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

Returns:



# File 'object.c'

/*
 *  call-seq:
 *     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()
{
    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'

/*
 *  call-seq:
 *     obj == other        => true or false
 *     obj.equal?(other)   => true or false
 *     obj.eql?(other)     => true or false
 *  
 *  Equality---At the <code>Object</code> level, <code>==</code> returns
 *  <code>true</code> only if <i>obj</i> and <i>other</i> are the
 *  same object. Typically, this method is overridden in descendent
 *  classes to provide class-specific meaning.
 *
 *  Unlike <code>==</code>, the <code>equal?</code> method should never be
 *  overridden by subclasses: it is used to determine object identity
 *  (that is, <code>a.equal?(b)</code> iff <code>a</code> is the same
 *  object as <code>b</code>).
 *
 *  The <code>eql?</code> method returns <code>true</code> if
    <i>obj</i> and <i>anObject</i> have the
 *  same value. Used by <code>Hash</code> to test members for equality.
 *  For objects of class <code>Object</code>, <code>eql?</code> is
 *  synonymous with <code>==</code>. Subclasses normally continue this
 *  tradition, but there are exceptions. <code>Numeric</code> types, for
 *  example, perform type conversion across <code>==</code>, but not
 *  across <code>eql?</code>, so:
 *     
 *     1 == 1.0     #=> true
 *     1.eql? 1.0   #=> false
 */

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

#id2nameString #to_sString

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"

Overloads:



# File 'object.c'

/*
 *  call-seq:
 *     sym.id2name   => string
 *     sym.to_s      => string
 *  
 *  Returns the name or string corresponding to <i>sym</i>.
 *     
 *     :fred.id2name   #=> "fred"
 */


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

#inspectString

Returns the representation of sym as a symbol literal.

:fred.inspect   #=> ":fred"

Returns:



# File 'object.c'

/*
 *  call-seq:
 *     sym.inspect    => string
 *  
 *  Returns the representation of <i>sym</i> as a symbol literal.
 *     
 *     :fred.inspect   #=> ":fred"
 */

static VALUE
sym_inspect(sym)
    VALUE sym;
{
    VALUE str;
    const 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);
    }
    return str;
}

#to_iFixnum

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'

/*
 *  call-seq:
 *     sym.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
 */

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

    return LONG2FIX(id);
}

#to_intObject

:nodoc:



# File 'object.c'

/* :nodoc: */

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

#to_procObject

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

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


# File 'object.c'

/*
 * call-seq:
 *   sym.to_proc
 *
 * Returns a _Proc_ object which respond to the given method by _sym_.
 *
 *   (1..3).collect(&:to_s)  #=> ["1", "2", "3"]
 */

static VALUE
sym_to_proc(VALUE sym)
{
    return rb_proc_new(sym_call, (VALUE)SYM2ID(sym));
}

#id2nameString #to_sString

Returns the name or string corresponding to sym.

:fred.id2name   #=> "fred"

Overloads:



# File 'object.c'

/*
 *  call-seq:
 *     sym.id2name   => string
 *     sym.to_s      => string
 *  
 *  Returns the name or string corresponding to <i>sym</i>.
 *     
 *     :fred.id2name   #=> "fred"
 */


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

#to_symObject

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'

/*
 * call-seq:
 *   sym.to_sym   => sym
 *
 * In general, <code>to_sym</code> returns the <code>Symbol</code> corresponding
 * to an object. As <i>sym</i> is already a symbol, <code>self</code> is returned
 * in this case.
 */

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