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...or what to do if
VB reaches its limits
Introduction:
VB是一种胶强大的语言，VB支持现代的所有技术
is a very powerful language, that supports nearly all modern
technologies. What makes VB so powerful? I think, that there are three
major reasons for that:
vb通过COM组件可扩展.其他语言中编写COM组件，在VB中调用Using
components written in other languages lets you use the vigorousnesses of
these languages with VB.
对VB最大的批判是他自身处理缓慢与其他语言相比（C++,
Delphi, Smalltalk等），但是为什么不用VB作为应用程序的框架,关键过程在其他语言中写.The
main criticism to VB is, that the native VB language commands are
processed slower than in other languages (e.g. C++, Delphi, Smalltalk
etc.) But, hey, why not use VB as framework for your application and
write time critical functions in another language? This could make your
VB application rock. Take my GameAI-Lib as a living example for such a
task.
向你展示在VC++中写COM组件并应用于VB程序In
this article, I will show you, how you can create a COM-component using
Microsoft Visual C++ 6.0 and how you can use it within your VB
application. The only things you need are the compilers (VB and VC) and
a little C++ knowledge. You will see, it will be very easy.
Getting started: 现在开始
First, we will create a project in VC++:首先，创造一个VC++工程
选择File->New在Projects选项卡中选
ATL COM AppWizardFrom，工程名为"MyLib"这个名称也将会是
COM-DLL的名称。 the VC++ IDE menu choose File->New and activate
the tabpage "Projects". From the procets-list choose "ATL
COM AppWizard". Give our baby a name. I named our lib "MyLib".
This will be the name of the COM-DLL and will also be the name of the
TypeLib as you will find it in the VB references list.
按"OK" 后 VC 向导会创建ATL COM工程，ATL
的意思是活动模板库。After that, press "OK" and VC
AppWizard will create a ATL COM Project for us. ATL means Active
Template Library and consists of a set of C++ template classes that make
implementing COM objects and interfaces much easier.
下一步选择“动态连接库”意味着它将与VB应用程序运行在同一线程中。我们的组件依托于"atl.dll"中，它要方在windows/system目录。如果在其他机器上运行，需要再注册。In
the next step of the AppWizard choose "Dynamic Link Library(DLL)"
as servertype. This will generate a in-process COM-component for us,
that means, it will run in the same process environment as our VB
application. Our component will have dependencies to the "atl.dll"
which is stored in your windows/system folder. You need to redistribute
and register it if you want to install your app on another machine. You
could also enable "MFC"-support, but if you do this your
component will have dependencies to the mfc dlls too. We won't do this.
Now press "Finish" and after that
"OK". Your project and the source files will be created.
如下：Our project workspace will now look
like this:
Forget about that functions, I will not explain
them and you will not need them.
我们的类库没有任何对象，要添加一个。要更多对象方法也一样。Let
it breath: Now we have a library without any objects in it. Let's
add our first object (in this tutorial, we will only use one object, but
added more objects works analogically to this).
MyLib类上右键，选择"New ATL
Object..."。MyLibMove your mouse over the MyLib classes root node
and press the right mouse-button. From the context menu choose "New
ATL Object...".
在"objects"对象类别中用"Simple
Object"作为对象。In the next dialog choose the
"objects" category and mark "Simple Object" as
object. Press next.
输入对象名MyObject，类名CMyObject，它将在VB中看到。Enter
a short name for your object (this is VC++ internal, you won't see this
in your VB app). I choosed "MyObject". VC++ will create a C++
class names "CMyObject" from this COM-object. You could rename
it, but we will keep that name. You can specify the name of the CoClass
at the "CoClass" textbox. This will be the name of the
COM-object as it appears in the interface description. That means, this
will be the name of the object as you will see it in VB. Press
"OK".
可以看到结构"CMyObject()"和交换见面"IMyObject"，我们要向其中加入内容。Here
is our object. As you see, it only has a constructor "CMyObject()"
and a interface "IMyObject". We will now add a function to our
object. This function should implement a loop, that adds x times a value
to 0 and then return the result. So this is a multiply realised by
adding a value. Later on we will use this function to measure the time
that our C++ function takes and compare it with VB.
过程将得到两个参数The function should
get 2 parameters.
lValue as Long lCount as Long
rc as Long
右键单击节点选择“添加方法”Move
your mouse over the interface node and right-click it. From the
popup-menu choose the option "Add Method...".
方法名我用"Calculate"，它会在VB中看见，参数如下：Give
our method a name. I took "Calculate". This will also the name
as you will see it in the VB IDE. Type in our parameter list:
long lvalue, long lcount, [out, retval] long* rc
O.K., I think the first 2 parameters are clear
if you understand a littlebit about C++. But why is there a third input
parameter with such a funny declaration? And where is our return
parameter?
你要通过指针获得结果。COM interface
functions always have the same format: They have a variable list of
parameters and also return a return-code as HRESULT. If the HRESULT
isn't S_OK the function failed and a COM error is raised. The VC++ IDL
(Interface Decription Language) compiler interpretes the parameters
[out, retval] and declares the parameter as an out-parameter and as the
(one and only) return value. You must pass the variable as a pointer,
because this is the only way to get data out of this function. That's
the whole magic.
双击它，添加如下代码This is what our
function looks like. Double-click it and the VC++ IDE brings you
directly to the source of that function. Enter the following code:
STDMETHODIMP CMyObject::Calculate( long lvalue, long lcount, long *rc)
{
long lresult = 0;
for ( long i = 0; i < lcount; i++)
{
lresult = lresult + lvalue;
}
*rc = lresult;
return S_OK;
}
编译Compiling:
We are finished. The last thing we have to do is compiling the
component.
编译 选"Win
32 - Release MinSize"（菜单：编译->编译 MyLib.dll），VC++会编译编译组件并注册Choose
the compile option "Win 32 - Release MinSize" and compile your
program (menu: Build->Build MyLib.dll) The VC++ compiler will build
your component and register it, so it is ready to use.
在VB中：创建一工程，添加一按扭，选择工程->引用
选你的组件Using
it with VB: Create a new VB project and add a button to it. From
the menu, choose project->references and pick our component:
在按扭中加入代码：Press
OK and you are ready to use the library in our sample VB project. Within
the button-code add the following code:
Dim oMyObject As New MyObject
MsgBox Format(oMyObject.Calculate(2, 5000000))
未完成，你可以添加更多的Now we are
ready with this tutorial. Try the Sample (check the link at the button).
In the sample, I have implemented the same functionality in VC++ and in
VB. Compare the speed of both version. But try it more than once,
because our VC is loaded for the first time into memory. This will cause
our first execution a littlebit slower. Remember, that this calculation
is pretty uncomplex. You can get a lot more out of it.
I hope this tutorial will help you develope
VC++ COM-objects for VB. If you have any question about using other
data-types than "long", ask me or take a look at msdn online
or the VC++ online manual (OLE types).
在VC++中调试组件：在VB中创建project1.exe，在VC++设置编译选项"Win
32 - Release MinSize" 变为 "Win 32 - Debug"。Tip
- Debugging our component with VC++: How can I debug this object
if it is used from VB? This is easy: Make an executeable (project1.exe)
from your VB project. In VC++ set the compile option from "Win 32 -
Release MinSize" to "Win 32 - Debug".
运行程序，在代码中设置短点，当程序运行，在VC++中可看到停在短点处Specify
the VB project.exe as executeable for the debug session and set a
breakpoint in your code. Now press "F5" to "run"
your component. After that the VB application is started and if you
reach the breakpoint the VC++ debugger will stop at the C++ code. That's
it.
Download the source:
You can download the source of the tutorial here.
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