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Re: Attempt to insert null key into a com.webobjects.foundation.NSMutableDictionary
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Re: Attempt to insert null key into a com.webobjects.foundation.NSMutableDictionary


  • Subject: Re: Attempt to insert null key into a com.webobjects.foundation.NSMutableDictionary
  • From: Jevon Hills <email@hidden>
  • Date: Thu, 15 May 2003 08:28:10 -0600

On Wednesday, May 14, 2003, at 04:18  PM, Art Isbell wrote:

On Wednesday, May 14, 2003, at 11:58  AM, Jevon Hills wrote:

Sorry Art, I'm still learning. What do you mean 'underlying relationships of a flattened relationship are class properties'?

A flattened relationship spans an entity that's related to the source and destination entities of the flattened relationship. If you look at the definition of the flattened relationship, you'll see that it's comprised of a couple of relationships. These relationships shouldn't be class properties.


I have two tables joined by a 'link table' , I flattened the relationship in eomodeler by selecting the CollectionDesc entity, them the relationship to Collection (the link) and then the relationship to Content and flattened on that so that now my CollectionDesc has methods to set/get Content objs.

Have I done that part correctly??

Possibly not. You should allow EOModeler to create this many-to-many relationship for you. Select the model entry at the top of the entities list in the left pane of EOModeler. In the right page will be the list of entities in the model. Command-select (or if Windows, do whatever supports multiple selections) the CollectionDesc and Content entities. In EOModeler's menu, click "Join in Many to Many" (not sure of the exact wording). This will create the join entity, CollectionDescContent, and all of the necessary relationships. But you'll notice that CollectionDesc.collectionDescContents and Content.collectionDescContents are not class properties. If you need to follow these relationships in your app to access CollectionDescContent, then you'll have to delete the flattened relationship and make these relationship class properties because the flattened and underlying relationships can't all be class properties.


You'll probably want to replace the Collection entity with CollectionDescContent.

I have just created the CollectionDescContent by allowing EOModeler to perform the "join in Many to many", but I'm unsure of a few things, and perhaps this is because I did not give enough of the right info at the beginning for you.


First the more I learn about EOModeler the more I try to find a way to get training on WO. I only know what I've learned using online/web tutorials and books. Apparently that just scratched the surface. Thank-you for your help I do really appreciate it.

Now for more of how I'm confused. I probably did not state at the beginning that I'm working using a corporate database, which is not only used for WO, but by several different tools. As a result I the relation ship of CollectionDesc<-->>Collection<<-->Content is that of 3 tables which I have to use/maintain.

So having followed your instructions I have the following questions:
Can I get CollectionDescContent entity that EOModeler created to maintain the table of Collection for me?


As far as terminology, can you direct me to a good source on the Web which can help me better understand 'Properties' and other elements of WO? Up until now I assumed, and it appears incorrectly, that Properties were synonymous with "Attributes", "Member Data", "Fields" (.NET lingo).

As far as reference materials that I have on hand: WebObjects Developer's Guide by Ravi Mendis, Building WebObjects 5 Applications by Jesse Feiler, Professional WO 5 (Wrox Press). Are there any others you would recommend?



Wow,  sorry about the lack of cohesion.

Jevon
'Hungry for Knowledge'

Aloha,
Art
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Jevon K. Hills
Developer - Zymeta Media Promotion Systems
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 >Re: Attempt to insert null key into a com.webobjects.foundation.NSMutableDictionary (From: Art Isbell <email@hidden>)

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