 <p>Ok i think i understand your problem :</p> <p>The after_destroy method in PictureFileCallbacks will be auto-magically called by rails :</p> <p>When rails destroys your PictureFile object, it will instantiate a PictureFileCallbacks object and try to run an after_destroy method in it.</p> <p>Everything works by convention, if you follow the naming properly everything will work out of the box.</p> <p>Try it on a dummy project, and if you have some trouble making this work come back with some code to show.</p>