How to define a Form Override for a Chained Form Field in Active Scaffold

Question

Below example is taken from this documentation page:
https://github.com/activescaffold/active_scaffold/wiki/Chaining-Form-Fields

[Example start]
You can set an array of columns to update multiple columns when a column changes, and chain column updates:

class UsersController < ApplicationController
  active_scaffold do |config|
    config.columns[:author].form_ui = :select
    config.columns[:author].update_columns = [:book, :editorial]
    config.columns[:book].form_ui = :select
    config.columns[:book].update_columns = :format
  end
end

In this example, fields for book, editorial and format are updated when author changes, and when book changes only format is updated. A form override which use the new author or book must be defined for editorial and format columns, in other case those fields won’t change when they will be rendered again. [Example end]

In the example it states "a form override which use the new author or book must be defined".

Question is how to define those form overrides ??

I have read the documentation on https://github.com/activescaffold/active_scaffold/wiki/Form-Overrides, and tried different form overrides, but with no luck so far, i.e. the columns are not being rendered again.

If you can help me with the code for those form overrides needed in the given example, then I should be able to port that to my code.

Answer 1

Here is the solution to my problem:

I followed the example on "https://github.com/activescaffold/active_scaffold/wiki/Chaining-Form-Fields", but when it did not work for my chained columns (when updating the first column all chained columns updates correctly, but when updating the second column then its chained columns renders to blank lists), then I focused (blindly?) on the details explained just below the example as I thought this was the first step to solve my problem: "A form override which use the new author or book must be defined for editorial and format columns, in other case those fields won’t change when they will be rendered again".

This was however not the case, no form override in the helper was needed to get this to work, in the helper the "options_for_association_conditions" is enough. As the example is for v2.4, maybe the form override is not needed anymore in v3.0+.

The solution is in the next paragraph on the example wiki: "Usually only the value of the changed column is sent, if you need another values to render the updated columns, enable send_form_on_update_column and all the form will be sent". My problem was, that the columns which was chained from the second column needed the value from the first column also, so setting up the second column with "send_form_on_update_column" (i.e. sending the whole form, not just its own value) solved my problem.

In the example this would be:

config.columns[:book].send_form_on_update_column = true