Scopes and names can really be deceiving. A classes in a hierarchy can have members with identical names…
Posted by jpluimers on 2019/11/21
Examples like the one below from [WayBack] Scopes and names can really be deceiving. A root class and a descendant class can both have public fields, properties and methods with the same name… – Lars Fosdal – Google+ used to be part of the “language day” during my 5 day Delphi introductory courses.
Maybe I should find back more of those from the days, brush them up a little, then post them in a repository.
The thread has some nice references to tools that give better warnings and comparisons with other languages.
Anyone wanting to assist with that?
Example code
program PublicScope;
{$APPTYPE CONSOLE}
{$R *.res}
uses
System.SysUtils;
type
TClass1 = class
public
Test: Integer;
constructor Create; virtual;
procedure Dump; virtual;
procedure Oops;
property PropTest:Integer read Test;
end;
TClass2 = class(TClass1)
public
Test:Integer;
constructor Create; override;
procedure Dump; override;
procedure Oops;
property PropTest:Integer read Test;
end;
{ TClass1 }
constructor TClass1.Create;
begin
Test := 1;
end;
procedure TClass1.Dump;
begin
Writeln('TClass1:', Test);
Writeln('TClass1.PropTest:', Test);
end;
procedure TClass1.Oops;
begin
Writeln('TClass1.Oops');
end;
{ TClass2 }
constructor TClass2.Create;
begin
Inherited;
Test := 2;
end;
procedure TClass2.Dump;
begin
Inherited;
Writeln('TClass2.Test:', Test);
Writeln('TClass2.PropTest:', Test);
end;
procedure TClass2.Oops;
begin
Writeln('TClass2.Oops');
end;
procedure Test;
var
c: TClass1;
begin
c := TClass2.Create;
try
Writeln('c: ', c.Test);
c.Dump;
c.Oops;
finally
c.Free;
end;
end;
begin
try
try
Test;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
finally
Write('Press any key: ');
Readln;
end;
end.
Example output
c: 1 TClass1:1 TClass1.PropTest:1 TClass2.Test:2 TClass2.PropTest:2 TClass1.Oops Press any key:
–jeroen
The Wiert Corner - irregular stream of stuff 
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