To open a Rails application in TextMate select the application and choose Open App in TextMate from the Application menu. This opens a hierarchical view of the application in a TextMate window. (If you're not familiar with it, TextMate is a popular commercial text editor for working with Ruby source code.)
If you want to open just the source code for a particular table, select the table then choose Open Table Code in TextMate from the Table menu. This opens just the source files associated with this particular table.
To directly access the files in a Rails application choose Reveal in Finder from the Application menu.
