过滤/子集/删除包含R中字符串中间字符的行(filter/subset/delete rows that contain character in middle of string in R)

 NSDate本身不能用JSON表示。 正如NSJSONSerialization文档所说： 
 
 
 
 可以转换为JSON的对象必须具有以下属性： 
 
 
 
  
 顶级对象是NSArray或NSDictionary 。 
 
  
 所有对象都是NSString ， NSNumber ， NSArray ， NSDictionary或NSNull 。 
 
  
 所有字典键都是NSString实例。 
 
  
 数字不是NaN或无穷大。 
 
 
 
 
 从您的问题中不清楚日期应该以什么格式表示在您的JSON中。 通常，您以某种标准日期字符串格式格式化日期（例如ISO 8601 / RFC 3339格式，如2016-01-25T06:54:00Z ）。 
 
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.locale = [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"];
formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
formatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ssZZZZZ";
 
 或者，对于macOS 10.12和iOS 10，您可以： 
 
NSISO8601DateFormatter *formatter = [[NSISO8601DateFormatter alloc] init];
 
 然后： 
 
NSString *birthDateString = [formatter stringFromDate:birthDate];
 
 有关详细信息，请参阅Apple技术问答1480 。 
 
 或许，因为这是生日，你只需要yyyy-MM-dd 。 
 
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.locale = [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"];
formatter.dateFormat = @"yyyy-MM-dd";
NSString *birthDateString = [formatter stringFromDate:birthDate];
 
 最重要的是，您必须告诉我们您的Web服务期望格式化日期的格式，然后我们可以帮助您相应地格式化它。 

NSDate cannot be represented in JSON natively. As NSJSONSerialization documentation says:
 
 
 
An object that may be converted to JSON must have the following properties:
 
 
 
  
The top level object is an NSArray or NSDictionary.
 
  
All objects are instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.
 
  
All dictionary keys are instances of NSString.
 
  
Numbers are not NaN or infinity.
 
 
 
 
It's unclear from your question in what format the date should be represented in your JSON. Often, you format dates in some standard date string format (e.g. ISO 8601/RFC 3339 format like 2016-01-25T06:54:00Z). 
 
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.locale = [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"];
formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
formatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ssZZZZZ";
 
Or, for macOS 10.12 and iOS 10, you can do:
 
NSISO8601DateFormatter *formatter = [[NSISO8601DateFormatter alloc] init];
 
Then:
 
NSString *birthDateString = [formatter stringFromDate:birthDate];
 
See Apple Technical Q&A 1480 for more information.
 
Or perhaps, because it's a birthday, you only need yyyy-MM-dd.
 
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.locale = [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"];
formatter.dateFormat = @"yyyy-MM-dd";
NSString *birthDateString = [formatter stringFromDate:birthDate];
 
Bottom line, you have to tell us what format your web service is expecting the dates to be formatted, and then we can help you format it accordingly.