nested save

adapters.application.js

import { Promise, defer } from 'rsvp';
import { get } from '@ember/object';

// a mock API response used below
const MOCK_PAYLOAD = {
  person: {
    id: '1',
    name: 'Chris',
    age: 33,
    father: {
      id: '2',
      name: 'Tom',
      age: 65
    },
    friends: [
      { id: '3', name: 'Rebecca', age: 32 },
      { id: '4', name: 'Wesley', age: 35 },
    ]
  }
}

// the guts of the operation
// note that for this to work the transaction needs
// to be coupled to the response format the API will
// utilize in how it builds its `path` for locating
// the id later.
class Transaction {
  records = new Map();
  deferred = defer();

  get promise() {
    return deferred.promise;
  }

  constructor(snapshot) {
    this.records.set(snapshot.record, true);
    this.recursivelySave(snapshot, snapshot.modelName);
  }

  async resolve(payload) {
    let completed = [];
    this.records.forEach((promises, record) => {
      if (promises === true) { return }
      const { path, type } = promises;
      let data = get(payload, path);
      
      // we locationally (by path) map the id within the response
      // back to the original record. By making sure the original
      // record is assigned this ID when the primary payload is
      // processed we don't end up with duplicates or records in an
      // unsaved state.
      promises.resolver.resolve({ data: {
        type,
        id: `${data.id}`
      } });
      completed.push(promises.final);
    });
    
    await Promise.all(completed);
    
    // add another delay for effect
    await new Promise(resolve => setTimeout(resolve, 1500));
    
    return payload;
  }

  recursivelySave(snapshot, path = '<missing>') {
    snapshot.eachRelationship((name, meta) => {
      let related = snapshot[meta.kind](name);
      if (related) {
        if (Array.isArray(related)) {
          related.forEach((r, index) => this.add(r,  path + '.' + name + '.' + index));
        } else {
          this.add(related, path + '.' + name);
        }
      }
    });
  }
  add(snapshot, path = '') {
    // ignore this record if we're already saving it as part of the transaction
    let record = snapshot.record;

    if (this.records.has(record)) {
      return false;
    }
    // initiate a save on the record
    let resolver = defer();
    let save =  record.save({ adapterOptions: { transaction: this } });
    let promises = { save, resolver, path };
    
    this.records.set(record, promises);
    this.recursivelySave(snapshot, path);
   
    return promises;
  }

  get(record) {
  	return this.records.get(record);
  }
}

export default class AppAdapter {
  static create() {
    return new this();
  }

  createRecord() {
    return this.saveRecordAndChildren(...arguments);
  }
  
  // in a real app the difference here may be a POST vs PUT or PATCH
  // but we don't care so we're just going to send create and update
  // through the same save path.
  updateRecord() {
    return this.saveRecordAndChildren(...arguments);
  }
  
  // you could cascade deletes this way too
  deleteRecord() {}
  
  async saveRecordAndChildren(store, ModelClass, snapshot) {
    let transaction = snapshot.adapterOptions?.transaction;

    if (!transaction) {
      // we are the primary (originating) save call
      transaction = new Transaction(snapshot);
    } else {
      // we are one of the nested saves
      let promises = transaction.get(snapshot.record);
      return promises.resolver.promise;
    }
    
    // simulate getting back a payload after some time spent
    // on network
    await new Promise(resolve => setTimeout(resolve, 1500));
    
    return transaction.resolve(MOCK_PAYLOAD);
  }
}

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  init() {
    this._super(...arguments);
    let store = this.get('store');
    let user = store.createRecord('person', { name: 'Chris' });
    let father = store.createRecord('person', { name: 'Tom' });
    let friend1 = store.createRecord('person', { name: 'Rebecca' });
    let friend2 = store.createRecord('person', { name: 'Wesley' });
    
    let friends = user.friends;
    friends.addObject(friend1);
    friends.addObject(friend2);
    
    user.father = father;
 
    this.user = user;
    
    // note if we only wanted to save specific related records
    // and not all related records we could pass adapterOptions
    // into this save with a list of which related props the transaction should include
    // the transaction class here would need to be updated to then include only those vs the current recursive strategy
    // the setTimeout here is just to add some delay so we
    // can observe the states change
    new Promise(resolve => setTimeout(resolve, 1500))
      .then(() => user.save());
  }
});

models.person.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
  name: attr(),
  age: attr(),
  father: belongsTo('person', {
    async: false,
    inverse: null }),
  friends: hasMany('person', {
    async: false,
    inverse: 'friends'
  })
});

serializers.application.js

export default class MySerializer {
  static create() {
    return new this();
  }
  
  normalizeResponse(_, __, rawData) {
    if (rawData.data) {
      return rawData;
    }
    const data = normalizePerson(rawData.person);
    const included = [];
    
    if (rawData.person.father) {
      included.push(normalizePerson(rawData.person.father));
    }
    if (rawData.person.friends) {
      rawData.person.friends.forEach(f => {
        included.push(normalizePerson(f));
      });
    }
    
    return { data, included };
  }
}

function normalizePerson(person) {
  const data = {
      type: 'person',
      id: `${person.id}`,
      attributes: {
        name: person.name,
        age: person.age
      },
      relationships: {}
    };
  if (person.friends) {
    data.relationships.friends = {
      data: person.friends.map(r => { return { type: 'person', id: `${r.id}` }; })
    };
  }
  if (person.father) {
    data.relationships.father = { data: { type: 'person', id: `${person.father.id}` } }
  }
  
  return data;
}

templates.application.hbs

<h1>Saving Related Records (Transactional Saves)</h1>

My user's name is <b>{{this.user.name}}</b> age is <b>{{if this.user.age this.user.age 'unknown'}}</b> and ID is <b>{{if this.user.id this.user.id 'NULL'}}</b>

<br>Their state is: <b>{{this.user.currentState.stateName}}</b>
<hr>
<br>
<b>{{this.user.father.name}}</b> is their father. His age is <b>{{if this.user.father.age this.user.father.age 'unknown'}}</b> and ID is <b>{{if this.user.father.id this.user.father.id 'NULL'}}</b>

<br>His state is: <b>{{this.user.father.currentState.stateName}}</b>
<hr>

<br>
Their friends are:
<ul>
{{#each this.user.friends as |friend|}}
  <li>
    <b>{{friend.name}}</b> whose age is <b>{{if friend.age friend.age 'unknown'}}</b> and ID is <b>{{if friend.id friend.id 'NULL'}}</b>
    <br>Their state is <b>{{friend.currentState.stateName}}</b>
    <br><br>
  </li>
{{/each}}
</ul>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}