Question

I’m trying to write code to draw a clock on the screen of an iOS device. I need to get the angle of a line (seconds, minutes, hours hands of clock) from the current time. My code accurately grabs the time, but for some reason, all of the angles I receive end up being the same (no matter what time it is).

If it helps, the angle I am constantly receiving is:

-1.5707963267948966

Here is the code I use to get the angles:

secondsTheta = ((seconds/60) * (2 * M_PI)) - (M_PI / 2);
minutesTheta = ((minutes/60) + (seconds/3600)) * (2 * M_PI) - (M_PI / 2);
hoursTheta = ((hours/12) + (minutes/720) + (seconds/43200)) * (2 * M_PI) - (M_PI / 2);

My thought is that something is funky with M_PI, but I don’t know what would be…but as I said, the seconds, minutes, and hours variables are correct. They are declared in my header file as ints, and I know that [NSDateComponents seconds](etc) returns an NSInteger, but I don’t think that should matter for this basic math.

Answer 1

Your seconds, minutes and hours are ints. Dividing ints by ints does integer arithmetic and truncates the values, so

seconds/60

will always give you 0. Objective C inherits this behavior from C and this is fairly common behavior among programming languages.