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AsBoolean

property AsBoolean: Boolean read write;

Example​

function IsEnabled(const Data: TvxClientDataSet): Boolean;
begin
  Result := (not Data.FieldByName('Enabled').IsNull) and
    Data.FieldByName('Enabled').AsBoolean;
end;

Usage​

AsBoolean reads or writes a field through its field's Boolean conversion, with null, text and unsupported-type behaviour determined by that field class.

  • Prefer this member for TBooleanField or a field whose DataType contract explicitly supports Boolean conversion.
  • Do not use truthiness assumptions for arbitrary strings; validate the accepted source representation.
  • Treat conversion, range, read-only, not-editing and OnValidate failures as normal exceptions.

Additional Technical Info​

AsBoolean is the Boolean conversion contract declared by hidden TField. The runtime object returned by FieldByName is normally a concrete Delphi field descendant; that descendant, not the PascalScript helper, performs the conversion.

Source-backed behaviour​

The runtime helper delegates directly to native TField.AsBoolean. Base TField.GetAsBoolean and SetAsBoolean both raise a field-access EDatabaseError, so the property is usable only when the actual descendant implements the conversion. TBooleanField reads and writes its native Boolean buffer. Delphi string fields also implement a conversion: reading is true only when the first character is T, t, Y or y; other text, including False, reads false, while Boolean writes use the descendant's string representation.

Concrete numeric and variant fields may provide additional conversions. A null Boolean-capable field normally reads the descendant's default Boolean (False), which loses the distinction between null and false; check IsNull first when that distinction matters. Writes require a client dataset write state and can invoke field validation and change notifications.

Official RTL references​

Created 2026-07-15