I guess everyone who had ever used Delphi’s VirtualStringTree will agree that it is a great control. It is a “virtual” control (your data must be held somewhere else) so I was thinking what data structure is the best suited for such a task? IMO that data structure must support hierarchy, it must be fast and easily expandable. The easiest implementation would be using a record and that’s what most of the documentation which can be found is suggesting. But what if you need to do some fast lookups, calculate totals, etc? What data structure you are using together with VirtualStringTree?
EDIT1: I’m using Delphi 2010.
OK, I’ll try to give some more details about my requirements.
Data size can be very variable, from 1 to thousands of items. Each item can hold multiple string, integer values. I need random access, my data can change many times during the application lifetime. Good performance is very desirable. I also need data saving and reloading.
EDIT2:
Got 1 answer so I’ll try to comment my opinion. Thanks, Dorin for your answer but
I don’t think your structure is very convenient.
1) It doesn’t deal with hierarchy.
2) Having separate TStringList’s or TList’s for each node is not very effective IMO. With this implementation I can only lookup the current node’s data, but can’t effectively search in the whole tree.
I think this data structure must be like a tree. It must have nodes with ability to add children. Then I just could get node’s data in OnInitNode event, check if my node has some children, set ivsHasChildren flag if so, then in OnInitChildren event set correct children count. Later in OnGetText event I could just fetch needed data from my node structure and set it to CellText based on the Column index. My idea is to have a separate data structure and do all the needed operations with it without a need to use VirtualStringTree. Hope someone got my point :).
EDIT3: I’ve found quite interesting JclTrees unit which at first sight could be used to achieve what I’m looking for. It belongs to JCL library. Lack of decent documentation makes it hard to quickly investigate it’s functionality. I’ll probably look deeper into it when I have some more time.
OK, because given answers didn’t solved my issues I’ve written my own tree data structure which imitates TVirtualStringTree and handles all the problems I mentioned in my question. Now I can optionally use only my data structure and all the changes in it will automatically update the VirtualStringTree. I think I will upload source code somewhere later and post the link here. Thanks for all the answers.
EDIT: I’ve uploaded source to the Google code: svTrees. There is a little demo that shows how it works.