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Overview
About Connections
Overview
Object-oriented programming facilitates development of complex
software systems by breaking them up into a number of much smaller,
simpler program elements called objects. Objects work together by
sending each other messages, that is, by requesting behavior that is
implemented by the target object. Taken as a group, these behaviors
comprise a class interface.
Using an object-oriented approach for complex systems provides the
following benefits:
- Individual classes are much easier to create and understand.
- Systems are much easier to maintain and enhance. Object
implementations can be modified individually without modifying the
rest of the system, as long as the objects continue to respond
appropriately to messages sent to them by other objects.
Despite these benefits, implementing large systems can still be
expensive. One way to reduce the cost is to reuse object
implementations. Many companies would prefer to buy reliable reusable
classes, creating classes only for functions specific to their business.
This vision of constructing custom software using standard building
blocks has been called construction from parts. The building blocks
themselves have popularly been called parts or components
However, reuse is hard to achieve when the class interfaces are too
specific to the application for which they were originally developed. To
promote wider reuse, class interface conventions called component models
have been defined, such as ActiveX, VCL, and JavaBeans.
VCL is the standard component model for the Delphi and C++Builder.
VCL includes the following definitions:
An event model. Event models specify how a component sends
messages to other objects without knowing the exact methods that the
other object implements. This enables a component to be reused with a
range of objects that have different interfaces
Events, properties, and methods. VCL defines a component
interface in terms of the events it can signal, the property values
that can be read and set, and the methods it implements. This
definition provides more structure to the interface of a component
compared with a simple class interface.
The TrueRAD Suite enables you to create programs visually from
existing components. To build a program with the TrueRAD Suite,
you create connections between components in the Connection Editor. The TrueRAD
Suite provides a very sophisticated connection capability to specify
how components will interact to implement functions of the program.
Using connections, much of the behavior of an application can be
specified visually.
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