)
{
    return sym;
}
sym.length → integer

Same as sym.to_s.length.

static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_sym2str(sym));
}
sym.match(obj) → fixnum or nil

Returns sym.to_s =~ obj.

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

Same as sym.to_s.succ.intern.

static VALUE
sym_succ(VALUE sym)
{
    return rb_str_intern(rb_str_succ(rb_sym2str(sym)));
}
sym.size → integer

Same as sym.to_s.length.

static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_sym2str(sym));
}
sym.slice(idx) → char
sym.slice(b, n) → string

Returns sym.to_s[].

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

Same as sym.to_s.succ.intern.

static VALUE
sym_succ(VALUE sym)
{
    return rb_str_intern(rb_str_succ(rb_sym2str(sym)));
}
sym.swapcase → symbol

Same as sym.to_s.swapcase.intern.

static VALUE
sym_swapcase(VALUE sym)
{
    return rb_str_intern(rb_str_swapcase(rb_sym2str(sym)));
}
to_json(*a)

Stores class name (Symbol) with String representation of Symbol as a JSON string.

# File ext/json/lib/json/add/symbol.rb, line 17
def to_json(*a)
  as_json.to_json(*a)
end
sym.to_proc

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

(1..3).collect(&:to_s)  #=> ["1", "2", "3"]
VALUE
rb_sym_to_proc(VALUE sym)
{
}
sym.to_s → string

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"
VALUE
rb_sym_to_s(VALUE sym)
{
    return str_new_shared(rb_cString, rb_sym2str(sym));
}
sym.to_sym → sym

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

static VALUE
sym_to_sym(VALUE sym)
{
    return sym;
}
sym.upcase → symbol

Same as sym.to_s.upcase.intern.

static VALUE
sym_upcase(VALUE sym)
{
    return rb_str_intern(rb_str_upcase(rb_sym2str(sym)));
}