Specifying Information for Exporting

When the Assistant creates a new project, it supplies default values for the attributes that must be specified. Most of these values are set to UNSPECIFIED to indicate that you must modify this attribute. Some attributes do not have a default value because there is no reasonable one; also, supplying a default value could cause the wrappers to be built with incorrect values.

The one value that is set by default in most cases is the Convert Majority flag, used if the value is an array. The default setting for this attribute (True) provides the most expected behavior. For more information, see Converting Array Majority.

Note that in the IDL language, parameters are optional, so the Assistant does not require the user to export every parameter that is retrieved from the IDL source object and presented in the Assistant. It is up to the user to decide which parameters should be exported. This might require defensive programming in the IDL source object to ensure that parameters are not used if they are not supplied.

Information that can be specified includes:

Bridge Information — defines general wrapper object information, the output directory, package name (Java only) and GUIDS settings (COM only)

Source Object Information — indicates whether the object is drawable or not (this cannot be changed)

Property Information — defines the property data type, whether it is an array (and the array majority if it is), and whether or not it is to be exported

Method Information — defines the export characteristics of a procedure or function method, and defines the return value data type and array characteristics if the method is a function

Parameter Information — defines the mutability, data type, array characteristics and export selection for method parameters

Note
See Parameter Passing and Type Conversion for important information about passing objects, arrays and variables as parameters.

About the Export Property

The first (and only the first time) any attribute of a property, method, or parameter other than Export is set, the item has its Export property set to True. This behavior is provided as a convenience.

Converting Array Majority

The Convert Majority property may be an option for a property, function return value or method parameter that is defined as an array (the Array property is True). The rules for the Convert Majority property vary depending on destination (COM or Java) and whether the array is a property value, function return value or method parameter. The settings and default values are described in Table 7-3.

Table 7-3: Rules for Specifying the Convert Majority Property
Where to Specify	Can Specify in COM?	Can Specify in Java?
Get Property	No (arrays always converted)	Yes (default is to convert)
Set Property	Yes (default is to convert)	Yes (default is to convert)
Function return values	No (arrays always converted)	Yes (default is to convert)
Procedure parameters	Yes (default is to convert)	Yes (default is to convert)

See the following for more information on these rules:

Table 7-8 in Property Information

Table 7-10 in Method Information

Table 7-11 in Parameter Information

Note
For COM wrappers, you could theoretically set the Convert Majority flag for the property setting call but not the property retrieval call. In practice, the Assistant uses one flag to control the Convert Majority setting for both Get and Set Property, and so for COM, the setting for properties is always Convert Majority, which is set to True and disabled.

For more information on array majority, see Multidimensional Array Storage and Access. Also see Array Order Conversion.

Supported Data Types

The following data types are supported with the Export Bridge technology.


COM	Unsigned char Char Short Unsigned short Long Unsigned long LONGLONG	ULONGLONG Float Double BSTR IUnknown* VARIANT
Java	JIDLNumber JIDLObjectI JIDLString

Note
See IDL Java Object API for information on JIDL* objects.