Class: Symbol

Inherits:
Object show all
Defined in:
object.c

Overview

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.id   #=> 2514190
$f2.id   #=> 2514190
$f3.id   #=> 2514190

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.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, :$=, :ThreadGroup,
                                :wait2, :$>]

Returns:




# File 'object.c'

VALUE
rb_sym_all_symbols()
{
    VALUE ary = rb_ary_new2(sym_tbl->num_entries);

    st_foreach(sym_tbl, symbols_i, ary);
    return ary;
}

Instance Method Details

#==(other) ⇒ Boolean #equal?(other) ⇒ Boolean #eql?(other) ⇒ Boolean

Equality---At the Object level, == returns true only if obj and other are the same object. Typically, this method is overridden in descendent classes to provide class-specific meaning.

Unlike ==, the equal? method should never be overridden by subclasses: it is used to determine object identity (that is, a.equal?(b) iff a is the same object as b).

The eql? method returns true if

<i>obj</i> and <i>anObject</i> have the

same value. Used by Hash to test members for equality. For objects of class Object, eql? is synonymous with ==. Subclasses normally continue this tradition, but there are exceptions. Numeric types, for example, perform type conversion across ==, but not across eql?, so:

1 == 1.0     #=> true
1.eql? 1.0   #=> false

Overloads:

  • #==(other) ⇒ Boolean

    Returns:

    • (Boolean)
  • #equal?(other) ⇒ Boolean

    Returns:

    • (Boolean)
  • #eql?(other) ⇒ Boolean

    Returns:

    • (Boolean) 



# File 'object.c'

static VALUE
rb_obj_equal(obj1, obj2)
    VALUE obj1, obj2;
{
    if (obj1 == obj2) return Qtrue;
    return Qfalse;
}

#id2name ⇒ String #to_s ⇒ String

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"

Overloads:




# File 'object.c'

static VALUE
sym_to_s(sym)
    VALUE sym;
{
    return rb_str_new2(rb_id2name(SYM2ID(sym)));
}

#inspect ⇒ String

Returns the representation of sym as a symbol literal.

:fred.inspect   #=> ":fred"

Returns:




# File 'object.c'

static VALUE
sym_inspect(sym)
VALUE sym;
{
VALUE str;
char *name;
ID id = SYM2ID(sym);

name = rb_id2name(id);
str = rb_str_new(0, strlen(name)+1);
RSTRING(str)->ptr[0] = ':';
strcpy(RSTRING(str)->ptr+1, name);
if (!rb_symname_p(name)) {
str = rb_str_dump(str);
strncpy(RSTRING(str)->ptr, ":\"", 2);
}

#to_i ⇒ Fixnum

Returns an integer that is unique for each symbol within a particular execution of a program.

:fred.to_i           #=> 9809
"fred".to_sym.to_i   #=> 9809

Returns:




# File 'object.c'

static VALUE
sym_to_i(sym)
    VALUE sym;
{
    ID id = SYM2ID(sym);

    return LONG2FIX(id);
}

#to_int ⇒ Object

:nodoc:




# File 'object.c'

static VALUE
sym_to_int(sym)
    VALUE sym;
{
    rb_warning("treating Symbol as an integer");
    return sym_to_i(sym);
}

#id2name ⇒ String #to_s ⇒ String

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"

Overloads:




# File 'object.c'

static VALUE
sym_to_s(sym)
    VALUE sym;
{
    return rb_str_new2(rb_id2name(SYM2ID(sym)));
}

#to_sym ⇒ Object

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




# File 'object.c'

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