add {Array|Hash|String}.try_convert

2 files changed, 26 insertions, 0 deletions

diff --git a/mrbgems/mruby-string-ext/mrblib/string.rb b/mrbgems/mruby-string-ext/mrblib/string.rb
index 4c8a2ce3b..c699e13b7 100644
--- a/mrbgems/mruby-string-ext/mrblib/string.rb
+++ b/mrbgems/mruby-string-ext/mrblib/string.rb
@@ -1,6 +1,25 @@
 class String
 
   ##
+  #  call-seq:
+  #     String.try_convert(obj) -> string or nil
+  #
+  # Try to convert <i>obj</i> into a String, using to_str method.
+  # Returns converted string or nil if <i>obj</i> cannot be converted
+  # for any reason.
+  #
+  #     String.try_convert("str")     #=> "str"
+  #     String.try_convert(/re/)      #=> nil
+  #
+  def self.try_convert(obj)
+    if obj.respond_to?(:to_str)
+      obj.to_str
+    else
+      nil
+    end
+  end
+
+  ##
   # call-seq:
   #    string.clear    ->  string
   #
diff --git a/mrbgems/mruby-string-ext/test/string.rb b/mrbgems/mruby-string-ext/test/string.rb
index 8324a1613..37a5d28cf 100644
--- a/mrbgems/mruby-string-ext/test/string.rb
+++ b/mrbgems/mruby-string-ext/test/string.rb
@@ -3,6 +3,13 @@
 
 UTF8STRING = ("\343\201\202".size == 1)
 
+assert('String.try_convert') do
+  assert_nil String.try_convert(nil)
+  assert_nil String.try_convert(:foo)
+  assert_equal "", String.try_convert("")
+  assert_equal "1,2,3", String.try_convert("1,2,3")
+end
+
 assert('String#getbyte') do
   str1 = "hello"
   bytes1 = [104, 101, 108, 108, 111]