Progress
External Program
Interfaces
4GL Mechanisms
Ultimately, the differences between COM objects and widgets require separate but related mechanisms in the 4GL to work with them. The most fundamental of these mechanisms are the handles you use to access COM objects and widgets. You must access widgets with widget handles and COM objects with component handles. These handles have different data types that represent the different capabilities that they support—the WIDGET-HANDLE data type for widget handles and the COMPONENT-HANDLE (or COM-HANDLE) data type for COM objects.
COM-HANDLE values have a data type that is compatible with most other Progress data types. For component handles, Progress does the data conversion automatically, unlike widget handles which require the use of Progress data conversion functions, like STRING or INTEGER.
Table 7–1 compares each type of object (COM object and Progress widget) and summarizes how it is supported in the 4GL.
For more information on Progress widgets and the 4GL mechanisms for managing them, see the information on widgets and handles in the Progress Programming Handbook . The rest of this chapter describes the equivalent mechanisms that support COM objects.
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