⚠️ This LoopBack 3 example project is no longer maintained. Please refer to LoopBack 4 Examples instead. ⚠️

$ git clone https://github.com/strongloop/loopback-example-relations.git
$ cd loopback-example-relations
$ npm install
$ node .

In this example, we create a simple web app to demonstrate model relation concepts. The app consists of a single web page with a list of links to help us query and filter sample data via REST.

Before starting this tutorial, you must install:

• Node.js
• LoopBack CLI tools; see lb

• Getting started with LoopBack
• Tutorial series - Step 1

• LoopBack boot scripts
• LoopBack models
• Loopback model relations
• Creating loopback model relations

• Name: loopback-example-relations
• Directory to contain the project: loopback-example-relations

$ lb app loopback-example-relations
... # follow the prompts
$ cd loopback-example-relations

• Name: transient
• Connector: other
  • Name: transient

$ lb datasource
... # follow the prompts, choose `other` to define custom connector

• Name: Customer
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: Yes
  • Custom plural form: Leave blank
  • Properties:
    • name
      • String
      • Not Required
    • age
      • number
      • Not Required
• Name: Order
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: Yes
  • Custom plural form: Leave blank
  • Properties:
    • description
      • String
      • Not Required
    • date
      • date
      • Not Required
• Name: Account
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: No
  • Custom plural form: Leave blank
  • Properties:
    • name
      • String
      • Not Required
    • date
      • date
      • Not Required
• Name: Address
  • Data source: transient
  • Base class: Model
  • Expose over REST: No
  • Custom plural form: Leave blank
  • Properties:
    • street
      • String
      • Not Required
    • city
      • String
      • Not Required
    • state
      • String
      • Not Required
    • zipCode
      • String
      • Not Required
• Name: Author
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: No
  • Custom plural form: Leave blank
  • Properties:
    • name
      • String
      • Not Required
• Name: Book
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: Yes
  • Custom plural form: Leave blank
  • Properties:
    • name
      • String
      • Not Required
• Name: EmailAddress
  • Data source: transient
  • Base class: PersistedModel
  • Expose over REST: No
  • Custom plural form: Leave blank
  • Properties:
    • label
      • String
      • Not Required
    • address
      • String
      • Not Required
• Name: Link
  • Data source: transient
  • Base class: Model
  • Expose over REST: No
  • Custom plural form: Leave blank
  • Properties:
    • id
      • number
      • Required

      Please set "id": true manually for this property, like link.json

    • name
      • String
      • Not Required
    • notes
      • String
      • Not Required
• Name: Reader
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: No
  • Custom plural form: Leave blank
  • Properties:
    • name
      • String
      • Not Required
• Name: Shipment
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: No
  • Custom plural form: Leave blank
  • Properties:
    • date
      • Date
      • Not Required
    • description
      • String
      • Not Required

$ lb model Customer
... # follow the prompts, repeat for other models

Upper-case in model's name would be interpreted as '-' in model's file name, eg: EmailAddress has email-address.json

LoopBack comes preconfigured with EJS out-of-box. This means we can use server-side templating by simply setting the proper view engine and a directory to store the views.

Create a views directory to store server-side templates.

$ mkdir server/views

Create index.ejs in the views directory. Create account.ejs in the views directory. Create email.ejs in the views directory. Create address.ejs in the views directory.

Configure server.js to use server-side templating. Remember to import the path package.

Replace the default root.js with a new one which passes a given customer's id to template engine.

Create six boot scripts:

• sample-customers.js
• z-book-people.js
• z-customer-accounts.js
• z-customer-address.js
• z-customer-emails.js

We add z- in front of the boot script names to make sure they load last since LoopBack boot loads boot scripts alphabetically.

• Customer

  • has many

    • Order

      • Property name for the relation: orders
      • Custom foreign key: customerId
      • Require a through model: No

    • Other Relations: (please add them manually)

      "address": {
        "type": "embedsOne",
        "model": "Address",
        "property": "billingAddress",
        "options": {
          "validate": true,
          "forceId": false
        }
      },
      "emails": {
        "type": "embedsMany",
        "model": "EmailAddress",
        "property": "emailList",
        "options": {
          "validate": true,
          "forceId": false
        }
      },
      "accounts": {
        "type": "referencesMany",
        "model": "Account",
        "property": "accountIds",
        "options": {
          "validate": true,
          "forceId": false
        }
      },
      

• Book(please add them manually)

  "people": {
      "type": "embedsMany",
      "model": "Link",
      "scope": {
        "include": "linked"
      }
  }
  

• Link(please add them manually)

  "linked": {
    "type": "belongsTo",
    "polymorphic": {
      "idType": "number"
    },
    "properties": {
      "name": "name"
    },
    "options": {
      "invertProperties": true
    }
  }
  

• Order

  • belongs to
    • Customer
      • Property name for the relation: Leave blank - defaults to customer
      • Custom foreign key: Leave blank
  • has many
    • Shipment
      • Property name for the relation: Leave blank - defaults to shipments
      • Custom foreign key: Leave blank

• Shipment

  • belongs to
    • Order
      • Property name for the relation: Leave blank - defaults to order
      • Custom foreign key: Leave blank

$ lb relation
? Select the model to create the relationship from:
...
> Customer
... # follow the prompts, repeat for other models

Some relations are not available in lb, please add them in model-name.json manually. LoopBack automatically derives relation and foreign key names when you leave the values empty.

Start the application with node . and browse to [localhost:3000][localhost]. You should see various links. Each endpoint is defined as follows:

• /api/customers
  • List all customers
• /api/customers/4
  • Look up a customer by ID
• /api/customers/youngFolks
  • List a predefined scope named youngFolks
• /api/customers/4/orders
  • List a given customer's orders
• /api/customers?filter[include]=orders
  • List all customers including their orders
• /api/customers?filter[include][orders]=customer
  • List all customers including their orders which also include the customer
• /api/customers?filter[include][orders]=customer&filter[where][age]=21
  • List all customers whose age is 21, including their orders
• /api/customers?filter[include][orders]=customer&filter[limit]=2
  • List first two customers including their orders
• /api/customers?filter[include]=accounts&filter[include]=orders
  • List all customers including their accounts and orders

• /api/customers/2/address
  • List a given customer's address

• /api/customers/3/emails
  • List a given customer's email

• api/customers/1/accounts
  • List all accounts owned by a given customer
• /api/customers/1/accounts/1
  • Look up a given accounts of a given customer by foreign key
• /api/customers/1/accounts/count
  • Count accounts number of a given customer

• /api/Books/1/people
  • List the linked people of a given book
• /api/Books/1/people/1
  • Look up the author of a given book by foreign key
• /api/Books/1/people/2
  • Look up the reader of a given book by foreign key

More LoopBack examples