Change Layer API

Related with https://github.com/CartoDB/cartoframes/pull/586

Context

We want to change how we currently use the different layers we have:

• QueryLayer
• LocalLayer
• Layer

First Approach

We’ve thought the following solution as a starting point to address this issue. We (backend team) are already working on a Dataset class. This class is going to handle local/remote datasets, but for this issue, I’m going to talk about it as a black box.

Since a Dataset is one of the source types we’ve in CARTO VL, we could have, additionally a SQL or Query class and a GeoJSON class. These clases aren’t our priority for this task at this point, but let’s just imagine we’ll have these “source” classes.

Each layer will have a source class. We’d have a main Layer class, that will receive this source class and a context (we’ll talk later about the contexts).

Then, we’d have three classes that’d inherit from Layer: PointLayer, LineLayer and PolygonLayer. What’s the advantage of having a class per geometry type? First, that we know at first glance the geometry of the layer. But also, that we could implement specific helper methods depending on the geometry, and that’d be very cool.

• Contexts TBD

It’d be useful to provide a context per source, so you can combine both local and remote datasets, for instance. By declaring the context in the map, this is the context the layer would use, but you’d be able to use an specific context for a layer.

For example:

vl.Map([
      vl.PointLayer('dataset_1'),
      vl.PolygonLayer('dataset_2')
   ],
   context=context
)

vl.Map([
      vl.PointLayer('SELECT * FROM dataset_1 WHERE cat = "cat"'),
      vl.PolygonLayer(vl.GeoJSON('file_name.geojson'))
   ],
   context=context
)

To Do

Note: Front + Back should be involved in this task

• Refactor base Layer class
• ~Create PointLayer, LineLayer and PolygonLayer~ ❄️
• Define how to integrate the Source (Dataset)
• Create SQL & GeoJSON sources

Other ToDos moved to https://github.com/CartoDB/cartoframes/issues/629

[oleurud]

After the yesterday talk, @elenatorro and I have talked and we thought there are 2 different tasks/parts in this issue:

• the VL way: the user has the data ready in the database or in a geoJSON/mvt file and the user wants to render a map with vl.source.SQL, vl.source.GeoJSON, …
• the dataframe way: the user wants to make things over the data (using Pandas) and then render a map with the data. To do this, we have 2 options:
  • the user makes over the data (pandas or other ways), then upload the data to CARTO and finally use the VL way to render the map. To do this, if I am not wrong, we don’t have to integrate anything between backend and frontend.
  • the user makes things over the data (pandas) and then the user has a way to send the pandas.DataFrame to VL. To do this, we have to integrate backend and frontend (find a way to send a pandas.DataFrames to VL). The yestarday proposal was talking about this case, because I think having a full local way to render a map is powerful. I want to talk about it with @javitonino & @alrocar. But of course, any feedback is welcome.

[elenatorro]

what is the dataframe source?

From CARTOFrames documentation, it’s a GeoDataFrame --> http://geopandas.org/reference/geopandas.GeoDataFrame.html

keep it simple for now and expand in the future

I’m ok with this, let’s freeze Create PointLayer, LineLayer and PolygonLayer for now. Just pointing that these layers would be a syntax sugar for the Layer class, they wouldn’t require a lot of extra implementation.