How to display the attributes of a related entity.

15 Dec '14, 01:15 PM
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Hello,

Other than the default User, Group and Module entities, I have 3 more: Payment, Student and Course as shown in this image: http://imgur.com/9oOOEyu. I would like to show the attributes of connected entities, specifically, the name of the course paid for and the name of the student paying within the list of payments (Here's a snapshot of my model: http://imgur.com/TTF01fG). I have tried importing them from the  "displayed attributes" but my list ends up looking like this: http://imgur.com/BRddsyW. Kindly help me.

 

Thanks.

 
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Hi Aestimo,

Try to add derivate fields in the Payments table refering the name's needed. For instance, in Payments table add derivate student.name and course.name.

Hope it helps.

By the way, are developing an app for learning courses? Could you share with me your user name on Skype to try to talk since I'm developing an app to do exams online

Regards

 
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Sorry I mean add into the domain model not in physical tables. Regards

 
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Hello Martin,

Thank you for that answer, I'll try it out and let you know what comes up. Regarding the exam app that you are developing, of course I'd be interested to connect with you as am still learning how to use Webratio and I think that would be a great way to learn; my Skype name is: aestimo.njuguna (But since I'll be away on holiday as from 19/12/2014, I may not be reachable on Skype, but you can always find me on email at: aestimo.njuguna[at]gmail[dot]com).

 

Thanks and kind regards,

Aestimo.

 
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Hi Martin,

Thanks by the way for the answer. I've tried what you said, I added an attribute ("Student name") on the Payment entity and when I go to the field's derivation properties and I choose "simple imported attribute", the "Payment" option has no expandable arrow for me to choose the derivate student.name (kindly see this screenshot to see what I mean: http://imgur.com/RVPqfID).

 

Thanks.

Aestimo.

 
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Hi Aestimo, 

you cannot define derived attributes on N-N relationships.

In order to solve your problem, follow these steps for each relationship:

  1. Delete the N-N relationship from your Domain Model
  2. Add the bridge entity in your Domain model and map it manually on the corresponding bridge table in your database (both bridge tables already exist in your DB)
  3. Set the two foreign key columns as the primary key of the entity
  4. Draw two 1-N relationships connecting the new entity with the ones connected through the old N-N relationship. The 1 cardinality is referred to the role of the relationship having the new entity as target.
  5. Map manually the two 1-N relationships using the existing column of the new entity as the foreign key and its oid column as oid of the other entity.
  6. Launch the warning on the Domain Model to be sure that there are not mistakes.

If you want to learn more about this topic please refer to the following online lesson:

 

https://www.webratio.com/learn/learningobject/extending-the-domain-model-derivation

 

 

 
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