Drag and drop is also useful for invoking an action or actions on a dropped object. The Drag and Drop Action is a common pattern. Its most familiar example is dropping an item in the trash to perform the delete action.
Normally uploading files to a web application includes pressing the upload button and browsing for a photo. This process is repeated for each photo.
When Yahoo! Photos was relaunched in 2006, it included a drag and drop upload feature. It allowed the user to drag photos directly into the upload page. The drop signified the upload action (Figure 2-30).
Figure 2-30. Yahoo! Photos provided a way to upload files directly to the site via drag and drop from the user's filesystem into the web page
This is not a trivial implementation. But it does clearly illustrate the benefit of drag and drop for operating on a set of files. The traditional model requires each photo to be selected individually for upload. Drag and drop frees you to use whatever browsing method is available on your system and then drop those photos for upload.
Unfortunately, drag and drop can sometimes drive the design of an interface instead of being an extension of a natural interface. These interactions are almost always doomed, as they are the tail wagging the proverbial dog. Rating movies, books, and music is a common feature found ...