Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
1.4k views
in Technique[技术] by (71.8m points)

dart - Instantiate a class from a string

In dart is it possible to instantiate a class from a string?

For example:

  • vanilla in javascript:
var myObject = window[classNameString];
  • Objective-C:
id myclass = [[NSClassFromString(@"MyClass") alloc] init];
See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

You need to know the library name and class name to make things work properly. Assume you know both, the below example will instantiate the TestClass and call doStuff on it.

library test;

import "dart:mirrors";

class TestClass {
  doStuff() => print("doStuff was called!");
}

main() {
  MirrorSystem mirrors = currentMirrorSystem();
  LibraryMirror lm = mirrors.libraries['test'];
  ClassMirror cm = lm.classes['TestClass'];
  Future tcFuture = cm.newInstance('', []);
  tcFuture.then((InstanceMirror im) {
    var tc = im.reflectee;
    tc.doStuff();
  });
}

A few notes about this solution:

  1. The library test we are trying to load the class from is already imported in the VM, which makes this case a bit easier.
  2. the call the newInstance allows for passing parameters to the constructor. Positional arguments are implemented, but named parameters are not yet implemented (as of the M2 release).
  3. newInstance returns a Future to allow it to work across isolates.

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...