Added ActiveSupport::Inflector.safe_constantize and String#safe_constantize; refactored common constantize tests into ConstantizeTestCases

2 files changed, 43 insertions, 3 deletions

diff --git a/activesupport/lib/active_support/core_ext/string/inflections.rb b/activesupport/lib/active_support/core_ext/string/inflections.rb
index 002688d6c0..b4218cb42c 100644
--- a/activesupport/lib/active_support/core_ext/string/inflections.rb
+++ b/activesupport/lib/active_support/core_ext/string/inflections.rb
@@ -33,14 +33,27 @@ class String
 
   # +constantize+ tries to find a declared constant with the name specified
   # in the string. It raises a NameError when the name is not in CamelCase
-  # or is not initialized.
+  # or is not initialized.  See ActiveSupport::Inflector.constantize
   #
   # Examples
-  #   "Module".constantize # => Module
-  #   "Class".constantize  # => Class
+  #   "Module".constantize       # => Module
+  #   "Class".constantize        # => Class
+  #   "blargle".safe_constantize # => NameError: wrong constant name blargle
   def constantize
     ActiveSupport::Inflector.constantize(self)
   end
+  
+  # +safe_constantize+ tries to find a declared constant with the name specified
+  # in the string. It returns nil when the name is not in CamelCase
+  # or is not initialized.  See ActiveSupport::Inflector.safe_constantize
+  #
+  # Examples
+  #   "Module".safe_constantize  # => Module
+  #   "Class".safe_constantize   # => Class
+  #   "blargle".safe_constantize # => nil
+  def safe_constantize
+    ActiveSupport::Inflector.safe_constantize(self)
+  end
 
   # By default, +camelize+ converts strings to UpperCamelCase. If the argument to camelize
   # is set to <tt>:lower</tt> then camelize produces lowerCamelCase.
diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index 423b5abd20..b22e39c7c2 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -224,6 +224,33 @@ module ActiveSupport
       end
     end
 
+    # Tries to find a constant with the name specified in the argument string:
+    #
+    #   "Module".safe_constantize     # => Module
+    #   "Test::Unit".safe_constantize # => Test::Unit
+    #
+    # The name is assumed to be the one of a top-level constant, no matter whether
+    # it starts with "::" or not. No lexical context is taken into account:
+    #
+    #   C = 'outside'
+    #   module M
+    #     C = 'inside'
+    #     C                    # => 'inside'
+    #     "C".safe_constantize # => 'outside', same as ::C
+    #   end
+    #
+    # nil is returned when the name is not in CamelCase or the constant is
+    # unknown.
+    #
+    #   "blargle".safe_constantize  # => nil
+    def safe_constantize(camel_cased_word)
+      begin
+        camel_cased_word.constantize
+      rescue NameError
+        nil
+      end
+    end
+    
     # Turns a number into an ordinal string used to denote the position in an
     # ordered sequence such as 1st, 2nd, 3rd, 4th.
     #