Question

In the following code, I’m creating a category on UIColor to create a random color. However, from this code, I would have thought that the ‘if’ conditional would be true every time the method is run, instead of just the first time.

I think I’m not really understanding static variables correctly. Does a static variable only get set once, and then the second time the method is run, that line is just ignored? (so seeded would forever be YES after the first run)?

@interface UIColor(Random) +(UIColor *)randomColor {     static BOOL seeded = NO;     if (!seeded)      {         seeded = YES;         srandom(time(NULL));     }     CGFloat red = (CGFloat)random()/(CGFloat)RAND_MAX;     CGFloat green = (CGFloat)random()/(CGFloat)RAND_MAX;     CGFloat blue = (CGFloat)random()/(CGFloat)RAND_MAX;     return [UIColor colorWithRed:red green:green blue:blue alpha:1.0f]; } 

Answer 1

You are correct that the static variable only is set once.

the code

static BOOL seeded = NO; 

is not equivalent to

static BOOL seeded; seeded = NO; 

the second one would always evaluate to NO, while the first one will evaluate to NO until set differently.