Suspending event firing

Question

Hi Everyone....
I have a series of segmented controls on my panel. I have set the default to be all segment 2 to be the value at design time.
Now when i populate the controls with the value from the database, the event for segment changed gets fired.
I would like to suspend the segment changed event until after i load the form with data.
Is this possible and how do i do it?
thanks
tony

Answer 1

Hi Tony -
Based on some of your recent posts, I'm assuming your question is about UISegmentedControl in the iPhone SDK. Though the corresponding AppKit control is similar in many ways, I haven't considered NSSegmentedControl in this response.
alt-088 wrote:
... when i populate the controls with the value from the database, the event for segment changed gets fired.
I'm not sure I know what you mean by "populate the controls". Do you mean setting the title of each segment? I don't think a programmatic change in the title should be generating a UIControlEventValueChanged event. In general, controls only send action messages in response to a user action--in this case a tap on one of the segments.
Do you mean the user is tapping one or more segments before the data is finished loading? In that case it might be best to disable all the controls until the program is ready to handle a touch event. If the data load takes a noticeable amount of time, I think the user might be confused if the response to a tap were delayed.
I would like to suspend the segment changed event until after i load the form with data.
Is this possible and how do i do it?
Yes, there are lots of ways you could do that. For example, you could maintain a boolean ivar to indicate whether a new data load was required or in progress. Each action method could test that ivar and if the data wasn't ready, the method would set an actionPending ivar instead of completing the action. When the data was ready, any pending actions would be handled. If necessary, 'actionPending' could be an array containing the address of each UISegmentControl which had fired before or during the load. E.g.:
- (IBAction)segmentChanged:(id)sender {
if (self.dataReady == NO) {
[self.actionPending addObject:sender];
else {
UISegmentedControl *control = sender;
int tag = control.tag;
int segment = control.selectedSegmentIndex;
// do something based on tag and segment
- (void)dataIsReady {
self.dataReady = YES;
for (UISegmentControl *control in actionPending) {
[self segmentChanged:control];
[actionPending removeAllObjects];
Note if any of the segment controls is momentary, you'll need to store more data in actionPending since control.selectedSegmentIndex is only valid during the event cycle started by a segment tap.
Once again, I question the need for a delayed response to segment taps. But if that's what you really want, something like the above example should work for you.
- Ray