data-structure.md

Data Structure

There's an opinionated default on how this addon will structure your Cloud Firestore data. More of it will be explained below but basically:

• Documents are stored under a collection derived from their camelized and pluralized model name (e.g. user = users, city = cities, and blog-post = blogPosts)
• Attributes are camelized
• Relationships are stored as Reference data type instead of their IDs
• One-to-many relationships are only persisted in the belongsTo side.

There are however, APIs that would allow the adapter to consume whatever data structure that you already have.

Example Data

Below demonstrates some simple Ember Data models and how they'd look like when persisted in Cloud Firestore.

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

export default class GroupModel extends Model {
  @attr title;
  @hasMany('post') posts;
  @hasMany('user') members;
}

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

export default class PostModel extends Model {
  @attr title;
  @attr body;
  @attr('timestamp') createdOn;
  @belongsTo('user') author;
  @belongsTo('group') group;
}

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

export default class UserModel extends Model {
  @attr name;
  @hasMany('group') groups;
  @hasMany('post') posts;
}

Persisted Structure

{
  "groups": {  // Root-level collection
    "group_a": {
      "name": "Group A",

      "members": {  // Subcollection
        "user_a": {
          "referenceTo": "<reference to users/user_a>"
        }
      }
    }
  },

  "posts": { // Root-level collection
    "post_a": {
      "title": "Post A Title",
      "body": "Post A Body",
      "createdOn": "January 1, 2017 at 12:00:00 AM UTC+8",
      "author": "<reference to users/user_a>",
      "group": "<reference to groups/group_a>"
    }
  },

  "users": {  // Root-level collection
    "user_a": {
      "name": "User A",

      "groups": {  // Subcollection
        "group_a": {
          "referenceTo": "<reference to groups/group_a>"
        }
      }
    }
  }
}

Notes:

• Notice that we don't have a posts subcollection in groups/group_a and users/user_a. This is because in one-to-many relationships, only the belongsTo side gets persisted.
• Relationships are saved as Reference data type instead of its ID of type string.
• referenceTo is a reserved attribute to indicate that a field is a reference to another document. You can configure this to be named as something else. This works as follows:
  • When you fetch a Group document under users/user_a/groups/group_a and it has a referenceTo field to groups/group_a, it will return the document under that instead.
  • If the referenceTo field doesn't exist, it would return the users/user_a/groups/group_a as the document for the Group model.

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