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functiondelphigenericsparameter-passing
Alexander Krylyk
Alexander Krylyk

Reputation: 41

TFunc<T> - is there any way to pass input parameter modificators?

I need to pass a function as a parameter like this:

procedure SomeProc(AParameter: TFunc<Integer, Integer>);

When I have this function...

function DoSomething(AInput: Integer): Integer;
...
SomeProc(DoSomething);
...

...the Delphi programming code works. But with parameter modifications like const, var, or default values like...

function DoSomething(const AInput: Integer = 0): Integer;

...compiler returns an error of mismatch parameter list.

Is there any way to pass parameter modificators, or avoid this error?

Many thanks for your suggestions.

Upvotes: 3

Views: 964

Answers (3)

FredS
FredS

Reputation: 700

Only if you declare it as a Method reference:

type TDoSomething = reference to function(const AInput: Integer = 0): Integer;

function SomeProc(AParameter: TDoSomething): Integer;
begin
  Result := AParameter;
end;

function CallSomeProc: integer;
begin
  Result := SomeProc(function(const AInput: Integer = 0): Integer begin Result := AInput end);
end;

Upvotes: 5

Uwe Raabe
Uwe Raabe

Reputation: 47714

You can wrap it in an Anonymous Method like this:

SomeProc(function(Arg: Integer): Integer begin Result := DoSomething(Arg) end);

Upvotes: 7

David Heffernan
David Heffernan

Reputation: 612993

Is there any way to pass parameter modificators, or avoid this error?

No. The function you supply to SomeProc must have a signature that matches TFunc<Integer, Integer>.

Upvotes: 4

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