Teach Yourself Borland C++ in 14 Days - portal

TIP
C++Builder Database Architecture
You can drag TFields from the Fields Editor directly onto a form. This
will create a data-aware control and a corresponding label on the form.
You can configure which data-aware component is dropped onto the
form using the TControlClass property in the Database Explorer.
TFields also support implicit data conversions. That is, you don’t have to know what type
of data a TField actually stores to convert it to another data type. This is facilitated by TField’s
Value property. Value is a variant type that is implicitly converted when it is assigned or
receives a value. For example, you can assign a string to a boolean field using its Value variant,
like so:
TBooleanField MyBoolean;
...
MyBoolean->Value=”T”;
You can also assign a numeric field to a string control using its Value property:
TCurrencyField MyMoney;
...
Edit1->Text=MyMoney->Value;
TField’s amazing ability to implicitly convert between different data types makes it
chameleon-like in its capacity to adapt to varying data requirements. This simplifies your
applications and makes for less work when an application’s underlying data structure
changes.
Summary
As you can see, the C++Builder database class hierarchy is rich, yet easy to use. Great attention
has been given to making the hierarchy not only extensive, but also coherent. The VCL
database classes strike a good balance between functionality and ease of use.
Workshop
The Workshop contains quiz questions to help you solidify your understanding of the
material covered and exercises to provide you with experience in using what you have learned.
You can find answers to the quiz questions in Appendix A, “Answers to Quiz Questions.”
471
12