Style a feature in one layer based on an attribute in another layer in Print Composer Atlas

Question

I have two layers; one is the foreground and the other a background. Both layers have fields containing similar values (field values in the foreground layer (mun_code) is also present in the background layer's fields (ADM3_PCODE). For instance, both fields may contain the value 012802000).

For the background layer, I am trying to use Rule-based styling to add a thicker border using the expression:

@mun_code = attribute( $currentfeature, 'ADM3_PCODE' )

but @mun_code returns NULL (most likely because mun_code as a field is only present in the foreground layer while the background layer contains the field ADM3_PCODE):

Rule-based styling problem

I already Generated an atlas choosing the foreground layer as the Coverage layer. My understanding is that $currentfeature (in the code above) is already automatically controlled by the Print Composer Atlas, so I am wondering why it returns NULL.

How can I fix this?

• Inactivated Account: maybe some of this might help: gis.stackexchange.com/questions/173399/…
• JAT86: Thank you very much for the info. I managed to fix it using one rule having the expression "ADM3_PCODE" = attribute( @atlas_feature , 'mun_code') for feature of interest and another rule "ELSE" for features of no interest on the background layer.
• Inactivated Account: There are other filters for doing intersects, etc. within the atlas feature layers... very powerful!

Answer 1

@ is for QGIS integrated reserved variables ... i think u meant "mun_code" (keeping the double quotes) to reference the attribute value ... But your aim remains unclear to me : Did u build any relation between the two tables ? Relation based on attributes (has any join been setup ?) or based on geography ? If u want to test the content of an attribute located in another table you have to define a clear relation.

• JAT86: Thanks. I did a table join, and also used double quotes but no difference. I think the main problem is like in this question: gis.stackexchange.com/questions/290844/… but the answers did not do any difference neither.