How to get a method param name array/list in Delphi?

Question

Is there any way to get the names of the parameters of a given method of a class/object in an array/delimited string in Delphi 7? Somehow like this:

var
  s : string;
  aSL : TStringList;
begin
  ...
  // using rtti calls in TMethodUtility.collectParamNames
  s := TMethodUtility.collectParamNames( TStringList.addObject );
  // or
  TMethodUtility.collectParamNames( TStringList.addObject, aSL );
  ...
end;

Thanks in advance!

There is no AddItem() method in TString/List. There is Add() and AddObject() instead. — Remy Lebeau

Remy Lebeau Remy Lebeau · Accepted Answer · 2016-07-21T18:38:41

It is technically possible (otherwise the IDE's Form Designer could not generate code for component event handlers at design-time), however, there are important caveats that will hinder your goal (and make the particular example in your question impossible to resolve):

the necessary RTTI is only generated for properties that are declared as published (such as component events). RTTI is not generated for methods themselves (even published ones), or for properties that are not published.
TObject has a public MethodAddress() method for getting the memory address of a published method (the DFM streaming system uses this when hooking up event handlers), however you cannot get the necessary RTTI from a method pointer alone.

IF you can match a given method pointer to the value of a published event, then you can extract the parameter names from the event's RTTI. Obtain a TypInfo.PPropInfo pointer for the event using the TypInfo.GetPropInfo() function, then pass its PropType field value to the TypInfo.GetTypeData() function to get a TypInfo.PTypeData pointer, and then you can iterate through its ParamList field (which is an array of records containing ParamName and TypeName fields).

See the following blog article on this topic for more details:

Getting the parameters of published methods.

For what you are attempting, a general-purpose solution would require Extended RTTI that was introduced in Delphi 2010 and thus is not available in Delphi 7. Extended RTTI is not limited to published items, and is much more detailed than what the old-style RTTI provides.

How to get a method param name array/list in Delphi?

1 Answers