Skip to content

Latest commit

 

History

History
223 lines (180 loc) · 4.19 KB

loopback04.md

File metadata and controls

223 lines (180 loc) · 4.19 KB
Raw

Lets explore with loopback to learn how to link models.

Lets create one more model

Product Model

  • name
  • brand
  • price
  • discount

Once created this is how the model file look like. product.json

{
  "name": "Product",
  "base": "PersistedModel",
  "idInjection": true,
  "options": {
    "validateUpsert": true
  },
  "properties": {
    "name": {
      "type": "string",
      "required": true
    },
    "brand": {
      "type": "string",
      "required": true
    },
    "price": {
      "type": "number",
      "required": true
    },
    "discount": {
      "type": "number"
    }
  },
  "validations": [],
  "relations": {},
  "acls": [],
  "methods": {}
}

product.json

'use strict';

module.exports = function(Product) {

};

Lets add relationship to both models

So we have two models. (tables)

Now we need to link them. Here is how the relationship look like.

Category 1...* Product

1..* means (one to many)

  • One Category has many Products
  • Product belongs a category

Lets see how to do this.

  • One Category has many Products
root@3da899db6882:/usr/src/app/backend# lb relation 
? Select the model to create the relationship from: Category
? Relation type: has many
? Choose a model to create a relationship with: Product
? Enter the property name for the relation: products
? Optionally enter a custom foreign key: 
? Require a through model? No
? Allow the relation to be nested in REST APIs: No
? Disable the relation from being included: No
  • Product belongs a category
root@3da899db6882:/usr/src/app/backend# lb relation
? Select the model to create the relationship from: Product
? Relation type: belongs to
? Choose a model to create a relationship with: Category
? Enter the property name for the relation: category
? Optionally enter a custom foreign key: 
? Allow the relation to be nested in REST APIs: No
? Disable the relation from being included: No

How to verify the your model's relationship

Look at the respective model*.json files

  1. category.json
{
  "name": "Category",
  "base": "PersistedModel",
  "idInjection": true,
  "options": {
    "validateUpsert": true
  },
  "properties": {
    "name": {
      "type": "string",
      "required": true
    }
  },
  "validations": [],
  "relations": {
    "products": {
      "type": "hasMany",
      "model": "Product",
      "foreignKey": ""
    }
  },
  "acls": [],
  "methods": {}
}
  1. product.json
{
  "name": "Product",
  "base": "PersistedModel",
  "idInjection": true,
  "options": {
    "validateUpsert": true
  },
  "properties": {
    "name": {
      "type": "string",
      "required": true
    },
    "brand": {
      "type": "string",
      "required": true
    },
    "price": {
      "type": "number",
      "required": true
    },
    "discount": {
      "type": "number"
    }
  },
  "validations": [],
  "relations": {
    "category": {
      "type": "belongsTo",
      "model": "Category",
      "foreignKey": ""
    }
  },
  "acls": [],
  "methods": {}
}

FYI - You can see that the relation is updates with appropriate values.

NOW its time to test it again.

Let's run the api server again.

root@3da899db6882:/usr/src/app/backend# node .
Web server listening at: http://localhost:3000
Browse your REST API at http://localhost:3000/explorer

Hint: By now , you should know in which folder that you can run this command.

Open the browser, you should be able see some extra API's for both models with foreign-key. Thats prety cool right?.

Exercise 1:

Test the relationship, by creating few products with a category id.

Exercise:

{
  "name": "Addidas men's alpha original",
  "brand": "Addidas",
  "price": 300,
  "discount": 10,
  "categoryId": 1
}

Exercise 2:

Oops. We forget to add an important property to our model.

  • imageurl of the product.

Now , Try to add it.

TIPS: use lb property

Exercise 3:

Prepare your data for the Angular APP

  • Create two categories
  • Create 3 products under each category.

Hint: You can go to Lazada, amazon. to get some actucal products and image urls.

Explore again and learn from it: API Explorer

click here for next stage