Function field in table_query

Support Developer
1

Hello again Tryton community !
This topic is linked to this one where I discussed on how to display a “group by” table in a tree view. I am trying to implement this solution suggested by ced, but I am experiencing some difficulty (I am new to Tryton).
I would like to implement a model based on a table_query, which would return the table of purchases group by party and the sum on the total_amount column.

I noticed that I could not select the total_amount field, because, as a function field, its value is not stored in the database, so there is no total_amount column in the Purchase table.

My question is : what could I implement to manage to display the value of this field in my table_query ? I tried to create a new field with an on_change_total_amount method to store the value of total_amount in a field stored in the database. But apparently I cannot base an on_change method on a function field too…

So what could be a solution to display a function field in the list of a model based on a table_query ?
Thank you for your help, and sorry for the vocabulary mistakes if there are any.

2

As the value of this field is not stored in the database, you will need to add a function field to your model to calculate its value. Perhaps you can take some inspiration from: modules/sale: 8848150a4586 sale_reporting.py

If you only care about purchases that are confirmed, done, or cancelled, then you may be able to use the value in the total_amount_cache column from the database.