setFilter() specify key that's within an array of objects

[admly]

I am trying to create a code that is setting filtering based on a key extracted from a GeoJson property which is an array of objects. As I know it is not possible.

So some feature has properties:

properties: {
      'someProperty': [
        {'something': 'A'}, {'something2':'B'}
       ]
    }

this.map.setFilter('points2', ['==', 'someProperty[0].something', 'A']));

Will there be any support for such a filtering? Maybe there is already some workaround for this? Or maybe I am using a wrong syntax?
Cheers

[ryanhamley]

We recommend using the newer expression syntax instead of filters. What you're trying to do can be achieved with an expression.

Consider this example source that includes a property which is an array of objects:

"properties": {
    "someProp": [
        {"foo": "heyooo it works!"},
        {"foo": "b"},
        {"foo": "c"}
    ]
}

Now in our layer's layout properties, we can define the text field like this:

"text-field": ["get", "foo", ["at", 0, ["get", "someProp"]]],

This expression (reading from right to left) get the array at properties.someProp, then gets the element at the 0th index in the array, then gets property foo from that object. You would see heyooo it works! at the text on the map.

Hope this helps and thanks for using Mapbox!

[admly]

@ryanhamley Thanks for answering. In meantime I actually modified my properties a little bit so it looks like this:

"properties": {
    "someProp" : {
         "A": ["X", "Y", "Z"],
         "B": ["W", "Y", "D"],
     }
}

Now:

['match', 'X', ['get', 'A', ['get', 'someProp']], true, false]));

actually returns false. Could you tell me what's wrong with this one?

[ryanhamley]

@admly The way your expression is set up, it's getting someProp.A which is the array ["X", "Y", "Z"]. The expression then tries to match the string value "X" against the array value, which returns false. Think of it like this "X" === ["X", "Y", "Z"] // false.

What you want in this case is the new in expression operator which lets you determine if an item is in an array(or a substring is in a string).

['in', 'X', ['get', 'A', ['get', 'someProp']]]

This is equivalent to someProp.A.indexOf('X') >= 0.

Unfortunately, the in operator is only in the master branch right now. It will be in our beta release next week and included in v1.6.0 the week after that.

[admly]

@ryanhamley YES! I tried to use the in operator, but there was an error in console (saying something that arrays are not supported or sth). But yea, I used 1.5.0 release, so the new feature was not included in it. THANK YOU FOR SUPPORT!!!