I’m sorry to bring this one up again but it was touched upon in regards to
management operators and auto free objects. Please bear with me while I recap.
To summarize what I said last time was that I wanted a way to include “with”
statement functionality in classes and records to aid in delegation patterns
(in leu of multiple inheritance in Pascal). As it turns out the idea is
relevant to management operators and something similar using properties was
requested by the developer of management operators (Maciej).
He suggested a “default” property which would basically delegate methods/field
calls to another class so to avoid having to do things like "obj._.Free” which
would be shorted to “obj.Free” because the field “_” is default. As he pointed
out if such a default property existed I could leverage management operators to
auto manage objects instead of adding anything more to the compiler like I did
in my version. That’s a really important advancement for FPC and I’m personally
very motivated in seeing this manifest in the language.
Maciej’s example:
TAutoCreate<T: class> = record
_: T;
property obj: T read _; default;
class operator Initialize(var a: TAutoCreate<T>);
class operator Finalize(var a: TAutoCreate<T>);
class operator Copy(constref a: TAutoCreate<T>; var b: TAutoCreate<T>);
class operator AddRef(var a: TAutoCreate<T>);
end;
My suggestion I made some months ago is functionally identical except I wanted
to add a “with” modifier to fields with no explicitly defined limit (or make it
a section like public, or what ever, I don’t care really). i.e:
type
TSomeManager = record
procedure ManageThis;
end;
type
TOtherManager = record
procedure ManageThat;
end;
type
TMyRec = record
delegateA: TSomeManager; with;
delegateB: TOtherManager; with;
end;
var
c: TMyRec;
c.ManageThis; // delegateA is “with” so we can access it’s fields from TMyRec
c.ManageThat; // delegateB is “with” so we can access it’s fields from TMyRec
I’m writing this email today because I just had this exact same problem in my
code and I’m desperate to make this work better in Pascal. :) Making auto free
work as intended would be amazing also but we need to pass this hurdle first.
Thank you for bearing with me, so finally here are my questions:
1) Given this is critical to make management operators work smoothly what does
the compiler team think about this idea to have a default property or “with" in
classes/records?
2) If there is any plausible way the compiler team will allow this I’m willing
to develop it myself to what every specification the team decides. I already
looked into how this could be implemented and did some tests. It’s not
complicated and within the range of something I could accomplish.
Please let me know what you guy think of this proposal.
Regards,
Ryan Joseph
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