tmemorystream: no member set size / get memory

[Selfmade.exe]

Hello everyone,

Data:= TMemoryStream.Create; // this is ok
Data.SetSize( 8 ); // this is NOT ok
s:= data.memory; // this is NOT ok


I get  Error: identifier idents no member "SetSize" & Error: identifier idents no member "memory"

[Selfmade.exe]

Never mind fellas, I found it, my bad.

It was

var Data: TStream;
and
Data:=TMemoryStream.Create

The correct is

var Data: TMemoryStream;
and
Data:=TMemoryStream.Create

[Thaddy]

For completeness, you were on the right track.
It is OK to declare as Tstream, but then you need to use it like this:

Code: Pascal  [Select][+][-]

1. {$mode objfpc}
2. uses classes;
3. // access to memorystream specific methods and properties from TStream;
4. var
5.   data:Tstream;
6. begin
7.   data := TmemoryStream.Create;
8.   // either soft cast
9.   (data as TmemoryStream).SetSize(8);
10.   // or hard cast
11.   TMemoryStream(Data).SetSize(8);
12.   Data.free;
13. end.

That way you can still assign the data stream to any other Tstream descendant.
Methods and properties that are shared with the ancestor class (read/write) do not need a cast.

[Selfmade.exe]

Nice one @Thaddy! I just learned something new from your post! I hope that this thread gets the attention of anyone that might be in a similar situation.

[Remy Lebeau]

Code: Pascal  [Select][+][-]

1. // either soft cast
2. (data as TmemoryStream).SetSize(8);
3. // or hard cast
4. TMemoryStream(Data).SetSize(8);

You don't need a cast at all.  Just use the public TStream.Size property instead:

Code: Pascal  [Select][+][-]

1. Data.Size := 8;

[Thaddy]

[You don't need a cast at all.  Just use the public TStream.Size property instead:

Was merely meant as example in case it is a a member of TMemoryStream as opposed to TStream.
Furthermore, not every stream has a size. https://www.freepascal.org/docs-html/rtl/classes/tstream.size.html
(As such it is actually a theoretically flawed implementation, but it is is Delphi legacy)