如何检索Dartlang中的元数据? [英] How to retrieve metadata in Dartlang?
问题描述
Dartlang教程介绍程序包:meta
https://www.dartlang.org/docs/dart-up-and-running/contents/ch02.html#ch02-metadata
Dartlang tutorial introduces package:meta https://www.dartlang.org/docs/dart-up-and-running/contents/ch02.html#ch02-metadata
DartEditor识别元数据,如上面的教程所示。本教程还解释了如何创建自定义元数据并检索它。
DartEditor recognise the metadata as shown at above tutorial. The tutorial also explains how to create custom metadata and retrieve it. But there is no code sample on how to retrieve it.
推荐答案
通过阅读一些实现,例如Polymer.dart中的@published元数据,我找到方法。
https://www.dartlang.org/articles/reflection-with- mirrors /
https:/ /api.dartlang.org/apidocs/channels/stable/dartdoc-viewer/dart-mirrors#id_reflect
Through reading some implementations such as @published metadata in Polymer.dart, I find the way. https://www.dartlang.org/articles/reflection-with-mirrors/ https://api.dartlang.org/apidocs/channels/stable/dartdoc-viewer/dart-mirrors#id_reflect
以下是示例代码。
import 'dart:mirrors';
class todo {
final String who;
final String what;
const todo(this.who, this.what);
}
@todo('akira', 'add something')
class Foo {
@todo('naoto', 'do something')
String fooVariable = 'a';
@todo('kitano', 'change the name')
void fooMethod() {
}
}
void main() {
InstanceMirror im = reflect(new Foo());
ClassMirror classMirror = im.type;
// ClassMirror
classMirror.metadata.forEach((metadata) {
print(metadata.reflectee.who); // -> akira
print(metadata.reflectee.what); // -> add something
});
// VariableMirror
for (VariableMirror variable in classMirror.variables.values) {
print(variable.metadata.first.reflectee.who); // -> naoto
print(variable.metadata.first.reflectee.what); // -> do something
}
// MethodMirror
classMirror.methods.values.forEach((MethodMirror method) {
print(method.metadata.first.reflectee.who); // -> kitano
print(method.metadata.first.reflectee.what); // -> change the name
});
}
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