Dart: Create method from string

Question

I've been trying to create methods dynamically from strings using Dart to no avail. String example: "(String str) => return str.length;". The idea is to allow users to create their own functions to apply to a given string. The only thing I've found is NoSuchMethod which does not seem to apply to my case. I tried using new Function in JavaScript but when passing the function to Dart and executing it, I get the following error: Uncaught TypeError: J.$index$asx(...).call$0 is not a function.

Code examples:

Dart:

// PHP code
    $files = scandir('stathtml/');
        foreach ($files as $file) {
            $arr1 = substr($files, -5);
            $arr1 = substr($arr1, 4);
            $arr2 = substr($files, 3);
            echo $file . "<br>";
            echo "section ".$arr1 . "<br>";
            echo "chapter".$arr2 . "<br>";
        }

JS:

context["UpdateNames"] =

(JsObject pTag)
{
    print(pTag["function"]("text"));
};

EDIT:

Solution: Create an object in JavaScript such as this:

function execute ()
{
    var func = {"function": new Function("str", "return str.length;")};
    UpdateNames(func);
}

Then create the object in Dart:

this.fun = function (name)
  {
    var text = "var funs = " + document.getElementById("personalFun").value;
    eval(text);
    return funs(name);
  };

Finally call the method to dynamically create the function:

caller = new JsObject(context['Point'], []);

Answer 1

我不确定完全理解你想要达到的目标，所以我会努力提供最好的答案

您希望将方法动态添加到具有特定字符串标识符

的类中

在这种情况下，它完全可以，但你需要使用一些镜像所以要小心，如果你想将它用于网络

这是一个实现示例：

import "dart:mirrors";

class Test {
  Map<String, dynamic> _methods = {};

  void addMethod(String name, var cb) {
    _methods[name] = cb;
  }

  void noSuchMethod(Invocation inv) {
    if (inv.isMethod) {
      Function.apply(_methods[MirrorSystem.getName(inv.memberName)],     inv.positionalArguments);
    }
  }
}

void testFunction() {
  for (int i = 0; i < 5; i++) {
    print('hello ${i + 1}');
  }
}

void testFunctionWithParam(var n) {
  for (int i = 0; i < 5; i++) {
    print('hello ${i + n}');
  }
}

void main() {
  var t = new Test();

  t.addMethod("printHello", testFunction);
  t.addMethod("printHelloPlusN", testFunctionWithParam);
  t.printHello();
  t.printHelloPlusN(42);
}

你想＆＃34;执行＆＃34;字符串中的代码

抱歉，但不可能。它是一个很受欢迎的功能，但它不是由飞镖团队计划的，因为它将涉及许多变化和传播。

也许可以通过创建dart文件并使用isolate进行操作来制作它。

Answer 2

解决方案：使用JavaScript创建一个对象：

var FunctionObject = function() {
  this.fun = function (name)
  {
    var text = "var funs = " + document.getElementById("personalFun").value;
    eval(text);
    return funs(name);
  };
};

然后在Dart中创建对象：

caller = new JsObject(context['FunctionObject'], []);

最后调用方法动态创建函数：

caller.callMethod('fun', [text]);