Null in MemoField to Variant

[mariot]

Hi,

When we used UniDAC 7.3.10, then with using TDataSet.FieldByName MySQL returns correctly Null value in column COLUMN_DEFAULT in table INFORMATION_SCHEMA.COLUMNS. With new UniDAC 8.1.2 is returned empty string - it is bad value.

I look at more deep, and see that problem is probably in method:

Code: Select all

function TWideMemoField.GetAsVariant: Variant;
begin
  Result := GetAsString;
end;

GetAsString return always string - but I expect Null value as Result of GetAsVariant method.

I assume it's a bug.

Now, in our code, i use workaround:

Code: Select all

// Result is Variant
  Field := (Dataset as TDataset).FieldByName(FieldName);
  if Field.IsNull then
    Result := Null
  else
    Result := Field.Value;

Regards,

Mario

[ViktorV]

This behavior originates from the specifics of the IDE functionality, not UniDAC. When you call the AsVariant method in a descendant class of TField, the implementation defined in the DB unit is called. You can see it for yourself by running your example in RAD Studio 10.2 -- you'll get the exact same result in UniDAC 7.3.10 and UniDAC 8.1.2.
Note that in RAD Studio 10.3, this method was implemented correctly.

[mariot]

Oh, I understand. It is not problem in UniDAC. Thanks for answer.

[ViktorV]

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