iOS 日期转string

+(NSString*)dateStringWithDate:(NSDate *)date andFomatter:(NSString *)fomatter
{
    
    NSDateFormatter * dateF = [[NSDateFormatter alloc] init];
    dateF.dateFormat = fomatter;
    if([dateF stringFromDate:date].length > 0)
        return [dateF stringFromDate:date];
    dateF.dateFormat = @"yyyy-MM-dd";
    return [dateF stringFromDate:date];
}