iOS: more basics

Random numbers
random() // gives you 0-(2^31-1)
to generate random number from 0 to 9: random() % 10
3 to 18: random() % ( 18-3 +1) + 3

if need numeric pad for textfield, interface builder > text input trait > num pad

Timer
NSTimer
[NSTimer timerWithTimeInterval:0.5 /* seconds */ invocation: invocation repeats:YES]

NSDate
NSDate *now = [[NSDate alloc] init];
[date2 timeIntervalSinceDate:date1]; returns seconds
[date1 release];