Add custom "finish" method for options

3 files changed, 19 insertions, 2 deletions

diff --git a/lib/slop/option.rb b/lib/slop/option.rb
index a624110..9c11080 100644
--- a/lib/slop/option.rb
+++ b/lib/slop/option.rb
@@ -1,6 +1,7 @@
 module Slop
   class Option
     attr_reader :flags, :desc, :config, :count
+    attr_writer :value
 
     def initialize(flags, desc, **config)
       @flags  = flags
@@ -24,11 +25,17 @@ module Slop
       @value = call(value)
     end
 
-    def call(value)
+    def call(_value)
       raise NotImplementedError,
         "you must override the `call' method for option #{self.class}"
     end
 
+    # By default this method does nothing. It's called when all options
+    # have been parsed and allows you to mutate the `@value` attribute
+    # according to other options.
+    def finish(_result)
+    end
+
     def value
       @value || config[:default]
     end
diff --git a/lib/slop/parser.rb b/lib/slop/parser.rb
index 0ef4931..ef31ee1 100644
--- a/lib/slop/parser.rb
+++ b/lib/slop/parser.rb
@@ -30,7 +30,9 @@ module Slop
         end
       end
 
-      Result.new(self)
+      Result.new(self).tap do |result|
+        used_options.each { |o| o.finish(result) }
+      end
     end
 
     def unused_options
diff --git a/lib/slop/result.rb b/lib/slop/result.rb
index 5dd5213..0d0a3ab 100644
--- a/lib/slop/result.rb
+++ b/lib/slop/result.rb
@@ -27,6 +27,14 @@ module Slop
       end
     end
 
+    def used_options
+      parser.used_options
+    end
+
+    def unused_options
+      parser.unused_options
+    end
+
     # Returns a hash with option key => value.
     def to_hash
       Hash[options.map { |o| [o.key, o.value] }]