* 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/string.c b/string.c
index efb380feb5..dd2d7473a8 100644
--- a/string.c
+++ b/string.c
@@ -615,6 +615,23 @@ rb_check_string_type(VALUE str)
     return str;
 }
 
+/*
+ *  call-seq:
+ *     String.try_convert(obj) -> string or nil
+ *
+ *  Try to convert <i>obj</i> into a String, using to_str method.
+ *  Returns converted regexp or nil if <i>obj</i> cannot be converted
+ *  for any reason.
+ *
+ *     String.try_convert("str")     # => str
+ *     String.try_convert(/re/)      # => nil
+ */
+static VALUE
+rb_str_s_try_convert(VALUE dummy, VALUE str)
+{
+    return rb_check_string_type(str);
+}
+
 VALUE
 rb_str_substr(VALUE str, long beg, long len)
 {
@@ -4877,6 +4894,7 @@ Init_String(void)
     rb_cString  = rb_define_class("String", rb_cObject);
     rb_include_module(rb_cString, rb_mComparable);
     rb_define_alloc_func(rb_cString, str_alloc);
+    rb_define_singleton_method(rb_cString, "try_convert", rb_str_s_try_convert, 1);
     rb_define_method(rb_cString, "initialize", rb_str_init, -1);
     rb_define_method(rb_cString, "initialize_copy", rb_str_replace, 1);
     rb_define_method(rb_cString, "<=>", rb_str_cmp_m, 1);