如何使用元数据标记的Retrive函数 [英] How retrive function that marks with metadata

问题描述

查看以下代码段。

  import dart：mirrors; 
 
 class meta {
 final String data; 
 
 const meta（this.data）; 
} 
 
 
 @meta（Tag）
 doSomething（）=> print（你必须做某事）; 
 
 void main（）{
 doSomething（）; 
} 
  

如何检索功能，即市场带有元数据标签？在我的例子中，我想知道，哪个方法标有元标签。

解决方案

  void main（）{
 doSomething ）; 
 getMetaData（）; 
} 
 
 void getMetaData（）{
 LibraryMirror currentLib = currentMirrorSystem（）。libraries.values.last; 
 currentLib.declarations.forEach {
 if（mirror.metadata.length> 0）{
 print（'Symbol $ s has MetaData：$ { mirror.metadata.first.reflectee.data}'）; 
} 
}）; 
} 
  

这应该给你：

符号符号（doSomething）有MetaData：Tag

您还可以从另一个项目分析文件，并在该文件上使用dart：mirrors，而不是检查当前库。可能 libraries.values.last 不会总是返回当前库 - 因此您可能需要更改它。在我的情况下，它工作。

Look at the following code snippet.

import "dart:mirrors";

class meta {
    final String data;

    const meta(this.data);
}


@meta("Tag")
doSomething() => print("You have to do something");

void main() {
    doSomething();
}

How can I retrieve functions, that is market with metadata tags? In my example, I want to find out, which method is marked with meta tags.

解决方案

you could do something like this:

void main() {
    doSomething();
    getMetaData();
}

void getMetaData() {
  LibraryMirror currentLib = currentMirrorSystem().libraries.values.last;
  currentLib.declarations.forEach((Symbol s, DeclarationMirror mirror) {
    if(mirror.metadata.length > 0) {
      print('Symbol $s has MetaData: "${mirror.metadata.first.reflectee.data}"');
    }
  });
}

This should give you:

You have to do something
Symbol Symbol("doSomething") has MetaData: "Tag"

You could also analyze your files from another project and use dart:mirrors on that file instead of inspecting the current library. Maybe libraries.values.last will not always return the current library - so you might need to change it. In my case it worked.

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