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What's the best way to get primitive properties from child/parent?

See original GitHub issue

It seems like anything you want to pass over the postmessage, you just put in methods. But what if you want to pass over static properties, like 'max': 5000. Obviously you could use a getter-ish method and slap it in methods, but I’m wondering if that’s really the best way, or if there could be some way to access properties immediately from the connection.promise’s resonse? eg

connection.promise.then(child =>  console.log(child.max));

Issue Analytics

  • State:closed
  • Created 6 years ago
  • Comments:12 (6 by maintainers)

github_iconTop GitHub Comments

Aaroniuscommented, Apr 18, 2017

You have to go through methods like you’re talking about. So in your child iframe you might have something like this:

const childModel = {
  max: 5000

const connection = Penpal.connectToParent({
  methods: {
    get(name) {
      return childModel[name];

And then from the parent:

connection.promise.then(child => child.get('max').then(max => console.log(max)));
loganvolkerscommented, May 5, 2017

I like the configuration use case, such as using debug to tell a child to operate in debug mode.

IMHO the most common mistake with @gajewsk2’s proposal would be someone expects Penpal to create a proxy object instead of freezing the property.

var object = {};
object.debug: true;
object.getDebug: function(){ return object.debug; };


object.debug = false;

// Later
child.getDebug().then(debug => debug === child.debug) // Why aren't they equal?

child.debug.get().then(...) // OR! should we provide async getters for props so that mutations can go through

A couple suggestions here:

  • Separate methods from metadata e.g Penpal.connectToParent(methods,metadata). Would help clarify the difference between the static frozen properties and the dynamic methods. Access via parent._metadata.debug.
  • Use Object.freeze to freeze the properties.

** Aside **

For Parent->Child communication the fastest approach wouldn’t used PostMessage at all, it would use query params or hash params. That way if you were trying to get the Client to debug, it would happen immediately instead of only after the handshake is complete. I’m not suggesting we do this, just reminding about speediness of passing configuration details.

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