loopback-example-relations

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

In this example, we create a simple web app to demonstrate basic 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.

Prerequisites

Tutorials

• Getting started with LoopBack
• Tutorial series - Step 1

Knowledge

• LoopBack boot scripts
• LoopBack models
• Loopback model relations

Procedure

Create the application

Application information

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

$ slc loopback loopback-example-model-relations
... # follow the prompts
$ cd loopback-example-model-relations

Create the models

Model information

• Name: Customer
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: Yes
  • Custom plural form: Leave blank
  • Properties:
    • name
      • String
      • Not Required
    • age
      • String
      • Not Required
• Name: Review
  • Data source: db (memory)
  • Base class: PersistedModel
  • Expose over REST: Yes
  • Custom plural form: Leave blank
  • Properties:
    • product
      • String
      • Not Required
    • star
      • 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
    • total
      • Number
      • Not Required

$ slc loopback:model Customer
... # follow the prompts, repeat for `Review` and `Order` models

Configure server-side views

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

Add server-side templating configurations to server.js.

Create index.ejs in the views directory.

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

Add sample data

Create three boot scripts:

• sample-customers.js
• sample-orders.js
• sample-reviews.js

Create model relations

Model relation information

• Customer
  • has many
    • Review
      • Property name for the relation: reviews
      • Custom foreign key: authorId
    • Order
      • Property name for the relation: orders
      • Custom foreign key: customerId
      • Require a through model: No
• Review
  • belongs to
    • Customer
      • Property name for the relation: author
      • Custom foreign key: authorId
• Order
  • belongs to
    • Customer
      • Property name for the relation: Leave blank - defaults to customer
      • Custom foreign key: Leave blank

$ slc loopback:relation
? Select the model to create the relationship from:
...
> Customer
... # follow the prompts, repeat for `Review` and `Order`

LoopBack automatically derives relation and foreign key names when you leave the values empty.

Try the API

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

• /api/customers
  • List all customers
• /api/customers?filter[fields][0]=name
  • List all customers, but only return the name property for each result
• /api/customers/1
  • Look up a customer by ID
• /api/customers/youngFolks
  • List a predefined scope named youngFolks
• /api/customers/1/reviews
  • List all reviews posted by a given customer
• /api/customers/1/orders
  • List all orders placed by a given customer
• /api/customers?filter[include]=reviews
  • List all customers including their reviews
• /api/customers?filter[include][reviews]=author
  • List all customers including their reviews which also include the author
• /api/customers?filter[include][reviews]=author&filter[where][age]=21
  • List all customers whose age is 21, including their reviews which also include the author
• /api/customers?filter[include][reviews]=author&filter[limit]=2
  • List first two customers including their reviews which also include the author
• /api/customers?filter[include]=reviews&filter[include]=orders
  • List all customers including their reviews and orders

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