Rails - How to add pagination to Fastjson api? - ruby-on-rails

Question

The default result of rendering FastJsonApi gem serialized_json like below:
render json: FlashcardSerializer.new(flashcards).serialized_json
would be something like this:
{
"data": [
{
"id": "1",
"type": "flashcard",
"attributes": {
"question": "why?",
"answer": "pretty good",
"slug": null
}
},
{
"id": "2",
"type": "flashcard",
"attributes": {
"question": "What is 0",
"answer": "it is 0",
"slug": null
}
}
]
}
I would rather add some extra information especially for pagination and I like the result to be something like this:
{
"data": [
{
"id": "1",
"type": "flashcard",
"attributes": {
"question": "why?",
"answer": "pretty good",
"slug": null
}
},
{
"id": "2",
"type": "flashcard",
"attributes": {
"question": "What is 0",
"answer": "it is 0",
"slug": null
}
},
"count":100,
"page":1,
]
}
I am aware of other available gems that manage pagination in API, and I know how to do it without Fastjson. The main issue here is that is there any way to get the aforementioned result from this gem without changing a lot in the code. Thanks

Answer 1

The desired document would be invalid according to the JSON API specification. You would need to include next and previous links in a link section. The current and total_count would belong in the meta section.
{
"data": [
{
"id": "1",
"type": "flashcard",
"attributes": {
"question": "why?",
"answer": "pretty good",
"slug": null
}
},
{
"id": "2",
"type": "flashcard",
"attributes": {
"question": "What is 0",
"answer": "it is 0",
"slug": null
}
},
]
"meta": {
"page": { "current": 1, "total": 100 }
},
"links": {
"prev": "/example-data?page[before]=yyy&page[size]=1",
"next": "/example-data?page[after]=yyy&page[size]=1"
},
}
Have a look at the JSON API specification before you continue designing the API.
You can pass these information into the serializer as an options argument
class FlashcardsController < ApplicationController
def index
render json: FlashcardSerializer.new(
flashcards, { links: {}, meta: { page: { current: 1 } }
).serialized_json
end
end
How you generate the data depends what you use to paginate.
If you design a new API, I would also recommend to use cursor based pagination rather than offset pagination because of it's limitations.
https://github.com/Netflix/fast_jsonapi#compound-document
https://github.com/Netflix/fast_jsonapi/blob/master/spec/lib/object_serializer_spec.rb#L8-L32