codetombomb / scf-serializers

11-5 Rails Serializers

What is serialization?

ActiveModel::Serializer, or AMS, provides a convention-based approach to serializing resources or shaping our data to fit our needs.

How have we been serializing up to this point?

• In Rails controllers, we have been using render json: and in Sinatra, we used the to_json method and passed any options to customize data or include data associations.

When to use AMS over controller serialization?

• More commonly, we want to include AMS when data structures become complex and require a lot of customization.
• Best practice for separation of concerns tells us we should always use AMS to isolate the responsibility of serialization from the controllers.

How to use AMS

• Add gem to Gemfile:

gem 'active_model_serializers'

• And then run bundle install
• or run:
  • bundle add active_model_serializers
• To generate a new serializer, run serializer generator:

rails g serializer <serializer_name> #use singular naming here

If convention is followed, serializers will match the respective model object.

def show
	render json: category
	# this will invoke upon the CategorySerializer for a single instance
end

To serialize a collection with a custom serializer, the each_serializer method can be used to pass each instance to the serializer:

def index
  categories = Category.all
  render json: categories, each_serializer: CustomSerializer
end

Serializing the Alley Cat app data

Alley Cat Antiques ERD

Category

• Serialize with a name
• Serialize with a list of items including:
  • name, desc, price in 2 decimal format, with a dollar sign at the beginning i.e. $10.50
  • Define a method #status that will return 'sold' if self.sold returns true and 'Buy Now' if false.
  • Return the items seller with username and email included.

[
  {
    "id": 1,
    "name": "fishing",
    "items": [
      {
        "id": 1,
        "name": "fishing pole",
        "desc": "really cool fishing pole!",
        "price": "$10.00",
        "status": "Buy Now"
      }
    ]
  },
  {
    "id": 2,
    "name": "camping",
    "items": [
      {
        "id": 1,
        "name": "fishing pole",
        "desc": "really cool fishing pole!",
        "price": "$10.00",
        "status": "Buy Now"
      }
    ]
  },
  {
    "id": 3,
    "name": "womens clothing",
    "items": [
      {
        "id": 2,
        "name": "white t",
        "desc": "get hip with this cool shirt",
        "price": "$5.00",
        "status": "Buy Now"
      }
    ]
  },
  {
    "id": 4,
    "name": "mens clothing",
    "items": [
      {
        "id": 2,
        "name": "white t",
        "desc": "get hip with this cool shirt",
        "price": "$5.00",
        "status": "Buy Now"
      }
    ]
  },
  {
    "id": 5,
    "name": "electronics",
    "items": [
      {
        "id": 5,
        "name": "vintage walkman",
        "desc": "go back in time with this music player",
        "price": "$5.25",
        "status": "Buy Now"
      }
    ]
  },
  {
    "id": 6,
    "name": "decor",
    "items": [
      {
        "id": 3,
        "name": "gold round mirror",
        "desc": "vintage mirror",
        "price": "$30.50",
        "status": "Buy Now"
      },
      {
        "id": 4,
        "name": "marble table lamp",
        "desc": "really cool marble lamp",
        "price": "$27.50",
        "status": "Buy Now"
      }
    ]
  },
  {
    "id": 7,
    "name": "home",
    "items": [
      {
        "id": 3,
        "name": "gold round mirror",
        "desc": "vintage mirror",
        "price": "$30.50",
        "status": "Buy Now"
      },
      {
        "id": 4,
        "name": "marble table lamp",
        "desc": "really cool marble lamp",
        "price": "$27.50",
        "status": "Buy Now"
      }
    ]
  },
  {
    "id": 8,
    "name": "living room",
    "items": [
      {
        "id": 3,
        "name": "gold round mirror",
        "desc": "vintage mirror",
        "price": "$30.50",
        "status": "Buy Now"
      },
      {
        "id": 4,
        "name": "marble table lamp",
        "desc": "really cool marble lamp",
        "price": "$27.50",
        "status": "Buy Now"
      }
    ]
  }
]

---

Item

• Serialize with: name, desc, price
• price should be in a 2 decimal format, with a dollar sign at the beginning i.e. $10.50
• Define a method #status that will return 'sold' if self.sold returns true and 'buy now' if false
• Return the items seller with username and email included.
• Each item should also return a list of associated categories including the name

[
  {
    "id": 1,
    "name": "fishing pole",
    "desc": "really cool fishing pole!",
    "price": "$10.00",
    "status": "Buy Now",
    "seller": {
      "id": 1,
      "username": "codetombomb",
      "email": "[email protected]"
    },
    "categories": [
      {
        "id": 1,
        "name": "fishing"
      },
      {
        "id": 2,
        "name": "camping"
      }
    ]
  },
  {
    "id": 2,
    "name": "white t",
    "desc": "get hip with this cool shirt",
    "price": "$5.00",
    "status": "Buy Now",
    "seller": {
      "id": 1,
      "username": "codetombomb",
      "email": "[email protected]"
    },
    "categories": [
      {
        "id": 3,
        "name": "womens clothing"
      },
      {
        "id": 4,
        "name": "mens clothing"
      }
    ]
  },
  {
    "id": 3,
    "name": "gold round mirror",
    "desc": "vintage mirror",
    "price": "$30.50",
    "status": "Buy Now",
    "seller": {
      "id": 2,
      "username": "eriiscool",
      "email": "[email protected]"
    },
    "categories": [
      {
        "id": 6,
        "name": "decor"
      },
      {
        "id": 7,
        "name": "home"
      },
      {
        "id": 8,
        "name": "living room"
      }
    ]
  },
  {
    "id": 4,
    "name": "marble table lamp",
    "desc": "really cool marble lamp",
    "price": "$27.50",
    "status": "Buy Now",
    "seller": {
      "id": 2,
      "username": "eriiscool",
      "email": "[email protected]"
    },
    "categories": [
      {
        "id": 6,
        "name": "decor"
      },
      {
        "id": 8,
        "name": "living room"
      },
      {
        "id": 7,
        "name": "home"
      }
    ]
  },
  {
    "id": 5,
    "name": "vintage walkman",
    "desc": "go back in time with this music player",
    "price": "$5.25",
    "status": "Buy Now",
    "seller": {
      "id": 2,
      "username": "eriiscool",
      "email": "[email protected]"
    },
    "categories": [
      {
        "id": 5,
        "name": "electronics"
      }
    ]
  }
]

---

User

Reminder that user can behave as either a seller and/or buyer. When a request to the users index or show is made, serialized data should return all items that have been purchased and/or sold.

• Serialize with username and email
• Return a list of both sold_items and purchased_items. These lists should be returned as separate collections.
• Return a list of the categories as sold_categories and purchased_categories, with only the category name included.

[
  {
    "id": 1,
    "username": "codetombomb",
    "email": "[email protected]",
    "purchased_items": [
      {
        "id": 5,
        "name": "vintage walkman",
        "desc": "go back in time with this music player",
        "price": "$5.25",
        "status": "Buy Now"
      }
    ],
    "sold_items": [
      {
        "id": 1,
        "name": "fishing pole",
        "desc": "really cool fishing pole!",
        "price": "$10.00",
        "status": "Buy Now"
      },
      {
        "id": 2,
        "name": "white t",
        "desc": "get hip with this cool shirt",
        "price": "$5.00",
        "status": "Buy Now"
      }
    ],
    "sold_categories": [
      {
        "id": 1,
        "name": "fishing"
      },
      {
        "id": 2,
        "name": "camping"
      },
      {
        "id": 3,
        "name": "womens clothing"
      },
      {
        "id": 4,
        "name": "mens clothing"
      }
    ],
    "purchased_categories": [
      {
        "id": 5,
        "name": "electronics"
      }
    ]
  },
  {
    "id": 2,
    "username": "eriiscool",
    "email": "[email protected]",
    "purchased_items": [
      
    ],
    "sold_items": [
      {
        "id": 3,
        "name": "gold round mirror",
        "desc": "vintage mirror",
        "price": "$30.50",
        "status": "Buy Now"
      },
      {
        "id": 4,
        "name": "marble table lamp",
        "desc": "really cool marble lamp",
        "price": "$27.50",
        "status": "Buy Now"
      },
      {
        "id": 5,
        "name": "vintage walkman",
        "desc": "go back in time with this music player",
        "price": "$5.25",
        "status": "Buy Now"
      }
    ],
    "sold_categories": [
      {
        "id": 6,
        "name": "decor"
      },
      {
        "id": 7,
        "name": "home"
      },
      {
        "id": 8,
        "name": "living room"
      },
      {
        "id": 6,
        "name": "decor"
      },
      {
        "id": 8,
        "name": "living room"
      },
      {
        "id": 7,
        "name": "home"
      },
      {
        "id": 5,
        "name": "electronics"
      }
    ],
    "purchased_categories": [
      
    ]
  }
]