Change the text in a NSTextField programmatically?

You should be able to use the setStringValue: method that NSTextField inherits from NSControl.

The full signature is:

- (void)setStringValue:(NSString *)aString

This will work:

[field setStringValue:[NSString stringWithFormat:@"%i",number]];

If it doesn't do anything, it probably means field isn't set to point to the field (e.g. by making a connection in Interface Builder).