Rails form populated from one table and saving to another - ruby-on-rails

Question

Title kinda says it all, Basically i have this form
<% provide(:title, "Edit user") %>
<h1>Editing event:
<%= #newevent.id %></h1>
<div class="row">
<div class="col-md-6 col-md-offset-3">
<%= simple_form_for #newevent do |f| %>
<div class="form-group">
<%= f.label :eventname %>
<div class="row">
<div class="col-md-6">
<%= f.text_field :eventname, :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<div class="row">
<div class="col-md-6">
<%= f.input :event_type, :collection => ['Concert','Festival','Sports','Theatre'] %>
</div>
</div>
</div>
<div class="form-group">
<%= f.label :eventdesc %>
<div class="row">
<div class="col-md-6">
<%= f.text_field :eventdesc, :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<%= f.label :eventshortdesc %>
<div class="row">
<div class="col-md-6">
<%= f.text_field :eventshortdesc, :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<%= f.label :pagetitle %>
<div class="row">
<div class="col-md-6">
<%= f.text_field :pagetitle, :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<%= f.label :metatag %>
<div class="row">
<div class="col-md-6">
<%= f.text_field :metatag, :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<%= f.label :eventvenuename %>
<div class="row">
<div class="col-md-6">
<%= f.text_field :eventvenuename, :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<div class="row">
<div class="col-md-6">
<%= f.input :time, type: "time", :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<div class="row">
<div class="col-md-6">
<%= f.input :date, type: "date", :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<div class="form-group">
<%= f.label :eventimage %>
<div class="row">
<div class="col-md-6">
<%= f.text_field :eventimage, :autofocus => true, class: "form-control" %>
</div>
</div>
</div>
<%= f.submit "Save changes", class: "btn btn-info" %>
<%= link_to "Delete", event_path(#newevent), :method => :delete, class: "btn btn-danger" %>
<% end %>
</div>
</div>
Here is what it loads from.
def edit
#newevent = Event.find(params[:id])
end
However its different now. I am wanting the stuff to load form the Master table (so the fields are populated from Master) However i have an update method that looks like this
def update
#newevent = Event.find(params[:id])
if #newevent.update_attributes(event_params.merge createdby: current_user.id)
flash[:success] = "Profile updated"
redirect_to "/events"
else
flash.now[:alert] = 'Error updating event'
end
end
Do i need to change something in the eventparams to get this to work (and make change from Event to Master) The fields are different in both tables, So would i need to make the value of the fields be something like this?
value: "<%=Master.name%>"
Thanks
Sam

Answer 1

If you're trying to load "defaults", you'd be better doing it in the model layer:
#app/models/event.rb
class Event < ActiveRecord::Base
before_create :set_defaults
private
def set_defaults
default = Master.first
self.attributes.except("id", "created_at", "updated_at").each do |field|
self[field] ||= default.send(field)
end
end
end
The above will pull a record from the Master model, populate any of the attributes in your Event model which have not been populated.
However, I believe your pattern to be inefficient.
The idea you are pulling "default" data from another model/table directly contradicts the DRY and modular principles of software development.
Not to say that if you wanted to create "dynamic" defaults for a model, your pattern might work. If you're trying to store exactly the same data in different models, you've got a problem.
I would do the following:
#app/models/event.rb
class Event < ActiveRecord::Base
##defaults: {
x: "y",
y: "z",
z: "0"
}
before_create :set_defaults
private
def set_defaults
self.attributes.except("id", "created_at", "updated_at").each do |field|
self[field] ||= ##defaults[field]
end
end
end
Update
After a discussion, it became apparent that there was more context required to understand the issue/solution fully.
The app works by importing a series of CSV data into the Master table. Whilst I don't know what data this is, the OP said that each Event would be built around the data in Master.
He mentioned he needed 3 fields definitely from Master whilst the others could be inputted by the user into Event.
This means that you could tie the two together with a has_many / belongs_to relationship:
#app/models/master.rb
class Master < ActiveRecord::Base
has_many :events
end
#app/models/event.rb
class Event < ActiveRecord::Base
belongs_to :master
end
This is a standard ActiveRecord association, which means you'll be able to call #master.events & #event.master -- accessing values from each table:
#app/controllers/events_controller.rb
class EventsController < ApplicationController
def new
#event = Event.new
end
def create
#event = Event.new event_params
#event.save
end
private
def event_params
params.require(:event).permit(:master_id, ...)
end
end
#app/views/events/new.html.erb
<%= form_for #event do |f| %>
<%= f.collection_select :master_id, Master.all, :id, :name %>
<%= f.submit %>
<% end %>
--
The reason why this will be much better than your current pattern is that each time you create a new event, you'll be able to access the master attributes:
#event.master.url #-> "url" from master record

Answer 2

In Rails in general you create bound form inputs by using a model and passing it to form_for (or simple_form_for).
In this case if you really need to have dynamic user editable default the most obvious solution would be to use Master to seed the new Event.
In most cases however defaults should be a developer concern which are handled on the model layer as suggested by Rich Peck.
Also setting defaults only really makes sense for a new record - why would you want to override the users choices when updating?
def new
#master = Master.last
#event = Event.new(#master.attributes.except("id", "created_at", "updated_at"))
end
<%= simple_form_for #newevent do |f| %>
<%= f.input :eventname %>
<% end %>