1.应用场景
接口传输数据时,有时需要用POST传一长串string数据,一般要求转为json格式方便服务器解析
2.需要转义的字符说明及oc方法实现
NSString转json时若包含以下字符,需要进行转义
" (双引号)
/ (正斜线)
\n (换行符)
\b (退格符)
\f (换页符)
\r (回车符)
\t (制表符,一个tab或按8下空格)

oc方法如下

• (NSString *)string2JSONString:(NSString *)string {
  NSMutableString *s = [NSMutableString stringWithString:string];
  [s replaceOccurrencesOfString:@""" withString:@"\"" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
  [s replaceOccurrencesOfString:@"/" withString:@"\/" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
  [s replaceOccurrencesOfString:@"\n" withString:@"\n" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
  [s replaceOccurrencesOfString:@"\b" withString:@"\b" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
  [s replaceOccurrencesOfString:@"\f" withString:@"\f" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
  [s replaceOccurrencesOfString:@"\r" withString:@"\r" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
  [s replaceOccurrencesOfString:@"\t" withString:@"\t" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [s length])];
  return [NSString stringWithString:s];
  }
  3.读取文本文件内容POST方法上传,参数放在body内

• (void)uploadJsonStringAsyn{
  //读取txt文件内容(包含回车空格等特殊字符)转为jsonString
  NSMutableDictionary params = [[NSMutableDictionary alloc] init];
  NSString midiPath = [[NSBundle mainBundle] pathForResource:@"test" ofType:@"txt"];
  NSFileHandle readHandle = [NSFileHandle fileHandleForReadingAtPath:midiPath];
  [readHandle seekToFileOffset:0];
  NSData data = [readHandle readDataToEndOfFile];
  NSString *midiStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
  params[@"jsonString"] = [self string2JSONString:midiStr];

  //设置上传地址
  NSString *urlString = [NSString stringWithFormat:@"http://"];
  NSURL *url = [NSURL URLWithString:urlString];
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
  [request setHTTPMethod:@"POST"];
  [request addValue:@"application/json;charset=UTF-8" forHTTPHeaderField:@"Content-Type"];

  NSData *jsonData = [NSJSONSerialization dataWithJSONObject:params options:NSJSONWritingPrettyPrinted error:nil];
  //添加参数
  [request setHTTPBody:jsonData];

  //创建session对象
  NSURLSession *session = [NSURLSession sharedSession];

  //创建一个请求任务
  NSURLSessionTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
  NSString *result = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
  NSLog(@"POST%@",result);
  }];

  [task resume];
  }
  4.iOS字典(NSDictionary)和JSON字符串之间互转
  注意: 若midiStr是字典中键对应值,无需调用string2JSONString:

  NSMutableDictionary params = [[NSMutableDictionary alloc] init];
  NSString midiPath = [[NSBundle mainBundle] pathForResource:@"test11" ofType:@"txt"];
  NSFileHandle readHandle = [NSFileHandle fileHandleForReadingAtPath:midiPath];
  [readHandle seekToFileOffset:0];
  NSData data = [readHandle readDataToEndOfFile];
  NSString *midiStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
  params[@"info"] = midiStr;

  NSString *jsonString = [self convert2JSONWithDictionary:params];
  [self convert2DictionaryWithJSONString:jsonString];
  4-1 字典转JSON

• (NSString *)convert2JSONWithDictionary:(NSDictionary *)dic{
  NSError *err;
  NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dic options:0 error:&err];

  NSString *jsonString;
  if (!jsonData) {
  NSLog(@"%@",err);
  }else{
  jsonString = [[NSString alloc]initWithData:jsonData encoding:NSUTF8StringEncoding];
  }
  NSLog(@"%@",jsonString);
  return jsonString;
  }
  4-2 JSON转字典

• (NSDictionary *)convert2DictionaryWithJSONString:(NSString *)jsonString{
  NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
  NSError *err;
  NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:jsonData
  options:NSJSONReadingMutableContainers
  error:&err];
  if(err)
  {
  NSLog(@"%@",err);
  return nil;
  }
  return dic;
  }

作者：Jesscia_Liu
链接：https://www.jianshu.com/p/2cea35159160
来源：简书
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