如何在没有关键的情况下解析JSON

问题描述：

我想解析一个JSON.但是此JSON没有键值.只是价值.

I want parse a JSON. But this JSON not have key-value. Is only value.

我尝试创建该类，但是不起作用.错误是列表"类型不是地图"类型的子类型.

I tried creating the class but dont work. The error is type 'List' is not a subtype of type 'Map'.

我试图解析它们在json中所占的位置(例如:json [0]....)但是我对此不确定.

I tried to parse in the positions they occupy in the json (eg.: json [0] ....) But I'm not sure about this.

预先感谢

Json:

[["P170","P171","L-18"],["P171","L806","L-18"],["L806","L807","L-18"],["L807","L120","L-18"],["L120","L121","L-18"],["L121","L122","L-18"]]

班级列表:

import 'NodoPOJO.dart';
class NodoCollection{
  final List<NodoPOJO> list;

  NodoCollection(this.list);

  factory NodoCollection.fromJson(Map<String, dynamic> json) {
    return NodoCollection(
        List.from(json[0]).map((object) =>NodoPOJO.fromJson(object)));
  }


}

POJO类:

class NodoPOJO{
  final String extremo1;
  final String extremo2;
  final String linea;

  NodoPOJO(this.extremo1, this.extremo2, this.linea);


  factory NodoPOJO.fromJson(Map<String, dynamic> json) {
    return NodoPOJO(json[0], json[1],json[2]);
  }

}

答

json.decode()返回dynamic，因为json的每个元素都可以是对象(成为Dart Map)或数组(成为Dart ). json解码直到开始解码才知道返回什么.

json.decode() returns a dynamic because each element of json could be an object (becomes a Dart Map) or array (becomes a Dart List). The json decode doesn't know what it is going to return until it starts decoding.

按如下所示重写您的两个类:

Rewrite your two classes as follows:

class NodoCollection {
  final List<NodoPOJO> list;

  NodoCollection(this.list);

  factory NodoCollection.fromJson(List<dynamic> json) =>
      NodoCollection(json.map((e) => NodoPOJO.fromJson(e)).toList());
}

class NodoPOJO {
  final String extremo1;
  final String extremo2;
  final String linea;

  NodoPOJO(this.extremo1, this.extremo2, this.linea);

  factory NodoPOJO.fromJson(List<dynamic> json) =>
      NodoPOJO(json[0], json[1], json[2]);
}

如何在没有关键的情况下解析JSON

相关推荐