Add String#ascii_only.

lib/core/facets/string/ascii_only.rb

@@ -0,0 +1,52 @@
+class String
+  # Get a new string with non-ASCII characters removed.
+  #
+  # alt - String to replace non-ASCII characters with.
+  #       Defaults to a blank string (`''`).
+  #
+  # Examples
+  #
+  #   'abc'.ascii_only     #=> 'abc'
+  #   '中文123'.ascii_only  #=> '123'
+  #
+  # Returns a copy of [String] with ASCII characters only.
+  #
+  # CREDIT: Nathan Long
+  #
+  # SEE: http://stackoverflow.com/questions/1268289
+  def ascii_only(alt='')
+    encoding_options = {
+      :invalid                     => :replace,  # Replace invalid byte sequences
+      :undef                       => :replace,  # Replace anything not defined in ASCII
+      :replace                     => alt,       # Use a blank for those replacements
+      :UNIVERSAL_NEWLINE_DECORATOR => true       # Always break lines with \n
+    }
+    self.encode(Encoding.find('ASCII'), encoding_options)
+  end
+
+  # Modify string keeping only ASCII characters.
+  #
+  # alt - String to replace non-ASCII characters with.
+  #       Defaults to a blank string (`''`).
+  # 
+  # Examples
+  #
+  #   'abc'.ascii_only!     #=> 'abc'
+  #   '中文123'.ascii_only!  #=> '123'
+  #
+  # Returns [String]
+  #
+  # CREDIT: Nathan Long
+  #
+  # SEE: http://stackoverflow.com/questions/1268289
+  def ascii_only!(alt='')
+    encoding_options = {
+      :invalid                     => :replace,  # Replace invalid byte sequences
+      :undef                       => :replace,  # Replace anything not defined in ASCII
+      :replace                     => alt,       # Use a blank for those replacements
+      :UNIVERSAL_NEWLINE_DECORATOR => true       # Always break lines with \n
+    }
+    self.encode!(Encoding.find('ASCII'), encoding_options)
+  end
+
+end

test/core/string/test_ascii_only.rb

@@ -0,0 +1,30 @@
+covers 'facets/string/ascii_only'
+
+test_case String do
+
+  method :ascii_only do
+    test 'without any non-ascii' do
+      'abc'.ascii_only.assert == 'abc'
+    end
+
+    test 'with non-ascii' do
+     '中文123'.ascii_only.assert == '123'
+    end
+  end
+
+  method :ascii_only! do
+    test 'without any non-ascii' do
+      s = 'abc'
+      s.ascii_only!
+      s.assert == 'abc'
+    end
+
+    test 'with non-ascii' do
+      s = '中文123'
+      s.ascii_only!
+      s.assert == '123'
+    end
+  end
+
+end
+