Marco, it doesn't work that way.
Type helpers simply allow you to extend an existing type with new methods
and/or properties. When you declare a type helper you extend all instances
of said type given that:
A) You 'use' the unit declaring the type helper in some other unit.
B) No other unit you're using also defines a type helper for that same
type. Only one type helper per type allowed.
As to what they are useful for, consider the following:
type
// IShellLink is define by Microsoft
IShellLinkHelper = record helper for IShellLink
public
procedure Save(const Target, Description, Link: string);
end;
procedure IShellLinkHelper.Save(const Target, Description, Link: string);
var
P: IPersistsFile;
begin
SetPath(Target);
SetDescription(Description);
if Self is IPersistsFile then
begin
P := Self as IPersistsFile;
P.Save(Link, True);
end;
end;
...
CoCreateInstance(CLSID_ShellLink, nil, CLSCTX_INPROC_SERVER, IShellLink,
Link);
Link.Save('C:\Program Files\Google\chrome.exe', 'Web Browser',
C:\Users\me\Desktop\The Internet.lnk')
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