Dart - class exists from string - class instance from string

Question

I was wondering if it is possible to find out whether a class (in the same library) exists by name (String) and also if it is possible to create an instance of a class from a name (String).

In PHP you can do it like:

$className = 'SomeClass';
if (class_exists($className))
    $instance = new $className;

See also stackoverflow.com/questions/14242712/…

Günter Zöchbauer
– Günter Zöchbauer

2016-03-09 20:12:47 +00:00
Commented Mar 9, 2016 at 20:12 — Günter Zöchbauer
– Günter Zöchbauer, Commented Mar 9, 2016 at 20:12

Günter Zöchbauer · Accepted Answer · 2015-11-10 13:14:15Z

1

I would do it more like

import 'dart:mirrors';

class SomeClass {}

main() {
  String className = 'SomeClass';
  var instance;

  ClassMirror cm = currentMirrorSystem().isolate.rootLibrary.declarations[
      new Symbol(className)];
  if (cm != null) {
    instance = cm.newInstance(new Symbol(''), []).reflectee;
  }
  print(instance);
}

answered Nov 10, 2015 at 13:14

Günter Zöchbauer

661k235 gold badges2.1k silver badges1.6k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Kaspi · Accepted Answer · 2015-11-10 12:47:34Z

0

In time of posting this answer, the solution is not as straightforward as in PHP, but it can be managed this way:

String className = 'SomeClass';
if (currentMirrorSystem().isolate.rootLibrary.declarations.keys.join('').contains('Symbol("${className}")'))
    var instance = currentMirrorSystem().isolate.rootLibrary.declarations[new Symbol(className)].newInstance(new Symbol(''), []).reflectee;

It's a little bit naughty approach with searching in a string, but it's the simplest way I could make it working by myself.

Next you can call the instance's properties simply:

instance.method();

Hope it helps someone.

answered Nov 10, 2015 at 12:47

Kaspi

3,7186 gold badges27 silver badges30 bronze badges

1 Comment

Kaspi Over a year ago

My code inspector also keeps warning me: "The method 'newInstance' is not defined for the class 'DeclarationMirror'", but the code works as expected anyway.

Collectives™ on Stack Overflow

Dart - class exists from string - class instance from string

2 Answers 2

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related