Previously we looked at the new ColdFusion 8 data grid and how to populate that control using asynchronous calls back to a ColdFusion Component. In that example the CFC contained a single method that returned a page of data as requested by the data grid.
Like the previous incarnations of , the new Ajax enabled HTML grid allows data to be updated right within the grid. When the is used in edit mode, column values may be edited as needed, and rows may be deleted. Unfortunately, the current implementation of the HTML does not support inserting new rows. This is a pretty serious limitation, and one that we’ll hopefully address in the future – for now you’ll need to use another form to add new rows.
You will recall that requests data as needed by making calls to a CFC method specified in the bind attribute. To process edits a second CFC method is needed, and it must be passed to the onchange attribute. Here is a modified that supports data editing:
There are three changes in this (compared to the grid created previously). First of all, selectmode=”edit” puts the data grid in edit mode. This allows editing, but not deleting. To allow rows to be deleted, delete=”yes” is also specified. And finally, a CFC method is specified in the onchange attribute. When invoked (upon an edit or a delete) three arguments will be passed, the action (U for update or D for delete), the row being changed, and the changes (only populated for updates, and not for deletes).
The specified CFC has to accept these three arguments, and returns no data. Within the CFC you can use tags (or perform any other operations) to actually perform the updates. Here’s an example:
UPDATE artists
SET #colname# = '#value#'
WHERE artistid = #ARGUMENTS.gridrow.artistid#
DELETE FROM artists
where artistid = #ARGUMENTS.gridrow.artistid#
The code uses a to process a gridaction of U (update) or D (delete). For updates, argument gridchanged will be a structure containing an element for each column changed, the element name is the column name and the element value is the new value. Each column is updated individually, if a user makes three edits to the same row in the data grid the this method will be called three times, once for each row. As such, for updates, gridchanged only ever contains a single element, and so the code extracts the column name and value and saves them to local variables. These variables are then used in a to perform the actual update, using the primary key in the passed row (ARGUMENTS.gridrow) for the SQL WHERE clause. Deletes are processed similarly, with only the primary key needed.
Here is the complete artists.cfc, with both the bind and onchange methods:
SELECT artistid, lastname, firstname, email
FROM artists
ORDER BY #ARGUMENTS.gridsortcolumn# #ARGUMENTS.gridsortdir#
UPDATE artists
SET #colname# = '#value#'
WHERE artistid = #ARGUMENTS.gridrow.artistid#
DELETE FROM artists
WHERE artistid = #ARGUMENTS.gridrow.artistid#
We’ll look at additional examples in the future.
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