Design patterns for enabling user interface elements based on user permissions?

Question

We have a web application and its front end is implemented with GWT/GXT. Users can belong to various groups and these groups can then have various permissions. The permissions are quite fine grained, for example comment_create, comment_edit, comment_delete and comment_read.

What would be the best way to enable and disable user interface controls based on user permissions? We have an utility method that returns boolean value with given user and permission name. But at the moment each control is wrapped inside if clause and that makes the code bit messy.

Answer 1

I'm not sure how you'd implement this in GWT/GXT, but the old MFC way of enabling menus might be a place to start.

This had a separate ON_UPDATE_COMMAND_UI message which you gave a menu id and method name. The method would be called and you could enable or disable that menu option depending on your logic. In your case it would be based on the user id. This is on a per menu id basis and is therefore as fine grained as you need it to be.

Answer 2

See the decorator pattern.