Rails 4：如果有记录，则更新而不是新的

Question

Here is my schema...

create_table "documents", force: true do |t|
    t.string   "document_name"
...
  end

  create_table "transcriptions", force: true do |t|
    t.text     "content"
    t.integer  "user_id"
    t.integer  "document_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "users", force: true do |t|
    t.string   "email"
    t.string   "password_digest"
    t.string   "role"
...
  end

Users can create transcriptions of document. I only want users creating one transcription of each document. In my document index view I have...

    <td><%= link_to 'Transcribe', new_document_transcription_path(document, current_user) %></td>

However, with this link the user can create multiple transcriptions of a single document. I have added a model validation that looks like...

  validates_uniqueness_of :document_id, :scope => :user_id

This works to stop multiple transcriptions at the DB. But, ideally I would like a link_to statement such that if no transcription exists for that user/document, then they could create a new one, or if one does exist, when the user clicks "Transcribe" they edit the existing transcription.

Answer 1

You can do a check in the new action

def new
  @transcription = current_user.transcriptions.where(:document => params[:document_id]).first
  if @transcription
    render action: 'edit'
  else
    @transcription = Transcription.new
    render action: 'new'
  end
end