I was thinking about my patch for default properties and how invasive the
changes are into the compiler and heavy handed the approach is. I’m not even
sure the compiler team would accept it like it is since it has such potential
for overreach and having strange unpredictable effects.
In my opinion C++ has a more reasonable approach which does 95% of the things
we actually need for the use cases (i.e. nullable types/ARC-like classes, like
shared_ptr in C++). Their approach is to allow overriding the “postfix"
operator (-> in C++ but “.” for classes in FPC) which is then used in
conjunction with various other operator overloads (like := and =).
I think this solution is better because:
1) The changes in the compiler sources are maybe 10% of what they need to be
with default properties.
2) The user can better manage access to the underlying class instead of
hoisting up the entire namespace up for all possible circumstances. This
approach gives the user much greater control overall.
3) The effects are very predictable, that is, you know it only affects the
record when you use “.”. Default properties need to have wide-reaching effects
in a multitude of different syntaxes.
4) It has the support of the C++ team and years of real world usage
(std::shared_ptr etc…).
Does that make sense? I’d like to scratch the idea of default properties and do
this instead if it was permitted.
========================
type
TAuto<T> = record
m_obj: T;
// … other management operators …
class operator postfix: T;
end;
class operator TAuto.postfix: T;
begin
result := m_obj;
end;
var
a: TAuto<TObject>;
begin
writeln(a.ClassName); // a.m_obj.ClassName
Regards,
Ryan Joseph
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