Overview of component creation

This chapter provides an overview of component design and the process of writing components for Delphi applications. The material here assumes that you are familiar with Delphi and its standard components.

• Class library

• Components and classes

• Creating components
• What goes into a component?

• Creating a new component

• Testing uninstalled components
• Testing installed components

• Installing a component on the Component palette

For information on installing new components, see “Installing component packages” on page 16-10 of the Developer’s Guide.

Class library

Delphi’s components reside in a component library that includes the Visual Component Library (VCL) and the Component Library for Cross-Platform (CLX). Figure 1.1 shows the relationship of selected classes that make up the VCL hierarchy. The CLX hierarchy is similar to the VCL hierarchy but Windows controls are called widgets (therefore TWinControl is called TWidgetControl, for example), and there are other differences. For a more detailed discussion of class hierarchies and the inheritance relationships among classes, see Chapter 2, “Object-oriented programming for component writers.” For an overview of how the hierarchies differ from each other, see “WinCLX versus VisualCLX” on page 15-7 of the Developer’s Guide and refer to the CLX online reference for details on the components.