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Symbol

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

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, :$=, :ThreadGroup,
                                :wait2, :$>]
 
               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;
}
            

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

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) → -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 casecmp?.

 
               static VALUE
sym_casecmp(VALUE sym, VALUE other)
{
    if (!SYMBOL_P(other)) {
        return Qnil;
    }
    return rb_str_casecmp(rb_sym2str(sym), rb_sym2str(other));
}
            
casecmp?(other) → true, false, or nil click to toggle source

Returns true if sym and other are equal after Unicode case folding, false if they are not equal, and nil if other is not a symbol.

 
               static VALUE
sym_casecmp_p(VALUE sym, VALUE other)
{
    if (!SYMBOL_P(other)) {
        return Qnil;
    }
    return rb_str_casecmp_p(rb_sym2str(sym), rb_sym2str(other));
}
            
downcase [options] → symbol click to toggle source

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 that 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));
}
            
id2name → string click to toggle source

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));
}
            
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;
}
            
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));
}
            
match(obj) → MatchData or nil click to toggle source

Returns sym.to_s.match(obj).

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

Returns sym.to_s.match?(obj).

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

Same as sym.to_s.length.

 
               static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_sym2str(sym));
}
            
slice(idx) → char click to toggle source
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));
}
            
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)));
}
            
swapcase [options] → symbol click to toggle source

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_proc click to toggle source

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)
{
}
            
to_s → string click to toggle source

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));
}
            
to_sym → 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;
}
            
upcase [options] → symbol click to toggle source

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)));
}