iOS 获取时间戳 10位(秒级)，13位(毫秒级)

#pragma mark - 获取时间戳:10位，秒级
- (NSString *)tenCharactersTimeStamp {
    // iOS默认生成的时间戳是10位，秒级
    NSTimeInterval time = [[NSDate date] timeIntervalSince1970];
    NSString *timeStamp = [NSString stringWithFormat:@".f",time];
    
    return timeStamp;
}

#pragma mark - 获取时间戳:13位，毫秒级
- (NSString *)thirteenCharactersTimeStamp {
    // 设置日期格式
    NSDateFormatter * formatter = [[NSDateFormatter alloc ] init];
    [formatter setDateFormat:@"yyyy-MM-dd hh:mm:ss.SSS"];
    
    NSString *dateStr =  [formatter stringFromDate:[NSDate date]];
    NSDate *date = [formatter dateFromString:dateStr];
    
    NSTimeInterval time = [date timeIntervalSince1970]*1000;
    NSString *timeStamp = [NSString stringWithFormat:@".f",time];
    
    return timeStamp;
}