<分区>
哪个是首选方法？假设 myInteger 99.99% 的时间将具有有效值，并且此方法将被非常快速地调用。
-(BOOL)validDate
{
NSUInteger myInteger = ...//method to obtain value;
if (myInteger != NSNotFound)
return YES;
return NO;
}
-(BOOL)validDate
{
NSUInteger myInteger = ...//method to obtain value;
if (myInteger == NSNotFound)
return NO;
return YES;
}