ArcGIS Engine Developer Guide

VISUAL C++
The main use of #import is to create C++ code for interface definitions and
GUID constants (LIBID, CLSID, and IID) and to define smart pointers. The
exclude (OLE_COLOR, OLE_HANDLE, VARTYPE) is required because
Windows defines these to be unsigned longs, which conflicts with the ArcGIS
definition of long—this was required to support Visual Basic as a client of
ArcObjects, since Visual Basic has no support for unsigned types. There are no
issues with excluding these.
You can view the code generated by #import in the type library header (.tlh) files,
which are similar in format to a .h file. You may also find a type library implementation
(.tli) file, which corresponds to a .cpp file. These files can be large but
are only regenerated when the type libraries change.
There are many type libraries at ArcGIS 9 for different functional areas. You can
start by importing those that contain the definitions that you require. However,
#import does not automatically include all other definitions that the imported
type library requires. For example, when importing the type library esriGeometry,
it will contain references to types that are defined in esriSystem, so esriSystem
must be imported before esriGeometry.
A complete list of library dependencies can be found in the Overview topic for
each library.
Choosing the minimum set of type libraries helps reduce compilation time, although
this is not always significant. Here are some steps to help determine the
minimum number of type libraries required:
1. Do a compilation and look at the “missing type definition” errors generated
from code, for example, ICommand not found.
2. Place a #import statement for the library you need a reference for into your
stdafx.h file. Use the LibraryLocator utility or component help to assist in this
task.
3. Compile the project a second time.
4. The compiler will issue errors for types it cannot resolve in the imported type
libraries; these are typically type definitions, such as WKSPoint or interfaces
that are inherited into other interfaces. For example, if working with geometry
objects, such as points, start by importing esriGeometry. The compiler will
issue various errors such as:
c:\temp\sample\debug\esrigeometry.tlh(869) : error C2061: syntax error :
identifier 'WKSPoint'
Looking up the definition of WKSPoint, you see it is defined in esriSystem.
Therefore, importing esriSystem before esriGeometry will resolve all these
issues.
Below is a typical list of imports for working with the ActiveX controls.
#pragma warning(push)
#pragma warning(disable : 4192) /* Ignore warnings for types that are
duplicated in win32 header files. */
#pragma warning(disable : 4146) /* Ignore warnings for use of minus on
unsigned types. */
Chapter 4 • Developer environments • 121