Ted, I agree 100% with Ken. Inheritance is the *wrong* thing to use in this situation. Using a Role with a many-to-many relationship to Person is the right way to do what you want. What is especially great about this pattern is that it makes it easy to switch what role(s) a Person has at runtime depending on the current context you are using them in. The Role entity itself could use inheritance if need-be, but in general I avoid using inheritance. It certainly is the right thing to do sometimes but be very cautious.
Dave Sent from my iPhone > On May 19, 2014, at 4:10 AM, Ken Anderson <kenli...@anderhome.com> wrote: > > I’m not familiar with ERXPartials, but I would second the use of a role > pattern. I typically use this pattern for both people and companies. > > To elaborate, you can have a table/entity - Person. You then have a number > of Role entities (WorkerRole, SupervisorRole) that inherit from a Role > entity, where WorkerRole, SupervisorRole, and any other roles, use a single > table (single table inheritance). Then you have a to-many relationship from > Person to the Role entity. > > You can use validation to enforce any business rules you have (like a person > can’t be both a supervisor and worker at the same time). > > In this manner, you can have all the immutable attributes of a Person in one > place, and all their role data (like maybe the supervisor’s head count) in > the role where it makes sense. > > An important downside of a Person entity with a sub entity of Worker and > Supervisor - what happens when the worker gets promoted? EOF HATES IT if you > try and modify the entity of a particular object. That means that you end up > deleting John the Worker and adding John the Supervisor, destroying any > history you had of John (like to pay records, infractions, etc). > > Good luck! > > Ken > >> On May 12, 2014, at 2:50 AM, Timothy Worman <li...@thetimmy.com> wrote: >> >> Ted: >> >> Rather than inheritance, I use ERXPartials for this. Have one database >> entity for ‘Person’ and various types of persons as partials. One database >> row has all of the attributes of the different types. >> >> If not partials, I probably prefer the role pattern to inheritance. >> >> Tim >> UCLA GSE&IS >> >>> On May 11, 2014, at 1:02 PM, Theodore Petrosky <tedp...@yahoo.com> wrote: >>> >>> I am starting a project. I need to manage assets (people). But people will >>> be both a User of the system and the managed asset. >>> >>> Also a person could be an employee of a company that needs to manage the >>> assets. >>> >>> So I thought I would create a person class and do inheritance. >>> >>> a worker inherits from a person >>> a supervisor inherits from a person >>> >>> Am I going nuts and too deep with inheritance? Would it be easier to have a >>> single entity person that has booleans to identify workers or supervisors. >>> I mean a person could be both a worker and supervisor. >>> >>> maybe just talking about it will help me think if through. >>> _______________________________________________ >>> Do not post admin requests to the list. They will be ignored. >>> Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) >>> Help/Unsubscribe/Update your Subscription: >>> https://lists.apple.com/mailman/options/webobjects-dev/lists%40thetimmy.com >>> >>> This email sent to li...@thetimmy.com >> >> >> _______________________________________________ >> Do not post admin requests to the list. They will be ignored. >> Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) >> Help/Unsubscribe/Update your Subscription: >> https://lists.apple.com/mailman/options/webobjects-dev/kenlists%40anderhome.com >> >> This email sent to kenli...@anderhome.com > > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/webobjects-dev/webobjects%40avendasora.com > > This email sent to webobje...@avendasora.com
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