Question

I am getting tricked up with arrays and nested arrays.

I would like this if statement to evaluate to True if lastObject doesn’texist, or if accelerometer.x – lastObject[0] > .1

My code doesn’t do this.

if (![accelerometerArray lastObject] || 
  [NSNumber numberWithDouble:acceleration.x] - 
  [[accelerometerArray lastObject] objectAtIndex: 0] > [NSNumber numberWithDouble:.1) 
 {

  NSArray *entry = [[NSArray alloc] initWithObjects:
                    [NSNumber numberWithDouble:acceleration.x],
                    [NSNumber numberWithDouble:acceleration.y],
                    [NSNumber numberWithDouble:acceleration.z], 
                    [NSDate date]];

  [accelerometerArray addObject: entry];
  [entry release];
}

Answer 1

you’re missing a closing “]” on “[NSNumber numberWithDouble:.1” and i think you may need to write it like:

[[NSNumber numberWithDouble:acceleration.x] doubleValue] –
[[[accelerometerArray lastObject] objectAtIndex: 0] doubleValue] > 0.1)

i think you can swap out “[NSNumber numberWithDouble:.1]” with 0.1 too.