Duplicating record as default fields in form

Question

I have an object called Formula which can serve as a Master Formula to many Child Formulas.

I want to create a link to "Create Child Formula" on the Master Formula's show page. I did so as follows:

<%= link_to 'Create Child', new_formula_path(:command => "create child", :parent_id => @formula.id) %>

And in my FormulaController I have:

def new
    if params[:command].blank?
      @formula = Formula.new
      @formula.formulation_line_items.build
    elsif params[:command] == "create child"
      @formula = Formula.find(params[:parent_id])
    end
end

And it successfully renders the new page with the form filled-out with the Master's data, allowing the user to edit whichever fields they need.

But without Formula.new under the "create child" branch, it only accepts the form as an Update and not a Creation. (it's the new action and renders new.html.erb, but form button is for Update Formula).

How can I solve this problem? Is there just a way to force POST instead of PATCH so the button creates a new record instead of updating the existing one?

Answer 1 · 2015-07-29T21:20:51Z

July 29, 2015 9:20pm

You can use the dup method on a model instance to create a copy of it which can then be manipulated (by editing the form) and saved as a new record.

  @formula = Formula.find(params[:parent_id]).dup

This is just a shallow copy however as stated in the documentation:

Duped objects have no id assigned and are treated as new records. Note that this is a “shallow” copy as it copies the object’s attributes only, not its associations. The extent of a “deep” copy is application specific and is therefore left to the application to implement according to its need. The dup method does not preserve the timestamps (created|updated)_(at|on).

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Patrick Montalto

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Duplicating record as default fields in form

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Geoff Parsons

Geoff Parsons