从Dart中的JavaScript对象获取任意属性 [英] Getting an arbitrary property from a JavaScript object in Dart

问题描述

编辑：
4：对象是我想要的数据。

解决方案

好，这是一个有趣的节日快乐：）

它看起来像地图 package：js ，不支持code>自动转换。所以有几件事：

1. 提起 https://github.com/dart-lang/sdk/issues/28194


2. 发送了 PR引入了解决方法

对于感兴趣的参与者，我们可以使用浏览器本地的 Object.keys ：

  @JS（）
库示例； 
 
导入 package：js / js.dart； 
 
 ///一种将对象从JS转换为Dart Map的解决方法。 
 Map jsToMap（jsObject）{
返回新Map.fromIterable（
 _getKeysOfObject（jsObject），
值：（key）=> getProperty（jsObject，key），
）; 
} 
 
 //这两个接口都可以从Dart调用Object.keys。 
 // 
 //但是您不能直接使用它们。只需看jsToMap`。 
 @JS（'Object.keys'）
外部列表< String> _getKeysOfObject（jsObject）; 
  

在我们拥有任意JavaScript对象后调用它：

  var属性= jsToMap（toy.getData（））; 
 print（properties）; 
  

Edit: Here is a minimal project that illustrates my issue. You can see the error described by serving it to the browser: pub get and then either pub serve (dartium) or pub build --mode=debug (other browsers).

How can I access an arbitrary JavaScript property from Dart through a JsObjectImpl? I am using the ace.js library with an interop to Dart that I've adapted from a typescript interface, and the method I am calling returns a plain javascript object with key-value pairs.

Dart gives me a JsObjectImpl, which cannot be casted to a Map or a JsObject, both of which have [] accessors. It confusingly seems to inherit from the deprecated JSObject (note the 's' is capitalized in the latter) which does not have the [] accessor, so I can't get the data out.

Some error messages:

1. When attempting a cast from JsObjectImpl to JsObject:
   ORIGINAL EXCEPTION: type 'JSObjectImpl' is not a subtype of type 'JsObject' of 'obj' where JSObjectImpl is from dart:js JsObject is from dart:js. I get a similar message when using Map as well.

2. Looking at the object in the debugger, I can frustratingly see the property in JS view but not in the Dart object:
   
   The 4: Object is the data I want.

解决方案

Ok, this was a fun one, happy holidays :)

It looks like Map is not a supported auto-conversion for package:js. So a couple of things:

1. Filed https://github.com/dart-lang/sdk/issues/28194
2. Sent your a PR introducing a workaround

For interested parties, we can use the browser-native Object.keys:

@JS()
library example;

import 'package:js/js.dart';

/// A workaround to converting an object from JS to a Dart Map.
Map jsToMap(jsObject) {
  return new Map.fromIterable(
    _getKeysOfObject(jsObject),
    value: (key) => getProperty(jsObject, key),
  );
}

// Both of these interfaces exist to call `Object.keys` from Dart.
//
// But you don't use them directly. Just see `jsToMap`.
@JS('Object.keys')
external List<String> _getKeysOfObject(jsObject);

And call it once we have an arbitrary JavaScript object:

var properties = jsToMap(toy.getData());
print(properties);

这篇关于从Dart中的JavaScript对象获取任意属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！