Update picker data in mainViewController

Question

Hi,
In my app, the mainViewControl uses a UIPickerView. The UIPicker view is populated by a NSMutableArray. The mainVV lets the user make a choice of selecting an Item in the picker. Based on the choice, the actions in the mainVC are Add/Delete/Update. The mainViewController calls the appropriate add/delete/update method in the Item class, that manipulates the SQLite database underneath (thru ManageDB class).
mainVC ------------------> Item --------------- --> ManageDB
|
+---> Picker (array) <---populated by [Item populate] method;
|
+---add/delete/update : [Item methods] change the database using [ManageDB methods]
|
+---need to update Picker
I am not sure of the timing of the events : I see that the control returns to mainVC from the methods in Item class before the methods in ManageDB (called from Item class) have finished - therefore, I cannot update the picker contents.
How can the mainVC know when the methods in ManageDB have finished? If I can know that, the repopulation (by re-reading the DB) will be easy.
Thx - Sam.

Answer 1

I added code to use NSNotification class. I added the observer in the mainVC and used postNotification in the Item class. But then I got the following:
[Session started at 2010-10-23 23:30:27 -0700.]
GNU gdb 6.3.50-20050815 (Apple version gdb-1469) (Wed May 5 04:36:56 UTC 2010)
Copyright 2004 Free Software Foundation, Inc.
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This GDB was configured as "x86_64-apple-darwin".sharedlibrary apply-load-rules all
Attaching to process 12571.
Pending breakpoint 8 - ""ManageDB.m":108" resolved
Pending breakpoint 9 - "objcexceptionthrow" resolved
Pending breakpoint 10 - "*0x0256a5be" resolved
Data Formatters temporarily unavailable, will re-try after a 'continue'. (Not safe to call dlopen at this time.)
The code is as following:
mainVC.m:
- (void)viewDidLoad {
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(receiveNotification:)
name:@"addItemFinished"
object:nil];
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self
name:@"addItemFinished"
object:nil];
Item.m:
- (void)addItem {
[[NSNotificationCenter defaultCenter] postNotification:
[NSNotification notificationWithName:@"addItemFinished" object:self]];
PS: If I comment out the NSNotification related code, the error is not generated.