Rails simple form doen't pass params from input - ruby-on-rails

Question

I want to display a list of InvestorTypes (as a radio button) but before each type I should be able to add an explanation of that type. Here is what I've got:
<%= simple_form_for(resource, as: resource_name, url: users_user_experience_level_path(resource_name), html: { method: :put }) do |f| %>
<div class="form-inputs">
<% User::USER_EXPERIENCE_LEVEL.each do |level| %>
<b>Investor type <%= level %></b>
<%= t("user.description.#{level}") %>
<%= f.input :experience_level, collection: [level], as: :radio_buttons, label: false %>
<% end %>
</div>
<div class="form-actions">
<%= f.button :submit, 'Submit' %>
</div>
<% end %>
Which gives me expected view:
Investor type Beginner
Some explanation of what is going on
[checkobox] type Beginner
Investor type Expert
Some clarification of who is an expert and what ever you want to display here
[checkbox] type Expert
Investor type Institutional
Some clarification of who is an institutional client and some legal stuff
[checkbox] type Institutional
But when Submit button is pressed it doesn't pass input value (radio box selection which user chose) into the params:
=> #<ActionController::Parameters {"experience_level"=>""} permitted: true>
[EDIT]
class User < ApplicationRecord
USER_EXPERIENCE_LEVEL = %w[institutional beginner expert].freeze
end

Answer 1

It looks to me like you're using simple form wrong. The "collection" input in Simple Form is expecting to get an entire list of options, not just one option.
Looping in the way you're doing it is creating one group for each experience level, and each group only has one button in it. So it might visually look correct, but it's not functioning the way you intended. Instead you want to create one group of radio buttons for experience level such that each button changes the value of experience level.
Because you're doing this with significant customization around the appearance, it's probably not a good use of Simple Form, and instead you should fall back to the normal Rails form helpers.

Answer 2

You want to pass a block to f.input to get the simple form wrapper and then use the lower level rails helpers:
<%= simple_form_for(resource, as: resource_name, url: users_user_experience_level_path(resource_name), html: { method: :put }) do |f| %>
<div class="form-inputs">
# adds the simple form wrapper
<%= f.input :experience_level do %>
# iterates across the options and yields a input builder to each iteration
<%= f.collection_checkboxes(:experience_level, User::USER_EXPERIENCE_LEVEL, :value_method, :label_method) do |cb| %>
# There are three special methods available:
# object, text and value,
# which are the current item being rendered, its text and value methods, respectively.
<%= t("user.description.#{cb.text}") %>
<%= cb.check_box %>
<% end %>
<% end %>
</div>
<div class="form-actions">
<%= f.button :submit, 'Submit' %>
</div>
<% end %>
If you don't actually have a model you can use #itself to iterate across a flat array:
<%= f.collection_checkboxes(:experience_level, User::USER_EXPERIENCE_LEVEL, :itself, :itself) do |cb| %>
Or an array of pairs:
<%= f.collection_checkboxes(:experience_level, User::USER_EXPERIENCE_LEVEL.zip(User::USER_EXPERIENCE_LEVEL), :first, :last) do |cb| %>
Or even a struct.