Updated comments, added before_destroy where applicable

app/controllers/ingredients_controller.rb

@@ -43,7 +43,6 @@ class IngredientsController < ApplicationController
   end
 
   def destroy
-    # FIXME: don't destroy if any meal depend on ingredient
     if @ingredient.destroy
       flash[:notice] = 'Deleted ingredient'
     end

app/controllers/measurements_controller.rb

@@ -39,7 +39,6 @@ class MeasurementsController < ApplicationController
   end
 
   def destroy
-    # FIXME: don't destroy if there are any readout values
     if @measurement.destroy
       flash[:notice] = 'Deleted measurement'
     end

app/controllers/sources_controller.rb

@@ -22,7 +22,6 @@ class SourcesController < ApplicationController
   end
 
   def destroy
-    # FIXME: do not destroy if anything depends on it
     if @source.destroy
       flash[:notice] = 'Deleted source'
     end

app/controllers/units_controller.rb

@@ -22,7 +22,6 @@ class UnitsController < ApplicationController
   end
 
   def destroy
-    # FIXME: do not destroy if anything depends on it
     if @unit.destroy
       flash[:notice] = 'Deleted unit'
     end