Re: [fpc-pascal] Iterating over elements from GetDynArrayProp
On Sat, 15 Oct 2022, Hairy Pixels via fpc-pascal wrote: How can I iterate over the pointer that is returned from GetDynArrayProp? I tried to cast it as a dynamic array of the element type but calling Length() on the returned value gave garbled data. For example with a property of the type “array of TObject": type TObjectArray = array of TObject; PObjectArray = ^TObjectArray; var ObjectArray: PObjectArray; begin ObjectArray := PObjectArray(GetDynArrayProp(AObject, PropertyInfo)); as far as I kbow, this should be ObjectArray := TObjectArray(GetDynArrayProp(AObject, PropertyInfo)); i.e. you get the actual array as a result. Michael.___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Iterating over elements from GetDynArrayProp
> On Oct 15, 2022, at 3:03 PM, Michael Van Canneyt > wrote: > > as far as I kbow, this should be > ObjectArray := TObjectArray(GetDynArrayProp(AObject, PropertyInfo)); > i.e. you get the actual array as a result. > You’re right, I didn’t need that pointer cast. I’m still curious though why that didn’t work. Shouldn’t the pointer still just point to the dynamic array address and basically do nothing? Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Iterating over elements from GetDynArrayProp
On Sat, 15 Oct 2022, Hairy Pixels wrote: On Oct 15, 2022, at 3:03 PM, Michael Van Canneyt wrote: as far as I kbow, this should be ObjectArray := TObjectArray(GetDynArrayProp(AObject, PropertyInfo)); i.e. you get the actual array as a result. You’re right, I didn’t need that pointer cast. I’m still curious though why that didn’t work. Shouldn’t the pointer still just point to the dynamic array address and basically do nothing? No, it's perfectly logical what is happening. You can't cast a type (TA) to a pointer to that type (^PTA) and expect the compiler to automagically forget the extra dereference when you dereference it... Michael.___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] Open array compatibility
Another question I just ran in to. Why isn’t "array of TMyClass” compatible
with “array of TObject” open array? TMyClass is a descendant of TObject and
dynamic arrays are compatible with open arrays right?
==
type
TMyClass = class
end;
procedure MyProcedure(values: array of TObject);
begin
end;
var
myArray: array of TMyClass;
begin
MyProcedure(myArray); // error: Incompatible type for arg no. 1: Got
"{Dynamic} Array Of TMyClass", expected "{Open} Array Of TObject"
Regards,
Ryan Joseph
___
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Re: [fpc-pascal] Open array compatibility
On Sat, 15 Oct 2022, Hairy Pixels via fpc-pascal wrote:
Another question I just ran in to. Why isn’t "array of TMyClass” compatible
with “array of TObject” open array? TMyClass is a descendant of TObject and dynamic
arrays are compatible with open arrays right?
==
type
TMyClass = class
end;
procedure MyProcedure(values: array of TObject);
begin
end;
var
myArray: array of TMyClass;
begin
MyProcedure(myArray); // error: Incompatible type for arg no. 1: Got "{Dynamic} Array Of
TMyClass", expected "{Open} Array Of TObject"
Rougly said:
Arrays are considered equal if the element type is equal.
And equal does not mean 'inherits from'.
One reason we do not allow descendents is that if you have a var array, the
returned value may contain classes of a type that the caller does not expect.
(This is the same reason why (var value: TObject) requires an exact match in
type)
But a case could be made to allow it in case the parameter is passed by value.
You can force it with a typecast:
Type
TObjectArray = Array of Object;
var
myArray: array of TMyClass;
begin
MyProcedure(TObjectArray(myArray));
end.
But then you're on you own, as you are deliberately bypassing the compiler's
typechecking (as is the case with all typecasts...).
Michael.___
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Re: [fpc-pascal] Open array compatibility
> On Oct 15, 2022, at 3:58 PM, Michael Van Canneyt > wrote: > > One reason we do not allow descendents is that if you have a var array, the > returned value may contain classes of a type that the caller does not expect. > (This is the same reason why (var value: TObject) requires an exact match in > type) > Ah ok, I guess there would need to be an “array of class” like it used with generic param constraints i.e. . I’m trying to do some tricks with overloading which is why I ask. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] Exploring block statements with CodeTools not working
I’m trying to look at the code in a the begin..end section of this sample program but for some reason when it gets to the BeginBlock node child count is always 0 (other nodes are as expected though). I’m calling Explore correctly I think so what could the problem be? Here is the little test program I’m using along with a snippet which explores the code and walks the tree. Btw, I understand this question is basically for Mattias but I don’t know where else to post. Does Mattias prefer I post in one of these forums https://forum.lazarus.freepascal.org or maybe email privately with code tools questions? program test; var A: Integer; begin A := 1; end. CodeToolBoss.Explore(Code, Tool, true); Node := tool.Tree.Root; while Node <> nil do begin writeln(Node.DescAsString, ‘ -> ’, Node.ChildCount); Node := Node.Next; end; Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Exploring block statements with CodeTools not working
Am 16.10.2022 um 04:19 schrieb Hairy Pixels via fpc-pascal: Btw, I understand this question is basically for Mattias but I don’t know where else to post. Does Mattias prefer I post in one of these forums https://forum.lazarus.freepascal.org or maybe email privately with code tools questions? Though I am not Mattias and cannot comment on his preferences: CodeTools are part of the Lazarus project, hence the question belongs to the Lazarus mailing list https://lists.lazarus-ide.org/listinfo/lazarus or one of the IDE categories in the forum. Ondrej ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
