class Symbol

Symbol objects represent named identifiers inside the Ruby interpreter. They
are generated using the <code>:name</code> and
<code>:"string"</code> literals syntax, and by the various
<code>to_sym</code> 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 <code>Fred</code> is a constant in one context, a method in
another, and a class in a third, the Symbol <code>:Fred</code>
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

Constant, method, and variable names are returned as symbols:

module One
  Two = 2
  def three; 3 end
  @four = 4
  @@five = 5
  $six = 6
end
seven = 7

One.constants
# => [:Two]
One.instance_methods(true)
# => [:three]
One.instance_variables
# => [:@four]
One.class_variables
# => [:@@five]
global_variables.grep(/six/)
# => [:$six]
local_variables
# => [:seven]

Symbol objects are different from String objects in that Symbol objects represent identifiers, while String objects represent text or data.

Public Class Methods

all_symbols → array click to toggle source

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, :$=, :ThreadGroup,
                                :wait2, :$>]
static VALUE
sym_all_symbols(VALUE _)
{
    return rb_sym_all_symbols();
}
json_create(o) click to toggle source

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

Public Instance Methods

symbol <=> other_symbol → -1, 0, +1, or nil click to toggle source

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 click to toggle source

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

#define sym_equal rb_obj_equal
Also aliased as: ===

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

Alias for: ==
sym =~ obj → integer or nil click to toggle source

Returns sym.to_s =~ obj.

static VALUE
sym_match(VALUE sym, VALUE other)
{
    return rb_str_match(rb_sym2str(sym), other);
}
sym[idx] → char click to toggle source
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));
}
Also aliased as: slice
as_json(*) click to toggle source

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
capitalize → symbol click to toggle source
capitalize([options]) → symbol

Same as sym.to_s.capitalize.intern.

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, 0, +1, or nil click to toggle source

Case-insensitive version of Symbol#<=>. Currently, case-insensitivity only works on characters A-Z/a-z, not all of Unicode. This is different from Symbol#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
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, false, or nil click to toggle source

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
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));
}
downcase → symbol click to toggle source
downcase([options]) → symbol

Same as sym.to_s.downcase.intern.

static VALUE
sym_downcase(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_intern(rb_str_downcase(argc, argv, rb_sym2str(sym)));
}
empty? → true or false click to toggle source

Returns whether sym is :“” or not.

static VALUE
sym_empty(VALUE sym)
{
    return rb_str_empty(rb_sym2str(sym));
}
encoding → encoding click to toggle source

Returns the Encoding object that represents the encoding of sym.

static VALUE
sym_encoding(VALUE sym)
{
    return rb_obj_encoding(rb_sym2str(sym));
}
end_with?([suffixes]+) → true or false click to toggle source

Returns true if sym ends with one of the suffixes given.

:hello.end_with?("ello")               #=> true

# returns true if one of the +suffixes+ matches.
:hello.end_with?("heaven", "ello")     #=> true
:hello.end_with?("heaven", "paradise") #=> false
static VALUE
sym_end_with(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_end_with(argc, argv, rb_sym2str(sym));
}
id2name → string

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"
:ginger.to_s    #=> "ginger"

Note that this string is not frozen (unlike the symbol itself). To get a frozen string, use name.

Alias for: to_s
inspect → string click to toggle source

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;
}
intern → sym click to toggle source

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;
}
Also aliased as: to_sym
length → integer click to toggle source

Same as sym.to_s.length.

static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_sym2str(sym));
}
Also aliased as: size
match(pattern) → matchdata or nil click to toggle source
match(pattern, pos) → matchdata or nil

Returns sym.to_s.match.

static VALUE
sym_match_m(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_match_m(argc, argv, rb_sym2str(sym));
}
match?(pattern) → true or false click to toggle source
match?(pattern, pos) → true or false

Returns sym.to_s.match?.

static VALUE
sym_match_m_p(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_match_m_p(argc, argv, sym);
}
name → string click to toggle source

Returns the name or string corresponding to sym. Unlike to_s, the returned string is frozen.

:fred.name         #=> "fred"
:fred.name.frozen? #=> true
:fred.to_s         #=> "fred"
:fred.to_s.frozen? #=> false
VALUE
rb_sym2str(VALUE sym)
{

}

Same as sym.to_s.succ.intern.

Alias for: succ
size → integer

Same as sym.to_s.length.

Alias for: length
slice(idx) → char
slice(b, n) → string

Returns sym.to_s[].

Alias for: []
start_with?([prefixes]+) → true or false click to toggle source

Returns true if sym starts with one of the prefixes given. Each of the prefixes should be a String or a Regexp.

:hello.start_with?("hell")               #=> true
:hello.start_with?(/H/i)                 #=> true

# returns true if one of the prefixes matches.
:hello.start_with?("heaven", "hell")     #=> true
:hello.start_with?("heaven", "paradise") #=> false
static VALUE
sym_start_with(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_start_with(argc, argv, rb_sym2str(sym));
}
succ click to toggle source

Same as sym.to_s.succ.intern.

static VALUE
sym_succ(VALUE sym)
{
    return rb_str_intern(rb_str_succ(rb_sym2str(sym)));
}
Also aliased as: next
swapcase → symbol click to toggle source
swapcase([options]) → symbol

Same as sym.to_s.swapcase.intern.

static VALUE
sym_swapcase(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_intern(rb_str_swapcase(argc, argv, rb_sym2str(sym)));
}
to_json(*a) click to toggle source

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
to_proc click to toggle source

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

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

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"
:ginger.to_s    #=> "ginger"

Note that this string is not frozen (unlike the symbol itself). To get a frozen string, use name.

VALUE
rb_sym_to_s(VALUE sym)
{
    return str_new_shared(rb_cString, rb_sym2str(sym));
}
Also aliased as: id2name
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.

Alias for: intern
upcase → symbol click to toggle source
upcase([options]) → symbol

Same as sym.to_s.upcase.intern.

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