conversations_controller.rb

  def create
    @conversation_transient_model = ConversationTransientModel.new(conversation_params)
    if @conversation_transient_model.valid?
      recipients = User.where(id: @conversation_transient_model.recipients)
      conversation = current_user.send_message(recipients, @conversation_transient_model.body, @conversation_transient_model.subject).conversation
      flash[:notice] = "Your message was successfully sent!"
      redirect_to conversation_path(conversation)
    else
      flash[:error] = "Errors found!"
      render action: 'new'
    end
  end