Professional Adobe® Flex® 3

Chapter 57. Advanced Data Management Services

This chapter supplements the previous chapter on the Data Management Service (DMS) by providing a collection of tips for working with lazy associations, overcoming item-pending errors, and managing user-specific data.

Overview of DMS

There are a great many ways to use the DMS, and these possibilities can sometimes be overwhelming. From evaluating the relative merits of lazy and eager associations to choosing from the multitude of channels and end points available for communication, and making best use of the client and server-side libraries, there are some pitfalls to be avoided along the way.

This chapter covers three topics relevant for many DMS projects. These are lessons learned in the field that may not be covered in the official documentation.

• Summary-to-Details Modeling — It is common to provide users with a lists of summary information before allowing them to view the full details of one item at a time. There are various ways to achieve this using LCDS, but there are some subtle yet important differences in the outcome.

• Overcoming Item-Pending Errors — The null object errors of LCDS are handled transparently in MXML bindings but require special attention in ActionScript code. There's a simple technique for enclosing a function that may raise item-pending errors and calling it repeatedly until all the pending items have been fetched.

• Managing Shared and User-Specific Data — LCDS makes it easy to synchronize data among users, but sometimes ...