Saving a pointer to specified function in Delphi

Question

Not sure if the tittle is right but what I need to do is to store in some collection a pointer to specified function. I'm doing that pretty much like declaring a variable

SomeFunctionName: string

Of course this type can't be a string, the question is what should it exactly be?

type TGetSomeString = function : string; // read on procedural types in the documentation — OnTheFly
– OnTheFly, Commented Mar 14, 2012 at 13:43
Typically, for methods (procedure or function that belongs to a class) you would use type procedure(args) of object or function(args):resultype of object plus the type declaration. stackoverflow.com/questions/4626614/… — Warren P
– Warren P, Commented Mar 15, 2012 at 13:04

NGLN · Accepted Answer · 2012-03-14 12:01:27Z

6

You would typically use a function pointer variable. For example:

type
  TProcedure = procedure;

procedure MyProc1;
begin
end;

procedure MyProc2;
begin
end;

var
  Proc: TProcedure;

.....
Proc := MyProc1;
Proc();//calls MyProc1
Proc := MyProc2;
Proc();//calls MyProc2

This is the most simple example imaginable. You can specify procedural types that have parameter list, method of object types and so on. Read more in the Procedural Types topic of the language guide.

edited Mar 14, 2012 at 12:01

NGLN

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answered Mar 14, 2012 at 9:39

David Heffernan

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2 Comments

David Heffernan Over a year ago

@TLama Yes I've seen it from time to time. I have reported it: meta.stackexchange.com/questions/125587/…

Ville Krumlinde Over a year ago

@JacekKwiecień See the section named "Method Pointers" in the page that David refers to.

Community · Accepted Answer · 2017-05-23 11:45:39Z

1

You are actually not storing procedure / function but storing method.

So you should use TMethod Instead. A TMethod has a object pointer and a procedure pointer.

You can see more detail in another post : Save and restore event handlers

edit : It seems the question has been edit back to original after showing some Storing TControl.onClick event request.....

edited May 23, 2017 at 11:45

CommunityBot

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answered Mar 14, 2012 at 12:11

Justmade

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