4D v18
CLEAR LIST
- 4D Language Reference
-
- Hierarchical Lists
-
- Managing Hierarchical Lists
- APPEND TO LIST
- CLEAR LIST
- Copy list
- Count list items
- DELETE FROM LIST
- Find in list
- GET LIST ITEM
- Get list item font
- GET LIST ITEM ICON
- GET LIST ITEM PARAMETER
- GET LIST ITEM PARAMETER ARRAYS
- GET LIST ITEM PROPERTIES
- GET LIST PROPERTIES
- INSERT IN LIST
- Is a list
- List item parent
- List item position
- LIST OF CHOICE LISTS
- Load list
- New list
- SAVE LIST
- SELECT LIST ITEMS BY POSITION
- SELECT LIST ITEMS BY REFERENCE
- Selected list items
- SET LIST ITEM
- SET LIST ITEM FONT
- SET LIST ITEM ICON
- SET LIST ITEM PARAMETER
- SET LIST ITEM PROPERTIES
- SET LIST PROPERTIES
- SORT LIST
CLEAR LIST
| CLEAR LIST ( list {; *} ) | ||||||||
| Parameter | Type | Description | ||||||
| list | ListRef |
|
List reference number | |||||
| * |
|
If specified, clear sublists from memory, if any. If omitted, sublists (if any) are not cleared. | ||||||
The CLEAR LIST command deletes the hierarchical list whose list reference number you pass in list.
Usually you will pass the optional * parameter, so all the sublists, if any, attached to items or subitems of the list will be deleted as well.
You do not need to clear a list attached to a form object via the Property List window. 4D loads and clears the list for you. On the other hand, each time you load, copy, extract from a BLOB, or create a list programmatically, call CLEAR LIST when you are through with the list.
To clear a sublist attached to an item (on any level) of another list currently displayed in a form, proceed as follows:
- Call GET LIST ITEM on the parent item to get the list reference of the sublist.
- Call SET LIST ITEM on the parent item to detach the sublist from the list item before clearing it.
- Call CLEAR LIST to clear the sublist whose reference number you obtained with GET LIST ITEM.
Within a clean-up routine that clears all objects and data that you no longer need (i.e., when a window is closed and a form unloaded), you may end up clearing a hierarchical list that may have already been cleared, depending on the user actions within the form. Use Is a list to clear the list only if necessary:
` Extract of clean-up routine
If(Is a list(hlList))
CLEAR LIST(hlList;*)
End ifSee example for the Load list command.
See example for the BLOB to list command.
Product: 4D
Theme: Hierarchical Lists
Number:
377
Created: 4D v6
4D Language Reference ( 4D v18)
