What this means is that you can increase your method performance by declaring variable only once and reuse it when needed next time.
Here's example code:
+ (NSString *)numberAsString:(NSUInteger *)aNumberIf you move static variable definition outside of all methods, it will be available for everyone within the class. This is the "normal" use case for static variables.
static NSArray *myNumbers = nil;
myNumbers = [[NSArray alloc] initWithObjects:
return [myNumbers objectAtIndex:aNumber];