Call FieldByName to retrieve field information for a field when only its name is known. FieldName is the name of an existing field. FieldByName returns the TField component for the specified field. If the specified field does not exist, FieldByName raises an EDatabaseError exception.

FieldName can be the name of a simple field, the name of a subfield of an object field that has been qualified by the parent field's name, or the name of an aggregated field. Because of this flexibility, it is often preferable to use FieldByName rather than the Fields property.

An application can directly access specific properties and methods of the field returned by FieldByName. For example, the following statement determines if a specified field is a calculated field or not:

if Customers.FieldByName('FullName').Calculated then
  MessageDlg(Format('%s is a calculated field. ',
   ['FullName']),
   mtInformation,
   [mbOK],
   0);

FieldByName is especially useful at design time for developers who are creating database applications, but who do not have access to the underlying table and therefore cannot use persistent field components.

To retrieve or set the value for a specific field, call the default dataset method FieldValues instead of FieldByName.