iOS关于NSCalendar的使用

由于最近项目需要，关于VIP截止时间的处理：项目需求时这样的：支付完成之后在某个界面上显示VIP的截止时间，VIP的时间是一个月，下面是代码

static NSString *const limitDate = @"limitDate";
static NSString *const formatPaymentTime = @"formatPaymentTime";

/**
 *  保存截止时间
 *
 *  @param paymentTime 支付时间
 *
 *  @return 截止时间
 */
+ (NSString *)persistLimitTime:(NSString *)paymentTime{
    
    //加这一句的目的是因为在支付时候本地的时间格式是下面的样子，
    //由于项目需求要用到YYYY-MM-dd这种格式
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"YYYYMMddHHmmss"];
    
    NSDate *currentPayTime = [formatter dateFromString:paymentTime];
    
    NSDate *recordDate = [[NSUserDefaults standardUserDefaults] objectForKey:limitDate];
    
    
    [formatter setDateFormat:@"YYYY-MM-dd"];
    
    formatter.timeZone = [NSTimeZone defaultTimeZone];
    
    NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    
    //时间比较，这个目的是有可能续费，截至时间需要叠加
    if (recordDate) {
        NSComparisonResult result = [calender compareDate:currentPayTime toDate:recordDate toUnitGranularity:NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay];
        if (result==NSOrderedAscending) {
            currentPayTime = recordDate;//截止时间大于当前支付时间
            
        }
    }
    
    //加一个月，VIP 周期
    NSDateComponents *monthComponent = [[NSDateComponents alloc] init];
    [monthComponent setMonth:+1];
    [monthComponent setYear:0];
    [monthComponent setDay:0];
    
    NSDate *toDate = [calender dateByAddingComponents:monthComponent toDate:currentPayTime options:0];
    
    NSDateComponents *component = [calender components:NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:toDate];
    
    NSDate *dateNew = [calender dateFromComponents:component];
    
    paymentTime = [formatter stringFromDate:dateNew];
    
    
    [[NSUserDefaults standardUserDefaults] setObject:dateNew forKey:limitDate];
    [[NSUserDefaults standardUserDefaults] setObject:paymentTime forKey:formatPaymentTime];
    [[NSUserDefaults standardUserDefaults] synchronize];
    
    return paymentTime;
}

/**
 *  判断VIP是否过期
 *
 *  @return YES:过期/NO:没过期
 */
+ (BOOL)isExpried{
    
    NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDate *recordDate = [[NSUserDefaults standardUserDefaults] objectForKey:limitDate];
    
    //时间比较
    if (recordDate) {
        NSComparisonResult result = [calender compareDate:[NSDate date] toDate:recordDate toUnitGranularity:NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay];
        return result==NSOrderedDescending?YES:NO;
        
    }
    return YES;
    
}