[fpc-devel] About TDataSet master/detail design in fpc

[Michael Van Canneyt]

On Fri, 6 May 2005, Luiz Américo wrote:

> I noticed that in the current cvs of fpc it's implemented the master/detail 
> relation between TDataset(s).
> I saw that TDetailDataLink and TMasterDataLink was introduced but I couldn't 
> figure how is supposed to work. I also noticed the abscense of NestedDatasets 
> and DataSetField properties.

They are not yet implemented. But NestedDataset and DatasetField are
ONLY for TClientDataset, and we don't support TClientDataset (yet).

> I'd be glad if someone could explain how the design works and what is 
> expected from a TDataset descendant that support it.

Nothing is expected, i.e. TDataset does not implement anything
concerning master/detail. How could it ?

> I'll try to implement it in TSqliteDataSet.

What you must do is

1. Implement parameter support (TParams/TParam is present).

2. Introduce a Datasource property. Whenever the Datasource changes it's
    data, the detail dataset most close, fill in new parameters, and
    reopen.

2 is not a problem, this is max 50 lines of code. 1 is the problem.

Michael.