Example: using two DataStores to process data
Suppose you have a window called w_multi_view
that shows multiple views of the same result set. When the Employee
List radio button is selected, the window shows a list of employees
retrieved from the database:
When the Employee Salary Information radio button is selected,
the window displays a graph that shows employee salary information
by department:
This window has one DataWindow control called dw_display.
It uses two DataStores to process data retrieved from the database.
The first DataStore (ids_emp_list) shares its
result set with the second DataStore (ids_emp_graph). The
DataWindow objects associated with the two DataStores have the same result
set description.
When the window or form opens
When the window or form opens, the application sets the mouse
pointer to the hourglass shape. Then the code creates the two DataStores
and sets the DataWindow objects for the DataStores. Next the code
sets the transaction object for ids_emp_list and
issues a Retrieve method to retrieve some data.
After retrieving data, the code shares the result set for
ids_emp_list with ids_emp_graph.
The final statement triggers the Clicked event for the Employee
List radio button.
This code is for the window’s Open event:
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SetPointer(HourGlass!) |
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ids_emp_list = Create DataStore |
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ids_emp_graph = Create DataStore |
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ids_emp_list.DataObject = "d_emp_list" |
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ids_emp_graph.DataObject = "d_emp_graph" |
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ids_emp_list.SetTransObject(sqlca) |
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ids_emp_list.Retrieve() |
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ids_emp_list.ShareData(ids_emp_graph) |
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rb_emp_list.EVENT Clicked() |
Code for the Employee List radio button
The code for the Employee List radio button (called rb_emp_list)
sets the DataWindow object for the DataWindow control to be the
same as the DataWindow object for ids_emp_list.
Then the script displays the data by sharing the result set for
the ids_emp_list DataStore with the DataWindow control.
This code is for the Employee List radio button’s
Clicked event:
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dw_display.DataObject = ids_emp_list.DataObject |
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ids_emp_list.ShareData(dw_display) |
Code for the Employee Salary Information radio button
The code for the Employee Salary Information radio button
(called rb_graph) is similar to the code for the List radio
button. It sets the DataWindow object for the DataWindow control
to be the same as the DataWindow object for ids_emp_graph.
Then it displays the data by sharing the result set for the ids_emp_graph
DataStore with the DataWindow control.
This code is for the Employee Salary Information radio button’s
Clicked event:
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dw_display.DataObject = ids_emp_graph.DataObject |
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ids_emp_graph.ShareData(dw_display) |
When the window or form closes
When the window closes, the DataStores get destroyed.
This code is for the window’s Close event:
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Destroy ids_emp_list |
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Destroy ids_emp_graph |
Use garbage collection
Do not destroy the objects if they might still be in use by
another process—rely on garbage collection instead.