1 files changed, 19 insertions, 1 deletions
diff --git a/lib/slop/option.rb b/lib/slop/option.rb
index 093b37f..655b283 100644
--- a/lib/slop/option.rb
+++ b/lib/slop/option.rb
@@ -56,7 +56,11 @@ module Slop
           raise Slop::MissingArgument.new("missing argument for #{flag}", flags)
         end
       else
-        @value = call(value)
+        if validate_type? && !valid?(value) && !suppress_errors?
+          raise Slop::InvalidOptionValue.new("invalid value for #{flag}", flags)
+        end
+
+        @value = valid?(value) && call(value)
       end
 
       block.call(@value) if block.respond_to?(:call)
@@ -107,6 +111,13 @@ module Slop
       config[:required]
     end
 
+    # Returns true if an exception should be raised when this option value can't
+    # be parsed into the desired type or does not conform to the expected type's
+    # format
+    def validate_type?
+      config[:validate_type] || config[:validate_types]
+    end
+
     # Returns all flags joined by a comma. Used by the help string.
     def flag
       flags.join(", ")
@@ -119,6 +130,13 @@ module Slop
       key.to_sym
     end
 
+    # Override this if you want to provide a custom validator for a type. This
+    # method must return whether the provided value is valid for the current
+    # argument's type
+    def valid?(value)
+      true
+    end
+
     # Returns true if this option should be displayed with dashes transformed into underscores.
     def underscore_flags?
       config[:underscore_flags]