This is an exchange I had with someone recently and wanted to know if someone could verify that the assertions sound reasonable. Any additional insight/references welcome as well. There are a couple gaps where there was proprietary information, but the gist of it is here. Thanks!
ME: What do you know about creating/using COM servers in VFP?
THEM: you just create object
THEM: then use it like any other foxpro object
ME: have a VFP9 service that I wrote that now needs to be used if possible, or at
least the class it utilizes, in the EM app, called from code/form (@...SAY) to send
data to a port. I would like to use the same class that only works in VFP9 - someone
said it could be done using a COM server.
THEM: if you create an instance of the com object in fms at the start of the main
routine then it will be available as a global object in any routine and you should be
able to call its methods
THEM: you can build a com object as an exe or as a dll
ME: which is preferred and why?
THEM: the dll is called an in process com object. when started it runs within the
memory and treading of the calling exe. the good part is it is fast the bad part is
if it blows up it takes the exe with it.
THEM: an exe is called an out of process com object it runs in its own memory and and
own thread. which means interprocess comunication wich is slow. but if it blows up it
does not nessicarily take down the exe
ME: Pretty much what I though - I might try to go with the dll then. How are those
registered, etc?
THEM: i dont think you need to register it as long as it is in the same dir as the exe
but im not sure about that
ME: I think you may be right - that sounds familiar. So, a dll is just like an exe as
far as how I develop it in VFP? Just how I compile it that is different? Can I take a
visual class, drop it on a non-visible form and just reference it in my code?
ME: Or do I even need the form?
ME: The problem is that the class that i'm using was not written by me - it has properties
methods unavailable for editing - I would like to reuse this class in the next part of my
development. The class is visual, not code based
