Class: Symbol

Inherits:
Object show all
Includes:
Comparable
Defined in:
string.c,
string.c

Overview

********************************************************************

Symbol objects represent names 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

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Comparable

#<, #<=, #>, #>=, #between?, #clamp

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:


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# File 'string.c', line 11196

static VALUE
sym_all_symbols(VALUE _)
{
    return rb_sym_all_symbols();
}

Instance Method Details

#<=>(other_symbol) ⇒ -1, ...

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.

Returns:

  • (-1, 0, +1, nil) 

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# File 'string.c', line 10886

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));
}

#== ⇒ Object

#=== ⇒ Object

#=~(obj) ⇒ Integer?

Returns sym.to_s =~ obj.

Returns:


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# File 'string.c', line 10960

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

#[](idx) ⇒ String #[](b, n) ⇒ String #slice(idx) ⇒ String #slice(b, n) ⇒ String

Returns sym.to_s[].

Overloads:


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# File 'string.c', line 11004

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

#capitalize ⇒ Object #capitalize([options]) ⇒ Object

Same as sym.to_s.capitalize.intern.


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# File 'string.c', line 11073

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, ...

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

Returns:

  • (-1, 0, +1, nil) 

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# File 'string.c', line 10915

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, ...

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

Returns:

  • (true, false, nil) 

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# File 'string.c', line 10944

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 ⇒ Object #downcase([options]) ⇒ Object

Same as sym.to_s.downcase.intern.


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# File 'string.c', line 11059

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

#empty? ⇒ Boolean

Returns whether sym is :“” or not.

Returns:

  • (Boolean) 

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# File 'string.c', line 11031

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

#encoding ⇒ Encoding

Returns the Encoding object that represents the encoding of sym.

Returns:


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# File 'string.c', line 11140

static VALUE
sym_encoding(VALUE sym)
{
    return rb_obj_encoding(rb_sym2str(sym));
}

#end_with?([suffixes]) ⇒ Boolean

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

Returns:

  • (Boolean) 

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# File 'string.c', line 11127

static VALUE
sym_end_with(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_end_with(argc, argv, rb_sym2str(sym));
}

#id2name ⇒ String #to_s ⇒ String

Returns the name or string corresponding to sym.

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

Overloads:


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# File 'string.c', line 10807

VALUE
rb_sym_to_s(VALUE sym)
{
    return str_new_shared(rb_cString, rb_sym2str(sym));
}

#inspect ⇒ String

Returns the representation of sym as a symbol literal.

:fred.inspect   #=> ":fred"

Returns:


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# File 'string.c', line 10768

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;
}

#to_sym ⇒ Object #intern ⇒ Object

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


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# File 'string.c', line 10824

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

#length ⇒ Integer #size ⇒ Integer

Same as sym.to_s.length.

Overloads:


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# File 'string.c', line 11018

static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_sym2str(sym));
}

#match(pattern) ⇒ MatchData? #match(pattern, pos) ⇒ MatchData?

Returns sym.to_s.match.

Overloads:


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# File 'string.c', line 10974

static VALUE
sym_match_m(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_match_m(argc, argv, rb_sym2str(sym));
}

#match?(pattern) ⇒ Boolean #match?(pattern, pos) ⇒ Boolean

Returns sym.to_s.match?.

Overloads:

  • #match?(pattern) ⇒ Boolean

    Returns:

    • (Boolean)
  • #match?(pattern, pos) ⇒ Boolean

    Returns:

    • (Boolean) 

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# File 'string.c', line 10988

static VALUE
sym_match_m_p(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_match_m_p(argc, argv, sym);
}

#succ ⇒ Object

Same as sym.to_s.succ.intern.


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# File 'string.c', line 10866

static VALUE
sym_succ(VALUE sym)
{
    return rb_str_intern(rb_str_succ(rb_sym2str(sym)));
}

#length ⇒ Integer #size ⇒ Integer

Same as sym.to_s.length.

Overloads:


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# File 'string.c', line 11018

static VALUE
sym_length(VALUE sym)
{
    return rb_str_length(rb_sym2str(sym));
}

#[](idx) ⇒ String #[](b, n) ⇒ String #slice(idx) ⇒ String #slice(b, n) ⇒ String

Returns sym.to_s[].

Overloads:


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# File 'string.c', line 11004

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

#start_with?([prefixes]) ⇒ Boolean

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

Returns:

  • (Boolean) 

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# File 'string.c', line 11108

static VALUE
sym_start_with(int argc, VALUE *argv, VALUE sym)
{
    return rb_str_start_with(argc, argv, rb_sym2str(sym));
}

#succ ⇒ Object

Same as sym.to_s.succ.intern.


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# File 'string.c', line 10866

static VALUE
sym_succ(VALUE sym)
{
    return rb_str_intern(rb_str_succ(rb_sym2str(sym)));
}

#swapcase ⇒ Object #swapcase([options]) ⇒ Object

Same as sym.to_s.swapcase.intern.


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# File 'string.c', line 11087

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

#to_proc ⇒ Object

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

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


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# File 'string.c', line 10852

VALUE
rb_sym_to_proc(VALUE sym)
{
}

#id2name ⇒ String #to_s ⇒ String

Returns the name or string corresponding to sym.

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

Overloads:


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# File 'string.c', line 10807

VALUE
rb_sym_to_s(VALUE sym)
{
    return str_new_shared(rb_cString, rb_sym2str(sym));
}

#to_sym ⇒ Object #intern ⇒ Object

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


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# File 'string.c', line 10824

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

#upcase ⇒ Object #upcase([options]) ⇒ Object

Same as sym.to_s.upcase.intern.


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# File 'string.c', line 11045

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