[英]Dart Polymer error 'List' is not a subtype of type 'ObservableList' of 'value'
我正在使用core-ajax-dart來獲取一些數據並將其放入core-list-dart中。 而且我不斷收到此錯誤。 我能夠成功傳遞標題為String的標題,但無法傳遞聯系人。 失敗並顯示以下錯誤
異常:未捕獲的錯誤:類型“列表”不是“值”的類型“可觀察的列表”的子類型。
主頁
<core-ajax-dart auto id="_ajax" url="https://polymer-contacts.firebaseio.com/{{category}}.json" handleAs="json"></core-ajax-dart>
<contacts-page class="page" id="contacts" contacts="{{contacts}}" heading="{{heading}}" flex></contacts-page>
List contacts;
ContactsPage cp = $['contacts'] as ContactsPage;
var ajax = $['_ajax'] as CoreAjax;
ajax.on["core-response"].listen((event) {
var detail = event.detail;
var response = detail['response'];
cp.contacts = response;
});
元素定義
<div id="title" flex>{{heading}}</div>
<core-list-dart id="list" data="{{contacts}}">
@published List contacts;
@published String heading;
堆棧跟蹤:
Exception: Uncaught Error: type 'List' is not a subtype of type 'ObservableList' of 'value'.
Stack Trace:
#0 CoreList.data= (package:core_elements/core_list_dart.dart:48:124)
#1 main.<anonymous closure> (http://localhost:8080/index.html_bootstrap.dart:114:27)
#2 GeneratedObjectAccessorService.write (package:smoke/static.dart:114:11)
#3 write (package:smoke/smoke.dart:34:40)
#4 _updateNode (package:polymer/src/instance.dart:1412:16)
#5 _convertAndCheck (package:polymer_expressions/polymer_expressions.dart:302:16)
#6 _RootZone.runUnaryGuarded (dart:async/zone.dart:1093)
#7 _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:341)
#8 _DelayedData.perform (dart:async/stream_impl.dart:595)
#9 _StreamImplEvents.handleNext (dart:async/stream_impl.dart:711)
#10 _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:671)
#11 _asyncRunCallbackLoop (dart:async/schedule_microtask.dart:41)
#12 _asyncRunCallback (dart:async/schedule_microtask.dart:48)
#13 _handleMutation (dart:html:41817)
<core-list-dart>
的data屬性需要一個ObservableList
而不是List
。
您可以做的是將字段更改為getter / setter,將傳遞的List
自動轉換為ObservableList
例如
class Model extends Object with Observable {
// or class SomeElement extends PolymerElement {
ObservableList _contacts;
@observable ObservableList get contacts => _contacts;
set contacts(List contacts) {
final old = _contacts;
if(contacts is ObservableList) {
_contacts = contacts;
}
_contacts = toObservable(contacts);
notifyPropertyChange(#contacts, old, _contacts);
}
}
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