Delphi plugin framework

Question

Hello,

I want to design Delphi plugin framework. There are three options:
1. DLL
2. BPL
3. COM interface

Every option has some disadvantage.

DLL - Promblem with MDI apllication, forms from plugin cannot be embeded to the host exe - mdi application.
BPL - Every *.bpl plugin and *.exe host application must be compiled with the same version of Delphi.
COM - Interfaces {xxx-xx-xxx-xx} must be registered in system, (regsvr) So plugin framework cannot be portable!

Is everything true what I wrote above? If not, please correct me, or is there some other possibility?
thanks

Answer 1

Yes, what you wrote is correct. All of these have advantages and disadvantages, the question is what is important for you, you didn't say what you want to do, so we can't tell you how to do it.

In general, I would pick BPL by default, use DLL if you need to use it from non Delphi apps, and pick COM only if you really have to.

The alternative is to not build your own, since there are several Delphi plugin frameworks available.

Also, this topic has been discussed here before, check out:

• how-best-to-add-plugin-capability-to-a-delphi-program
• plugins-system-for-delphi-application-bpl-vs-dll

Answer 2

Another possibility is having a scripting interface, such as with Python or Pascalscript. There are many advantages to this approach, not least of which is that the plugin source is also the executable, making it easy to debug and share.

Answer 3

I would look at Hydra from Remobjects.

Another candidate would be a combination of PaxCompiler (scripting) and EControl Form Designer (form designer).

Answer 4

We use DLLs, even when using only with a Delphi application. Dll forms are embedded in the main form and use Tabs instead of MDI. For DLL to work properly we also use a shared memory manager and built with runtime packages: vcl, rtl and our own package.