Visual Basic Reference
Coffee consists of a client, CoffWat2, and two ActiveX components (OLE servers), Coffee2 and MTCoffee. Together, these three projects demonstrate:
- Asynchronous notifications using events (Coffee2).
- Asynchronous notifications using call-back methods (Coffee2).
- Multithreading (MTCoffee).
XTimers.vbp is a helper project that provides a code-only timer used by Coffee2 and MTCoffee.
This is an expanded version of the project developed in the step-by-step procedures in Chapter 3, "Creating an ActiveX Exe Component," in Creating ActiveX Components. For more information on asynchronous notifications and multithreading, see ."
|CoffWat2.vbp||The CoffeeWatch client project.|
|CWMod1.bas||Startup code for the project.|
|CWForm1.frm||The clients main form.|
|ICoffNot.cls||The ICoffeeNotify interface used for call-back methods..|
|CWNotMe.cls||NotifyMe object implements the ICoffeeNotify interface, so it can receive call-backs.|
|CWThread.frm||Client form for demonstrating multithreading.|
|CWCofTrk.cls||The CoffeeTracker object is used to wait for completion events from the multithreaded Coffee object.|
|AboutCof.txt||A copy of this document, demonstrating the ability to store related documents in a project.|
|Coffee2.vbp||The Coffee2 component project.|
|Co2Cmon.cls||The CoffeeMonitor class used to demonstrate asynchronous notifications using events.|
|Co2Conn.cls||The Connector class that enables multiple clients to share a CoffeeMonitor object.|
|Co2CMon2.cls||The CoffeeMonitor2 class used to demonstrate asynchronous notifications using call-back methods.|
|Co2Conn2.cls||The Connector2 class that enables multiple clients to share a CoffeeMonitor2 object.|
|Co2Mod1.bas||Holds a reference to the shared CoffeeMonitor and CoffeeMonitor2 objects.|
|MTCoffee.vbp||The MTCoffee component project.|
|MTCoffee.cls||The multithreaded Coffee object.|
|MTCMod1.bas||A standard module for demonstrating instancing of global data.|
|XTimers.vbp||The call-back timer project.|
|XTimer.cls||The XTimer object.|
|XTimerS.bas||Support module for XTimer.|
Although there's not a lot of code in it, this is a complex sample to run, because it demonstrates out-of-process components. For debugging, an out-of-process component must be run in a separate copy of Visual Basic.
In addition, the sample demonstrates features multithreading and code-only timers that either cannot be demonstrated in, or are dangerous to run in, the development environment.
- Load XTimers.vbp (which is listed in the Samples directory) into Visual Basic. On the File menu, select Make XTimers.dll to make the project into a .dll file.
DO NOT run XTimers in the development environment at this time. XTimers must be compiled because it uses Windows APIs for a code-only timer object.
- Load MTCoffee into Visual Basic. On the Project menu, select References to open the References dialog box. Select XTimers and click OK, to set a reference to the compiled DLL.
- On the File menu, select Make MTCoffee.exe to make the project into an .exe file.
DO NOT run MTCoffee in the development environment at this time. You need to make the project into an executable because the development environment cant support multiple threads of execution if you run MTCoffee within Visual Basic, it wont display multithreading behavior.
- Load Coffee2.vbp into Visual Basic. On the Project menu, select References to open the References dialog box. Select XTimers and click OK, to set a reference to the compiled DLL.
- Press CRTL+F5 to run the Coffee2 project.
Use CRTL+F5 instead F5 of when running an out-of-process component project, to ensure that all compile errors are caught before the component is supplying objects to the client. (See "Creating an ActiveX Exe Component" in Component Tools Guide.)
- Start another instance of Visual Basic, and load CoffWat2.vbp. On the Project menu, select References to open the References dialog box. Select Coffee2 (make sure you get the entry for Coffee2.vbp) and MTCoffee (make sure you get the entry for MTCoffee.exe), and then click OK, to set references to the components.
- Press F5 to run the project.
After running the sample application and observing the behavior of MTCoffee when it allocates a separate thread for each Coffee object, you may find it instructive to recompile MTCoffee after changing the threading to a round-robin thread pool. (You can find this option in the Unattended Execution box, on the General tab of the Project Properties dialog box.) When using a round-robin thread pool, you can observe blocking and global data sharing between objects on the same thread.
You can also compile Coffee2.exe and CoffWat2.exe, and run multiple clients, to observe sharing of the asynchronous notification objects CoffeeMonitor and CoffeeMonitor2. With multiple clients, the round-robin thread pool means blocking and data sharing between objects in use by different clients.
To understand what's going on in this sample, see "Building Code Components," in Creating ActiveX Components.