Record bookmarking
Marking and Returning to Records
In EhLib before version 8.1 TMemTableEh.Bookmark object stored data in the form of a record number. Starting with version 8.1 the TMemTableEh.Bookmark property stores data as a pointer to the record object in the internal array of records. This allows you to uniquely identify a record when filtering, sorting, or deleting data in TMemTableEh.
To see a new possibilities of using Bookmarks in DBGridEh look at a Demo project in the folder –DEMOS\DBGridEh.MemTable.Bookmarks
Due to changes in the method of storing data in Bookmarks the SearchPanel of DBGridEh component no longer supports searching within the selected records. Instead DBGridEh allows you to filter the data through SearchPanel without losing the list of selected records in the grid. To make the selected records not be cleared when navigating through DBGridEh when sorting set the dghClearSelection value in the TDBGridEh.OptionsEh property.
In addition to moving from record to record in a dataset (or moving from one record to another by a specific number of records), you can mark a particular location in a dataset so that you can return to this location. TDataSet introduces a bookmarking feature that consists of a Bookmark property and five bookmark methods. In TMemTable, bookmarks contain the record number (RecNo property).
The Bookmark property.
Bookmark gets or sets the current bookmark in a dataset. A bookmark marks a location in a dataset so that an application can easily return to that location quickly.
An application can read Bookmark to retrieve the bookmark associated with the current record, and it can change the current record in the dataset by assigning a saved bookmark value to this property.
GetBookmark method
We do not recommend to use this method, use Bookmark property instead of it. See VCL documentation for detail.
GotoBookmark and BookmarkValid method
When passed a bookmark, GotoBookmark moves the cursor for the dataset to the location specified in the bookmark. Before calling GotoBookmark, you can call BookmarkValid to determine if the bookmark points to a record. BookmarkValid returns True if a specified bookmark points to a record.
CompareBookmarks method
You can also call CompareBookmarks to see if a bookmark you want to move to is different from another (or the current) bookmark. If the two bookmarks refer to the same record (or if both are nil), CompareBookmarks returns 0.
FreeBookmark method
This method is Used in combinations with GetBookamrk. I do not recommend to use this method. See VCL documentation for detail.
function BookmarkToRec(Bookmark: TUniBookmarkEh): TMemoryRecordEh;
function RecToBookmark(Rec: TMemoryRecordEh): TUniBookmarkEh;
Type of TUniBookmarkEh class depends on the version of Delphi and can be TBookmark, array of Byte or TBookmarkStr type.