Let’s assume that I have such a simple database scheme:

CREATE TABLE tbl(key INTEGER PRIMARY KEY, cap TEXT NOT NULL); 

I want to show at least three independent GUI windows. One window (window A) with list of items, if I choose one item it should be possible to open window B, that allow delete or update item. Also it should be possible to open window B to create new item. Ordinary task for many applications I suppose. But I want to make window B to be not modal dialog, plus allow to create several window B type dialogs.

How should I make coherent content of these windows?

For example if I create:

struct Record {   int64_t id;   std::string text; }; 

and class Db that encapsulate simple update, select, insert and delete SQL statements it would be not enough.

Because of for example I can open window B with last item in tbl, maximum value of key column, that open again it in other window B, and delete it, after that create new item, and this item will get that same key value as deleted one. So I have two window B with the same key, but different cap.

Should I create in Db class cache with std::shared_ptr<Record>? And add possibility to subscribe on std::shared_ptr<Record> changes?

Or may be there is other standard way to handle situation like this?