Merge pull request #3034 from takahashim/try_convert

add {Array|Hash|String}.try_convert

mrbgems/mruby-array-ext/mrblib/array.rb

 class Array
+  ##
+  # call-seq:
+  #    Array.try_convert(obj) -> array or nil
+  #
+  # Tries to convert +obj+ into an array, using +to_ary+ method.
+  # converted array or +nil+ if +obj+ cannot be converted for any reason.
+  # This method can be used to check if an argument is an array.
+  #
+  #    Array.try_convert([1])   #=> [1]
+  #    Array.try_convert("1")   #=> nil
+  #
+  #    if tmp = Array.try_convert(arg)
+  #      # the argument is an array
+  #    elsif tmp = String.try_convert(arg)
+  #      # the argument is a string
+  #    end
+  #
+  def self.try_convert(obj)
+    if obj.respond_to?(:to_ary)
+      obj.to_ary
+    else
+      nil
+    end
+  end
+
   ##
   # call-seq:
   #    ary.uniq!                -> ary or nil
@@ -709,4 +734,14 @@ class Array
     end
     nil
   end
+
+  ##
+  #  call-seq:
+  #     ary.to_ary -> ary
+  #
+  #  Returns +self+.
+  #
+  def to_ary
+    self
+  end
 end

mrbgems/mruby-array-ext/test/array.rb

 ##
 # Array(Ext) Test
 
+assert("Array.try_convert") do
+  assert_nil Array.try_convert(0)
+  assert_nil Array.try_convert(nil)
+  assert_equal [], Array.try_convert([])
+  assert_equal [1,2,3], Array.try_convert([1,2,3])
+end
+
 assert("Array#assoc") do
   s1 = [ "colors", "red", "blue", "green" ]
   s2 = [ "letters", "a", "b", "c" ]
@@ -298,3 +305,8 @@ assert("Array#index (block)") do
   assert_nil (1..10).to_a.index { |i| i % 5 == 0 and i % 7 == 0 }
   assert_equal 34, (1..100).to_a.index { |i| i % 5 == 0 and i % 7 == 0 }
 end
+
+assert("Array#to_ary") do
+  assert_equal [], [].to_ary
+  assert_equal [1,2,3], [1,2,3].to_ary
+end

mrbgems/mruby-hash-ext/mrblib/hash.rb

@@ -60,6 +60,25 @@ class Hash
     h
   end
 
+  ##
+  # call-seq:
+  #     Hash.try_convert(obj) -> hash or nil
+  #
+  # Try to convert <i>obj</i> into a hash, using to_hash method.
+  # Returns converted hash or nil if <i>obj</i> cannot be converted
+  # for any reason.
+  #
+  #     Hash.try_convert({1=>2})   # => {1=>2}
+  #     Hash.try_convert("1=>2")   # => nil
+  #
+  def self.try_convert(obj)
+    if obj.respond_to?(:to_hash)
+      obj.to_hash
+    else
+      nil
+    end
+  end
+
   ##
   # call-seq:
   #     hsh.merge!(other_hash)                                 -> hsh

mrbgems/mruby-hash-ext/test/hash.rb

@@ -39,6 +39,12 @@ assert('Hash.[] "c_key", "c_value"') do
   end
 end
 
+assert('Hash.try_convert') do
+  assert_nil Hash.try_convert(nil)
+  assert_nil Hash.try_convert("{1=>2}")
+  assert_equal({1=>2}, Hash.try_convert({1=>2}))
+end
+
 assert('Hash#merge!') do
   a = { 'abc_key' => 'abc_value', 'cba_key' => 'cba_value' }
   b = { 'cba_key' => 'XXX',  'xyz_key' => 'xyz_value' }

mrbgems/mruby-string-ext/mrblib/string.rb

 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

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]