Using variable field and extracting field by attribute in QGIS Modeler

Question

I have a problem while creating a model. I want to extract certain polygons based on a field value (chain of character). The problem is the name of the field might change depending on the origin of the vector layer (but the values are always the same: CD, CC, CC? and 5C).

In my model I put an entry of the model as "vector field", which allow me to choose a field from a vector layer (also an entry of my model), but when I write an expression in the "extract from attribute" algorithm (@Valueofhexagons='CD', with Valueofhexagons the name of my entry variable for the entry vectorfield) it does not extract anything.

When I type the name of the field (from a know vector file I am working on) "AltTB"='CD'... it works perfectly... but I have to change the name manually every time the name of the field change...which I would like to avoid if possible.

Any idea on how to use variables as entry model?

• Gabriel De Luca: Hi. Seems like you are using "Extract by expression" instead of "Extract by attribute" algorithm?

Answer 1

I little late but ...
I had a similar problem but solved it as soon as I posted my question. The variable is being used "as is" rather than as a field name to search in.

attribute(@SearchField) ilike concat('%', @SearchWord ,'%') solved my problem. The attribute() function gets the current value in the field of the name stored in @SearchField.