async version of models serializer

[uside]

No description provided.

[coveralls]

Coverage decreased (-1.4%) to 95.714% when pulling 6d69cb8 on uSide:develop into 7cad89a on adonisjs:develop.

[RomainLanz]

Hey @uside!

Thanks for your contribution! ❤️

May you add some tests to your PR?

---

Previous discussion:

Vladimir Kleshko @uside Jan 23 17:21
hey guys! do you plan to implement computed properties with generators support?

Harminder Virk @thetutlage Jan 23 17:44
@uside Can u share the use-case on what exactly you are trying to achieve?

Vladimir Kleshko @uside Jan 23 18:38
for example, I want computed property for my model where I can fetch data from redis

[thetutlage]

@uside I am not in favor of async computed properties. I asked for the use case to understand what exactly you are trying to achieve. Fetching data from redis is not a computed property at all and should be handled by your application.

[uside]

@thetutlage okay, another simple example: I have some async service and want to retreive data from it without saving this data to db. Sure, this is not a "best practice" for large data, but for small selections it will be nice I think

[thetutlage]

Yeah then you should make use of your controller to fetch the data, Why you want to keep it on the model instance?

[RomainLanz]

Let me provide an example.

So you have your PostsController.index method where you want to display information about your posts.

{% for post in posts %}
  {# ... #}
  {{ post.view_count }}
  {# ... #}
{% endfor %}

The attribute view_count is stored in a Redis database, so the code above will not works.

You can do the same by using your controller to fetch the data from Redis and then you need to map the data.

{% for post in posts %}
  {# ... #}
  {{ redisData[post.id] }}
  {# ... #}
{% endfor %}

[uside]

@thetutlage to reduce number of cycles and make code cleaner. If you have some tree data it will be a big controller like: load data from db -> call toJSON, where lucid map all relations/etc -> load data from async service -> another big map to extend result json. In this case we dont have code in model, but in result we will have a heavy controller

[thetutlage]

@RomainLanz Yes this is less expensive than hitting redis for each record that you fetch from database.

For example: If you have 30posts inside database, the computed property will make 30 calls to redis server for each post instance.

Also if their is complexity in the code, it is better to abstract that logic to usable service, instead of replying on computed properties.

Plus using lodash you can easily map things out, without hitting the performance bottlenecks

[RomainLanz]

@uside Doing asynchronous task in a loop is not recommended. You will end up with a O(n) issue.

As @thetutlage said, if you have 30 posts you will need to do 30 requests to your service/database. That's why we eager/lazy-load relation.

You need to fetch those remote data (with one request if possible) from your controller and create a dictionary/hash to retrieve them in your view.

I have written an example above.

[uside]

I have no more arguments. Close a pr ?

[thetutlage]

If you feel your code is getting unmanagable, feel free to throw the actual situation you are in the gitter room and we all can discuss about it.

But async computed properties will case performance issues no matter what. Closing the PR for now