# start_new_modal.rb

def self.payload(trigger_id)
    {
      trigger_id: trigger_id,
      view: {
        type: "modal",
        callback_id: "unique-id",
        title: {
          type: "plain_text",
          text: "Start",
          emoji: true
        },
        submit: {
          type: "plain_text",
          text: "Submit",
          emoji: true
        },
        close: {
          type: "plain_text",
          text: "Cancel",
          emoji: true
        },
        blocks: [
          {
            block_id: "conversation",
            type: "input",
            label: {
              type: "plain_text",
              text: "Channel"
            },
            element: {
              action_id: "ml_conversation_input",
              type: "conversations_select",
              response_url_enabled: true,
              placeholder: {
                type: "plain_text",
                text: "Start typing #channel"
              }
            }
          },
        ]
      }
    }
  end

#  actions/task.rb

SlackRubyBotServer::Events.configure do |config|
  config.on :action, "block_actions" do |action|
      payload = StartNewModal.payload(trigger_id)
      slack_client.views_open(payload)
  end
end

# actions/start_new_modal.rb

SlackRubyBotServer::Events.configure do |config|
  config.on :action, 'view_submission', 'unique-id' do |action|
   # nothing comes here
  end
end