Events in Cocoa

Question

Is there a way to handle events in Cocoa. I am a .Net programmer trying to come over from the dark side but as of right now I am stuck on what seems to be a simple problem. I've created a simple water meter program. It is composed of two NSTextFields, a NSButton, and a NSMessageLabel. It takes input from the one text field subtracts it from the other then mutiplies that number by the 'price per gallon' and displays the result in the label. Seems simple enough. I am now trying to clear the label when the user changes either one of those numbers in the TextFields. I've searched online but only been able to find that I might need to use delegates but only maybe, and that I might need to use control?TextDidChange. If anyone could help me or point me in the right direction i would greatly appreciate it.
Thomas

Answer 1

I put the log statement in my -awakeFromNib and I see in the console window where the log message appears, but the textDidChange is not getting called, or at least not working because neither the log message nor the the clearing of the message box. Here is my implementation file :
[i]
#import "WaterMeterController.h"
@implementation WaterMeterController
-(void)awakeFromNib
NSLog(@"awakeFromNib called");
[currentReading setDelegate:self];
[previousReading setDelegate:self];
     //Variable Declaration
     double PRICE_PER_GALLON = .0075;
       double totalBill = 0.0;
     int galUsed = 0;
     int currentBox = 0;
     int previousBox = 0;
- (IBAction)calculateBill:(id)sender
     currentBox = [currentReading intValue];
     previousBox = [previousReading intValue];
     galUsed = currentBox - previousBox;
     totalBill = PRICE_PER_GALLON * galUsed;
     NSString *theBill;
     theBill = [NSString stringWithFormat: @" %lf", totalBill];
     [messageText setStringValue: theBill];
- (void)textDidChange:(NSNotification *)aNotification
     //Log to console:
     NSLog(@"TextChanged");
     //Clear the Text
    [messageText setStringValue:@""];
@end
[/i]
I have also made both my text boxes (currentReading, and previousReading) delegates in the .Nib file by control clicking from the text boxes to the controller class. I can't see why this isn't working
Thanks for looking
Thomas