ios - 将变量传递给类/实例的最佳方法？

Question

我有一个实例，它根据一年中的哪一天返回地球与太阳的距离。因为它在内部计算今天的日期，所以它是独立的。但我想改变它，所以我将它作为整数传递一年中的某一天。最好的方法是什么？我有什么选择吗？

-(double) calculateDistranceFromSun
{
    // Calculate Day of the Year
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSUInteger dayOfYear = [gregorian ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:[NSDate date]];
    setDayOfYear = dayOfYear;
     // Source: curious.astro.cornell.edu/question.php?number=582
    double Rad2Deg       = Pi/180;
    double Theta         = (dayOfYear/(DaysInYear/360)*Rad2Deg);
    double CC            = cos(Theta);
    setDistanceFromSun   = SemiMajorAxis*(1-pow(Eccentricy,2))/(1+Eccentricy*CC);
    return setDistanceFromSun;
}

Answer 1

-(double) calculateDistranceFromSunWithDate:(NSDate *)date
{
    // Calculate Day of the Year
    NSUInteger dayOfYear = [gregorian ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:date];
    setDayOfYear = dayOfYear;
     // Source: curious.astro.cornell.edu/question.php?number=582
    double Rad2Deg       = Pi/180;
    double Theta         = (dayOfYear/(DaysInYear/360)*Rad2Deg);
    double CC            = cos(Theta);
    setDistanceFromSun   = SemiMajorAxis*(1-pow(Eccentricy,2))/(1+Eccentricy*CC);
    return setDistanceFromSun;
}