The contents of a particular drop down datawindow depends on the value of another drop down datawindow.
For example we need to filter some employees based on the team they belong to. In the current datawindow, Teams will be a drop down datawindow whose contents depend on the value of another DDDW – Departments.
Will assume the datasource of the datawindow containing the two dddws, named t_filter, contains team_id and department_id columns having the generic value of 0 (where the id in both teams and departments tables start with 1).
We create two datawindows with following datasources and link properly to each dddw:
SELECT departments.id AS department_id, departments.description AS department_description FROM departments UNION (SELECT 0 AS department_id, '-' AS department_description FROM t_filter LIMIT 1)
SELECT teams.id AS team_id, teams.department_id AS department_id, teams.description AS team_description FROM teams WHERE teams.description_id = :adepartment_id UNION (SELECT 0 AS team_id, 0 AS department_id, '-' AS team_description FROM t_filter LIMIT 1)
The rest of the code will be in the filter window.
We declare a datawindowchild as instance variable. The department variable will hold the last department selection to avoid unnecessary database traffic.
DataWindowChild dwc; int department;
When the datawindow is retrieved will have to avoid the retrieval argument request, right before the main retrieve call, in the Open() event (dw_main is the container datawindow control placed in the filter window):
CONNECT USING SQLCA; dw_main.SetTransObject(SQLCA); dw_main.GetChild("team_id", dwc); dwc.InsertRow(0); dw_main.InsertRow(0); dwc.SetTransObject(SQLCA); dw_main.Retrieve();
If the user selects a different department, the content of the teams dddw child will have to be updated. In the ItemChanged event:
if GetColumnName() = "department_id" then int val; val = Integer(this.GetText()); if val != department then department = val; dwc.Retrieve(val); end if </code>end if
The problem so far is that if the teams drop down gets filtered and the user has previously selected a value which will be out of filter range, the drop down will still display the old id value. Will avoid this issue extending the pbm_dwndropdown and pbm_ncpaint events.
event ue_dropdown; if GetColumnName() = "department_id" then dw_main.SetRedraw(false); dw_main.SetColumn("team_id"); dw_main.SetText("-"); dw_main.SetColumn("department_id"); dw_main.SetRedraw(true); end if event ue_ncpaint; dwc.Retrieve(this.object.data[1, nDepartmentsColIndex]);
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