如何使用Dart的JS互操作创建匿名JavaScript函数/回调? [英] How do I create an anonymous JavaScript function/callback with Dart's JS interop?
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问题描述
我使用Dart及其 JS互操作 。我需要将以下JavaScript代码转换为Dart:
I am using Dart and its JS interop. I need to convert the following JavaScript code to Dart:
ID3.loadTags("filename.mp3", function() {
var tags = ID3.getAllTags("filename.mp3");
if (tags.artist)
artist.textContent = tags.artist;
if (tags.title)
track.textContent = tags.title;
}, {
dataReader: FileAPIReader(file)
});
请注意匿名回调作为 loadTags的第二个参数
。我如何使用Dart和 dart:js
库创建它?
Note the anonymous callback as the second parameter to loadTags
. How do I create that with Dart and the dart:js
library?
函数:
js.context['loadTagsCallback'] = () {
var tags = ID3.callMethod('getAllTags', ["filename.mp3"]);
var artistTag = tags['artist'];
var titleTag = tags['title'];
if (artistTag != null) {
artist.text = artistTag;
}
if (titleTag != null) {
track.text = titleTag;
}
};
然后使用此Dart代码:
And then using this Dart code:
ID3.callMethod('loadTags', [
"filename.mp3",
js.context['loadTagsCallback'],
new js.JsObject.jsify({'dataReader': id3FileReader})
]);
但是,我不想创建命名函数。任何想法或提示?
However, I don't want to create the named function. Any ideas or tips?
推荐答案
Dart闭包在跨边界发送时会自动转换为JS闭包。您只需这样做:
Dart closures are automatically converted to JS closures when sent across the border. You can just do this:
ID3.callMethod('loadTags', ["filename.mp3", () {
var tags = ID3.callMethod('getAllTags', ["filename.mp3"]);
var artistTag = tags['artist'];
var titleTag = tags['title'];
if (artistTag != null) {
artist.text = artistTag;
}
if (titleTag != null) {
track.text = titleTag;
}
},
new js.JsObject.jsify({'dataReader': id3FileReader})
]);
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