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|Master Detail Screen In OA Framework Part-I||| Print ||
|Written by Anil Passi|
|Monday, 20 August 2007|
I would like to touch base upon an important topic "How to build Master Detail Screens in OA Framework?"
Hence I will cover this topic in a series of articles. In this first part, lets do some comparison vis-a-vis D2K [Oracle Forms].
One of the most common data entry screens used in business is of type MASTER-DETAIL.
We know that is simple to build a master detail screen in D2K Forms or in Apex. It isn't too difficult in OA Framework either.
Lets begin with a high level comparison between Forms(D2k) and OA Framework, for a master detail screen.
Create the base table/view
In case of D2k, the blocks are based either on tables or on Database Views.
In case of OA Framework, both the master and the detail regions will be based on View Objects.
Both these View Objects will be based on Entity Objects, if the data in both Master & Detail regions can be modified.
Create a relation between the two blocks/regions
In Oracle Forms, we create a relationship between the "two blocks". This relation gets created by means of a join.
However in case of OA Framework, the relation does not exist between two regions.
Instead the relationship exists between the two Entity Objects[Association] and also the two View Objects[via View Link]
Note: In this case, by default 3 View Object instances will be created against the Application Module.
1. Master VO Instance
2. Detail VO Instance
3. "Detail VO Instance" attached to "Master VO Instance"
The records in third View Object instance are always kept in sync with first View Object. This synchronization is managed automatically by OA Framework engine.
You will find the details in Audio-Video presentation on this topic, in future parts of this article.
How does OA Framework manage to keep child records in sync with Master record?
Detail View Object keeps listening to the changes in master record navigation.
At any given point in time, there can be only one single record in Master ViewObject, that will be flagged as CURRENT RECORD.
Whenever the current record changes in Master Region, the Child/Detail view object gets Re-Queried.
This is made possible by means of Observer Pattern, please see link for details
In D2K, we can use Key-UP or Key-DOWN to change the current Record in block. Is something similar possible in OA Framework?
I am afraid not [at least for now]. To the master region, you will be adding a "Single Selection Item".
"Single Selection Item" is nothing but a Radio Button against each record in Master Region.
Now to recap:-
1. Master detail screens can be built using Advanced Table of OA Framework.
2. You will create a radio button field on master region.
3. The record for which you select the radio button in Master Region, should be flagged as the Current Record.
In the next article, we will see how to create
a. Entity Objects for both master and detail tables
b. View Objects for the above Entity Objects
c. Create associations between entity objects of Master and Detail
d. Create link between Master & Detail view Objects
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