Rails 4 - simple form: how do I populate a form field based on the link used to access the form?

Question

I have models in my Rails 4 app for Projects and Interests. The associations are:

Project

has_many :interests

Interest

belongs_to :project
belongs to: user

The purpose of the interest form is for users to register interest in a project.

In my projects show view, I have two links to register interest. Users can express interest in a project either as a participant or as an observer.

In my interest form, I have two boolean fields called :participant and :observer.

I'm trying to figure out how to populate the relevant boolean attribute with 'true', depending on which link the user clicks to get to the form. If they click 'participate in this project', then the participant attribute in the interest table should be set to true.

In my interest form, I have:

<%= f.hidden_field :user_id, @current_user.id %>
<%= f.hidden_field :project_id, @project.id %>

<%= f.input :observe, as: :radio_buttons, :label => "Do you want to monitor this project?" %>
<%= f.input :participate, as: :radio_buttons, :label => "Do you want to participate in this project?" %>

Is there a way that I can auto-complete the observe and participate booleans in this form, based on which link the user follows to access this form, from the projects show?

Routes for interests (it's actually called 'eoi' in my app:

rake routes | grep eoi
                        eois GET       /eois(.:format)                                             eois#index
                             POST      /eois(.:format)                                             eois#create
                     new_eoi GET       /eois/new(.:format)                                         eois#new
                    edit_eoi GET       /eois/:id/edit(.:format)                                    eois#edit
                         eoi GET       /eois/:id(.:format)                                         eois#show
                             PATCH     /eois/:id(.:format)                                         eois#update
                             PUT       /eois/:id(.:format)                                         eois#update
                             DELETE    /eois/:id(.:format)                                         eois#destroy

In the projects show view, I have these links to register interest to participate or monitor a project:

<%= link_to 'Participate', new_eoi_path(@eoi) %>
<%= link_to 'Monitor', new_eoi_path(@eoi) %>

Answer 1

You can pass in whether it is observer or participate in the query string of the form.

Change the route helper that goes to this form to

new_eoi_path(observe: true)

or

new_eoi_path(participate: true)

And then change your inputs in the new view to

<%= f.input :observe, checked: params[:observe],as: :radio_buttons, :label => "Do you want to monitor this project?" %>
<%= f.input :participate, checked: params[:participate], as: :radio_buttons, :label => "Do you want to participate in this project?" %>

Edit

How about using this for the inputs?

<%= f.radio_button :observe, true, :checked => params[:observe] %>
<%= f.radio_button :participate, true, :checked => params[:participate] %>

Answer 2

Add this to your view

<%= link_to 'Participate', new_task_path(@eoi, participate: true) %>

<%= link_to 'Monitor', new_task_path(@eoi, observe: true) %>

And in your controller,

def new
  @task = Task.new
  @participate = params[:participate] # will be nil if observe link was clicked
  @observe = params[:observe]
end

And finally in the forms, set checked to the value based on @observe or @participate

<%= f.input :observe, checked: @observe, as: :radio_buttons, :label => "Do you want to monitor this project?" %>
<%= f.input :participate, checked: @participate, as: :radio_buttons, :label => "Do you want to participate in this project?" %>

EXTRA

If the user clicks on the observe link, you would want to check observe and also uncheck participate . To do so, replace your new action with

def new
  @task = Task.new
  @participate = params[:participate] || false
  @observe = params[:observe] || false
end

This way, if the user clicks on the observe link, the value of yes will be set for observe and no will set for participate .