Client-side: capturing data from "/posts" server-side response?

I have included a field in the server-side response returned when a user creates a new topic. I’d like to update the client-side with this data.

The field is called stripe_txn_balance, and is present in the following response from the POST to /posts:

JSON response
      "action": "create_post",
      "post": {
        "id": 30,
        "name": null,
        "username": "chris",
        "avatar_template": "/letter_avatar_proxy/v2/letter/c/958977/{size}.png",
        "created_at": "2018-03-05T13:09:45.534Z",
        "cooked": "\u003cp\u003easdasdasdasdasdasdasdasdad\u003c/p\u003e",
        "post_number": 1,
        "post_type": 1,
        "updated_at": "2018-03-05T13:09:45.534Z",
        "reply_count": 0,
        "reply_to_post_number": null,
        "quote_count": 0,
        "avg_time": null,
        "incoming_link_count": 0,
        "reads": 0,
        "score": 0,
        "yours": true,
        "topic_id": 24,
        "topic_slug": "dasdasd",
        "display_username": null,
        "primary_group_name": null,
        "primary_group_flair_url": null,
        "primary_group_flair_bg_color": null,
        "primary_group_flair_color": null,
        "version": 1,
        "can_edit": true,
        "can_delete": false,
        "can_recover": null,
        "can_wiki": true,
        "user_title": null,
        "actions_summary": [
            "id": 5,
            "hidden": true,
            "can_act": true
            "id": 3,
            "can_act": true
            "id": 4,
            "can_act": true
            "id": 8,
            "can_act": true
            "id": 7,
            "can_act": true
        "moderator": false,
        "admin": true,
        "staff": true,
        "user_id": 1,
        "draft_sequence": 1,
        "hidden": false,
        "hidden_reason_id": null,
        "trust_level": 4,
        "deleted_at": null,
        "user_deleted": false,
        "edit_reason": null,
        "can_view_edit_history": true,
        "wiki": false,
        "stripe_txn_balance": 0
      "success": true

When I get the response I’ll be doing something like this on the client side:

Discourse.User.current().set("stripe_txn_balance", post.stripe_txn_balance);

What I’d like to know is where’s best to put this code?

I tried doing the following in an initializer but couldn’t find my field in the model:

api.modifyClass('controller:composer', {
    save(force) {
        const promise = this._super(force);
        const model = this;
        if (promise) {
            promise.then(function(value) {

model.topic evaluates to this, but it doesn’t include my field (and I also couldn’t find my field elsewhere within model:

A nudge in the right direction would be much appreciated.

I think message bus is more suitable for your purpose.

Message bus would be good in order to decouple the code.

However, I’m still none the wiser as to how to extract the stripe_txn_balance field from the composer post response from the server?

The JSON response is loaded inside result.responseJson. Try like below

promise.then(result => {

Thanks @vinothkannans for your suggestion.

After much fiddling this is the only approach that worked:

api.modifyClass('model:composer', {
    createPost(opts) {
        const result = this._super(opts);
        if (result) {
            result.then(r => {
                if (r.payload && typeof(r.payload.stripe_txn_balance) !== 'undefined') {
                    Discourse.User.current().set("stripe_txn_balance", r.payload.stripe_txn_balance);
        return result;