[{"event_name":"video_completed","object_id":123456789}]

def self.getEngagementRules(videos)

    rules = []

    videos.each do |video|

        rule = {
            event_name: "video_completed",
            object_id: video.image_hash.to_i
        }

        rules << rule.to_json
    end

    rules
end

puts rules

[{"event_name":"video_completed","object_id":123456789}, {"event_name":"video_completed","object_id":123456789}]