Teach Yourself Borland C++ in 14 Days - portal

470 Day 12
Table 12.28. continued
TDateTimeField Date and time values.
TDateField Date values.
TTimeField Time values.
TBlobField Variable-length field with no size limit.
TBytesField Variable-length field with no size limit.
TVarBytesField Variable-length field up to 65,535 characters.
TMemoField Variable-length text field with no size limit.
TGraphicField Variable-length graphics field with no size limit.
You never specifically drop a TField descendant on a form. As mentioned, these are created
for you, either via the Fields Editor or automatically when a TDataset is opened.
Tasks
TFields support a number of column-based settings that you can use to customize your
applications. You specify these settings using the Fields Editor of a TDataset. You access the
Fields Editor by right-clicking a TDataset component and selecting Fields Editor from the
pop-up menu.
For example, to prevent modifications to a field, right-click its TDataset, select Fields Editor,
and then set the field’s ReadOnly property to true in the Object Inspector. To make a field
invisible in a DBGrid, set its Visible property to false. If you want to control the types of
characters allowed in the field, specify a mask in its EditMask property. To change the database
field to which the TField is linked, change its FieldName property to the field you want to
reference.
NOTE
TField Descendant Type of Data Stored
Note that TField’s Visible property only controls whether a column
appears in a DBGrid component if no columns have been defined using
the grid’s Columns property.