* array.c (rb_ary_s_try_convert): a new class method to convert

  object or nil if it's not target-type.  this mechanism is used
  to convert types in the C implemented methods.

* hash.c (rb_hash_s_try_convert): ditto.

* io.c (rb_io_s_try_convert): ditto.

* re.c (rb_reg_s_try_convert): ditto.

* string.c (rb_str_s_try_convert): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13251 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 18 insertions, 0 deletions

diff --git a/io.c b/io.c
index 069ba21df0..850c1a657e 100644
--- a/io.c
+++ b/io.c
@@ -242,6 +242,23 @@ rb_io_check_io(VALUE io)
     return rb_check_convert_type(io, T_FILE, "IO", "to_io");
 }
 
+/*
+ *  call-seq:
+ *     IO.try_convert(obj) -> io or nil
+ *
+ *  Try to convert <i>obj</i> into an IO, using to_io method.
+ *  Returns converted IO or nil if <i>obj</i> cannot be converted
+ *  for any reason.
+ *
+ *     IO.try_convert(STDOUT)     # => STDOUT
+ *     IO.try_convert("STDOUT")   # => nil
+ */
+static VALUE
+rb_io_s_try_convert(VALUE dummy, VALUE io)
+{
+    return rb_io_check_io(io);
+}
+
 static void
 io_unread(rb_io_t *fptr)
 {
@@ -5708,6 +5725,7 @@ Init_IO(void)
     rb_define_singleton_method(rb_cIO, "read", rb_io_s_read, -1);
     rb_define_singleton_method(rb_cIO, "select", rb_f_select, -1);
     rb_define_singleton_method(rb_cIO, "pipe", rb_io_s_pipe, 0);
+    rb_define_singleton_method(rb_cIO, "try_convert", rb_io_s_try_convert, 1);
 
     rb_define_method(rb_cIO, "initialize", rb_io_initialize, -1);