# Implementing project management and event types **URL:** \ **Category:** Rails\ **Created:** [August 19, 2010, 7:54pm UTC](https://www.ruby-forum.com/t/implementing-project-management-and-event-types/193568 "2010-08-19T19:54:02Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![richardsugg](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/5f9b8f/32.png) [@richardsugg](https://www.ruby-forum.com/u/richardsugg)\ **Post date:** [August 19, 2010, 7:54pm UTC](https://www.ruby-forum.com/t/implementing-project-management-and-event-types/193568/1 "2010-08-19T19:54:02Z")
I am implemented a simple project management application. Each project has various events, and each event can be a different type. Some event information is common, such as name, start date, close date, and comments. I have a projects table which has\_many events. My plan is to have several sub-event tables, like event\_get\_access which will contain an event\_id field to link it to table events as well as information specific to a “get access” event (remote access, username, passwords, etc). Another event type might be “upgrade” which stores information about the server to be upgraded, etc. So I have: - a project which has\_many events - events which belongs\_to :project - sub-events which belong\_to :event How do the subevents relate to event? An event will never have more than one subevent, but it may not have any of a particular subevent. Thanks for your help on this? ---
**Author:** ![richardsugg](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/5f9b8f/32.png) [@richardsugg](https://www.ruby-forum.com/u/richardsugg)\ **Post date:** [August 19, 2010, 7:59pm UTC](https://www.ruby-forum.com/t/implementing-project-management-and-event-types/193568/2 "2010-08-19T19:59:19Z")
May be my ---
**Author:** ![richardsugg](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/5f9b8f/32.png) [@richardsugg](https://www.ruby-forum.com/u/richardsugg)\ **Post date:** [August 19, 2010, 8:02pm UTC](https://www.ruby-forum.com/t/implementing-project-management-and-event-types/193568/3 "2010-08-19T20:02:14Z")
may be my option wrong. if I do your project i will do this. - a project which has\_many events - events which belongs\_to :project event has\_one sub\_event option II - a project which has\_many events - events which belongs\_to :project sub\_event has column “sub\_event\_id”. it just refer the sub\_event table On Fri, Aug 20, 2010 at 12:57 AM, Sampath M. \ **Author:** ![richardsugg](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/5f9b8f/32.png) [@richardsugg](https://www.ruby-forum.com/u/richardsugg)\ **Post date:** [August 19, 2010, 9:51pm UTC](https://www.ruby-forum.com/t/implementing-project-management-and-event-types/193568/4 "2010-08-19T21:51:43Z") On 19 August 2010 18:52, richardsugg [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > So I have: > > - a project which has\_many events > - events which belongs\_to :project > - sub-events which belong\_to :event > > How do the subevents relate to event? An event will never have more > than one subevent, but it may not have any of a particular subevent. Have you looked at Single Table Inheritance, which would allow multiple types of event all in one table (rather than have subevents of different types)? Otherwise I think you could have Event has\_one :sub\_event\_type\_one has\_one :sub\_event\_type\_two and so on. Then SubEventTypeOne belongs\_to :event etc. It does not matter if a particular event does not have a particular type of subevent, if you try to access event.sub\_event\_type\_one and it does not have one then you will get nil Colin ---
**Author:** ![richardsugg](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/5f9b8f/32.png) [@richardsugg](https://www.ruby-forum.com/u/richardsugg)\ **Post date:** [August 23, 2010, 3:19pm UTC](https://www.ruby-forum.com/t/implementing-project-management-and-event-types/193568/5 "2010-08-23T15:19:17Z")
Sorry for the delay – I forgot to subscribe to the thread and didn’t realize I had responses until I checked manually. I thought about STI, but it seems that I would have a very complex table. I did not realize, however, that I could include a bunch of has\_one statements – I assumed that since an event would have a particular subevent based on the event\_type, that the has\_one wouldn’t work. Since it will (just have to check for nil and know which event\_type I’m working with), I think your second opinion would work. Thanks!