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Re: NSDictionary, EOComboBoxController, and EOAssociation subclassing
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Re: NSDictionary, EOComboBoxController, and EOAssociation subclassing


  • Subject: Re: NSDictionary, EOComboBoxController, and EOAssociation subclassing
  • From: Brent Shank <email@hidden>
  • Date: Mon, 27 Jan 2003 13:21:44 -0800

Bill,

I think your data model may be complicating things. If you have an entity called GradingScheme, it could have two significant attributes: gradingKey and gradingKeyDescription. In the client app, you display only the gradingKeyDescription in the combo box. The user's selections then automatically end up storing key-value pairs in the database. The "keys" in this case are the gradingKeys, and the "values" are the key's descriptions. I don't understand why you're storing NSDictionaries in the userInfo for each attribute. That just seems overly complicated. But perhaps you have other reasons for doing it this way?

I don't think you'll get very far implementing EOValueSelectionAssociation and overriding setValueForAspect. In most cases, when you think you have to resort to drastic measures like this, most often something is wrong with the application's data model.

So, if you can rework the data model and database schema, you can get the effect you want without writing more code. Feel free to send me your EOModel if you think that will help me better understand the problem.

Brent

On Monday, January 27, 2003, at 06:23 AM, William Butler wrote:

I am trying to get EOComboBoxController to work with an NSDictionary, such that the values are displayed to the user but it is the key that is read from and stored to the database according to the selected value. One can override newAssociation in EOComboBoxController to have it use the "SelectedIndex", "SelectedTitle" or "SelectedObject", but neither of these is what I need.

I work in the healthcare field, where there many many grading schemes (I='Stubbed toe without abrasion', Ib='Stubbed toe with epidermis abrasion'...etc--you get the picture). I store the NSDictionaries in userInfo() for each EOAttribute. It was pretty easy to get it to work with html D2W. Out of the box D2JC wants you to use to use a to-one relationship for this, but would entail large numbers of entities for me since many of my fields reflect a grading scheme, so I'd rather use the existing NSDictionaries. One could probably override many accessor methods in the client side enterprise objects to do this, but this seems clunky to me.

So my understanding is the D2JC 'wants' you to override EOValueSelectionAssociation to do this, but there isn't enough documentation on how to do it nor are there examples. I tried it by overriding setValueForAspect and valueForAspect, but this caused the client side program to dump with a 'Bus error' message.

Does anyone else have any ideas on how to do this? I'm coming at things from the WO side, so EOAssociation is a new concept for me. It may be that folks coming from the Cocoa side are fluent with this problem.

Thanks,

Bill Butler
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References: 
 >NSDictionary, EOComboBoxController, and EOAssociation subclassing (From: William Butler <email@hidden>)

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