Sven Barth wrote:
On 01.03.2013 23:35, Mark Morgan Lloyd wrote:
Given a procedure definition like
procedure checkLibrariesAndConnect(db: TSQLConnection);
is there a more elegant way of performing type-specific actions than
begin
if db is TPQConnection then begin
end;
if db is TIBConnection then begin
end
end { checkLibrariesAndConnect } ;
i.e. something like case TypeOf(db) ?
No, there is currently no such construct. You could do this though:
=== example begin ===
procedure checkLibrariesAndConnect(db: TSQLConnection);
procedure SetupPQConnection(db: TSQLConnection);
// ...
procedure SetupIBConnection(db: TSQLConnection);
// ...
type
TConnectionInitializer = record
Connection: class of TSQLConnection;
Setup: procedure(db: TSQLConnection) is nested; // needs
{$modeswitch nestedprocvars}
end;
const
ConnectionTypes: array[0..1] of TConnectionInitializer = (
(Connection: TPQConnection; Setup: @SetupPQConnection),
(Connection: TIBConnection; Setup: @SetupIBConnection)
);
var
conn: TConnectionInitializer;
begin
for conn in ConnectionTypes do
if db is conn.Connection then begin
conn.Setup(db);
Break;
end;
end;
=== example end ===
Alternatively if you don't need to check the hierarchy, but can live
with an exact match you can do this:
=== example begin ===
procedure checkLibrariesAndConnect(db: TSQLConnection);
begin
case LowerCase(db.ClassName) of
// Note: .ClassName won't work here
'TPQConnection': ...;
'TIBConnection': ...;
end;
end;
Thanks Sven, noted with interest. case LowerCase(...ClassName) looks
like "the best of a bad job", provided obviously that it's called
infrequently.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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