#import 指令官方介绍 MSDN

#import Directive (C++)

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C++ Specific

Used to incorporate information from a type library. The content of the type library is converted into C++ classes, mostly describing the COM interfaces.

用来去从一个典型库中合并信息。这个典型库的内容将被转换为C++类格式，大多数情况下是用来描述COM接口。

函数声明如下：

#import "filename" [attributes]

#import <filename> [attributes]

Parameters【参数】

filename【文件名】
Specifies the type library to import. filename can be one of the following:

指定这个典型库去导入。文件名可以是下面的一种类型：

The name of a file that contains a type library, such as an .olb, .tlb, or .dll file. The keyword, file:, can precede each filename.

这个包含一个典型库的文件的名字，像.olb,.tlb,或者是.dll文件。关键字在每一个文件名的前面。

The progid of a control in the type library. The keyword, progid:, can precede each progid. For example:

这个典型库中的progid控件。关键字progid:可以在每一个progid的前面。例如：

#import "progid:my.prog.id.1.5"
For more on progids, see Specifying the Localization ID and Version Number.

对于progid上更多的存在库，看指定定位的ID标志以及版本号。

Note that when compiling with a cross compiler on a 64-bit operating system, the compiler will be able to read only the 32-bit registry hive. You might want to use the native 64-bit compiler to build and register a 64-bit type library.

注意当在64位操作系统上进行交叉编译的时候，编译器将只能够对去32位注册集操作。你可能想要去用本地64位编译器去生成和注册64位典型库。

The library ID of the type library. The keyword, libid:, can precede each library ID. For example:

这个典型库的ID。关键字，libid:，可以在每一个库ID的前面。例如：

#import "libid:12341234-1234-1234-1234-123412341234" version("4.0") lcid("9")

If you do not specify version or lcid, the rules that are applied to progid: are also applied to libid:.

如果你不指定版本号或者Lcid，应用到progid的规则也将应用到libid上。

An executable (.exe) file.   一个可执行文件exe。
A library (.dll) file containing a type library resource (such as .ocx).

一个库文件包含一个典型库资源，例如.ocx。

A compound document holding a type library.

一个组件文档支持一个典型库。

Any other file format that can be understood by the LoadTypeLib API.

其他文件格式可以被LoadTypeLib API 所理解。

attributes 【属性】
One or more #import attributes. Separate attributes with either a space or comma. For example:

一个或者更多的导入属性。每个分割的属性中间用空格或者逗号隔开。例如：

#import "..\drawctl\drawctl.tlb" no_namespace, raw_interfaces_only

-or-

#import "..\drawctl\drawctl.tlb" no_namespace raw_interfaces_only

Remarks 【摘要】

Search Order for filename
filename is optionally preceded by a directory specification. The file name must name an existing file. The difference between the two syntax forms is the order in which the preprocessor searches for the type library files when the path is incompletely specified.

文件名是可选的在指定目录之前。文件名必须是存在的文件。在两个不同于法形式的前面是为了提前搜索这些典型库，当路径是被不完全的指定下。

Syntax form  语法格式

Action

Quoted form 引用形式
Instructs the preprocessor to look for type library files first in the directory of the file that contains the #import statement, and then in the directories of whatever files that include (#include) that file. The preprocessor then searches along the paths
shown below.

命令提前去包含这个导入状态的文件目录中查找典型库文件，然后在目录中无论任何包含该文件的地方。

Angle-bracket form

Instructs the preprocessor to search for type library files along the following paths:

The PATH environment variable path list

The LIB environment variable path list

The path specified by the /I (additional include directories) compiler option, except it the compiler is searching for a type library that was referenced from another type library with the no_registry attribute.

Specifying the Localization ID and Version Number

When you specify a progid, you can also specify the localization ID and version number of the progid. For example:

#import "progid:my.prog.id" lcid("0") version("4.0)

If you do not specify a localization ID, a progid is chosen according to the following rules:

If there is only one localization ID, that one is used.

If there is more than one localization ID, the first one with version number 0, 9, or 409 is used.

If there is more than one localization ID and none of them are 0, 9, or 409, the last one is used.

If you do not specify a version number, the most recent version is used.

Header Files Created by Import

#import creates two header files that reconstruct the type library contents in C++ source code. The primary header file is similar to that produced by the Microsoft Interface Definition Language (MIDL) compiler, but with additional compiler-generated code and
data. The primary header file has the same base name as the type library, plus a .TLH extension. The secondary header file has the same base name as the type library, with a .TLI extension. It contains the implementations for compiler-generated member functions,
and is included (#include) in the primary header file.

If importing a dispinterface property that uses byref parameters, #import will not generate __declspec(property) statement for the function.

Both header files are placed in the output directory specified by the /Fo (name object file) option. They are then read and compiled by the compiler as if the primary header file was named by a #include directive.

The following compiler optimizations come with the #import directive:

The header file, when created, is given the same timestamp as the type library.

When #import is processed, the compiler first checks if the header exists and is up to date. If yes, then it does not need to be re-created.

The #import directive also participates in minimal rebuild and can be placed in a precompiled header file. See Creating Precompiled Header Files for more information.

 8etzzkb6.collapse_all(zh-cn,VS.110).gifPrimary Type Library Header File

The primary type library header file consists of seven sections:

Heading boilerplate: Consists of comments, #include statement for COMDEF.H (which defines some standard macros used in the header), and other miscellaneous setup information.

Forward references and typedefs: Consists of structure declarations such as struct IMyInterface and typedefs.

Smart pointer declarations: The template class _com_ptr_t is a smart-pointer implementation that encapsulates interface pointers and eliminates the need to call AddRef, Release, QueryInterface functions. In addition, it hides the CoCreateInstance call in creating
a new COM object. This section uses macro statement _COM_SMARTPTR_TYPEDEF to establish typedefs of COM interfaces to be template specializations of the _com_ptr_t template class. For example, for interface IMyInterface, the .TLH file will contain:

_COM_SMARTPTR_TYPEDEF(IMyInterface, __uuidof(IMyInterface));

which the compiler will expand to:

typedef _com_ptr_t<_com_IIID<IMyInterface, __uuidof(IMyInterface)> > IMyInterfacePtr;

Type IMyInterfacePtr can then be used in place of the raw interface pointer IMyInterface*. Consequently, there is no need to call the various IUnknown member functions

Typeinfo declarations: Primarily consists of class definitions and other items exposing the individual typeinfo items returned by ITypeLib:GetTypeInfo. In this section, each typeinfo from the type library is reflected in the header in a form dependent on the
TYPEKIND information.

Optional old-style GUID definition: Contains initializations of the named GUID constants. These are names of the form CLSID_CoClass and IID_Interface, similar to those generated by the MIDL compiler.

#include statement for the secondary type library header.

Footer boilerplate: Currently includes #pragma pack(pop).

All sections, except the heading boilerplate and footer boilerplate section, are enclosed in a namespace with its name specified by the library statement in the original IDL file. You can use the names from the type library header either by an explicit qualification
with the namespace name or by including the following statement:

using namespace MyLib;

immediately after the #import statement in the source code.

The namespace can be suppressed by using the no_namespace attribute of the #import directive. However, suppressing the namespace may lead to name collisions. The namespace can also be renamed by the rename_namespace attribute.

The compiler provides the full path to any type library dependency required by the type library it is currently processing. The path is written, in the form of comments, into the type library header (.TLH) that the compiler generates for each processed type
library.

If a type library includes references to types defined in other type libraries, then the .TLH file will include comments of the following sort:

//

// Cross-referenced type libraries:

//

//  #import "c:\path\typelib0.tlb"

//

The actual filename in the #import comment is the full path of the cross-referenced type library, as stored in the registry. If you encounter errors that are due to missing type definitions, check the comments at the head of the .TLH to see which dependent
type libraries may need to be imported first. Likely errors are syntax errors (for example, C2143, C2146, C2321), C2501 (missing decl-specifiers), or C2433 ('inline' not permitted on data declaration) while compiling the .TLI file.

You must determine which of the dependency comments are not otherwise provided for by system headers and then provide an #import directive at some point before the #import directive of the dependent type library to resolve the errors.

For more information, see the Knowledge Base article "#import Wrapper Methods May Cause Access Violation" (Q242527) or "Compiler Errors When You Use #import with XML" (Q269194). You can find Knowledge Base articles on the MSDN Library media or at http://support.microsoft.com/support/.
#import Attributes

#import can optionally include one or more attributes. These attributes tell the compiler to modify the contents of the type-library headers. A backslash (\) symbol can be used to include additional lines in a single #import statement. For example:

#import "test.lib" no_namespace \

   rename("OldName", "NewName")

For more information, see #import Attributes (C++).

END C++ Specific