On Thu, 8 Sep 2011, Reinier Olislagers wrote:
Hi list, Possible newbie question so feel free to educate me ;) (Away for some days, so may not read response until back) A patch by Ludo Brands on bufdataset (mantis 19930) got me thinking: const ftSupported = [ftString,ftGuid,... and so on]; procedure TCustomBufDataset.CreateDataset; var i:integer; begin ... // check if all types are supported For i:=0 to FieldDefs.Count-1 do if not (Fielddefs.items[i].DataType in ftSupported) then DatabaseErrorFmt(SUnsupportedFieldType,[Fieldtypenames[Fielddefs.items[i].DataType]]); CreateFields; end; Suppose I want to write a dataset data copier or importer/exporter, how do I detect supported datatypes in a dataset? For example, in my dbfexport test code, I make a bufdataset with all possible fields, then strip each field away when strange errors/AVs occur when assigning values to them. For other datasets (with similar checks as proposed in Ludo's patch), the runtime library is nice enough to warn me on field creation that it doesn't work. Am I missing something obvious or does it make sense to expose something like a SupportedFieldTypes property for datasets? How does Delphi do this?
It does not.
Besides that, I think it's an excellent idea to check for invalid datatypes when creating fields, rather than failing later on when assigning values to them.
It is up to the implementation of the datasets to give a decent error when an unsupported data type is being created. Michael. _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
