lib/promise.rb in promise-0.2.1 vs lib/promise.rb in promise-0.3.0

@@ -41,29 +41,47 @@
   # Force the evaluation of this promise immediately
   #
   # @return [Object]
   def __force__
     @mutex.synchronize do
-      if @result.equal?(NOT_SET) && @error.equal?(NOT_SET)
+      if !__forced?
         begin
           @result = @block.call
         rescue ::Exception => e
           @error = e
         end
       end
-    end if @result.equal?(NOT_SET) && @error.equal?(NOT_SET)
+    end unless __forced?
     # BasicObject won't send raise to Kernel
     @error.equal?(NOT_SET) ? @result : ::Kernel.raise(@error)
   end
   alias_method :force, :__force__
 
   ##
   # Does this promise support the given method?
   #
   # @param  [Symbol]
-  # @return [Boolean]
+  # @return [true, false]
   def respond_to?(method)
-    :force.equal?(method) || :__force__.equal?(method) || __force__.respond_to?(method)
+    :__forced?.equal?(method) || :force.equal?(method) || :__force__.equal?(method) || __force__.respond_to?(method)
+  end
+
+  ##
+  # Returns true if klass.equal?(Promise) or the underlying block returns an
+  # instance of the given klass
+  #
+  # @param [Class]
+  # @return [true, false]
+  def is_a?(klass)
+    klass.equal?(::Promise) || __force__.is_a?(klass)
+  end
+
+  ##
+  # Returns true if this promise has finished executing
+  #
+  # @return [true, false]
+  def __forced?
+    !(@result.equal?(NOT_SET) && @error.equal?(NOT_SET))
   end
 
   private
 
   def method_missing(method, *args, &block)