Question

我正在尝试将JSON解析为Dart中的对象，文档使用 Map 类型来解析JSON响应。

关于他们的文件Using Dart with JSON Web Services: Parsing JSON ，我剪了下面的例子：

import 'dart:convert';

main() {
  String mapAsJson = '{"language":"dart"}';  // input Map of data
  Map parsedMap = JSON.decode(mapAsJson);
  print(parsedMap["language"]); // dart
}

我在我的testApp中应用了相同的内容，但它无法正常工作

test() {
  var url = "http://localhost/wptest/wp-json/wp/v2/posts";

  // call the web server asynchronously
  var request = HttpRequest.getString(url).then(onDataLoaded);
}

onDataLoaded(String responseText) {
  Map x = JSON.decode(responseText);
  print(x['title'].toString());
}

我收到此错误

Exception: Uncaught Error: type 'List' is not a subtype of type 'Map' of 'x'.
Stack Trace:
  post.post (package:untitled8/wp/posts.dart:25:24)
  onDataLoaded (http://localhost:63342/untitled8/web/index.dart:24:15)
  _RootZone.runUnary (dart:async/zone.dart:1166)
  _Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:494)
  _Future._propagateToListeners (dart:async/future_impl.dart:577)
  _Future._completeWithValue (dart:async/future_impl.dart:368)
  _Future._asyncComplete.<anonymous closure> (dart:async/future_impl.dart:422)
  _microtaskLoop (dart:async/schedule_microtask.dart:43)
  _microtaskLoopEntry (dart:async/schedule_microtask.dart:52)
  _ScheduleImmediateHelper._handleMutation (dart:html:42567)

Answer 1

文档是正确的。

//if JSON is an array (starts with '[' )

List<Map> x = JSON.decode(responseText);
print(x[0]['title']);

//if JSON is not an array (starts with '{' )

Map z = JSON.decode(responseText);
print(z['content']);
print(z['id']);
print(z['title']);

Answer 2

来自服务器的JSON需要解码为dart中的json，并分配给 String 和 dynamic

类型的映射

json 中的键必须为 String ，而值对的类型必须为 dynamic 来保存任何值，无论是数组，int还是bool

  Map<String,dynamic> z = Map<String,dynamic>.from(JSON.decode(responseText));


    print(z.toString())

在Dart中解析JSON

2 个答案: