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How to assign an interface variable to a variable of type Rtti.TValue

I am giving delphi2010 a trial at the moment and found the TValue type of the Rtti module. TValue has some very cool features, but I can't seem to find a way to assign the interface.

I will try the following

program Project1;
uses
  Classes, SysUtils, Rtti;
var
   list : IInterfaceList;
   value : TValue;
begin
  // all these assignments works
  value := 1;
  value := 'Hello';
  value := TObject.Create;

  // but nothing of these assignments works
  list := TInterfaceList.Create;
  value := list; // [DCC Fehler] Project1.dpr(15): E2010 incompatible types: 'TValue' and 'IInterfaceList'
  value.From[list]; // [DCC Fehler] Project1.dpr(16): E2531 Method 'From' requires explicit typarguments
  value.From<IInterfaceList>[list]; // [DCC Fehler] Project1.dpr(17): E2035 Not enough parameters
end.

I cannot find any further information. Not on the delphi help system, not on the web. What am I doing wrong?

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2 answers


Your last try is your closest. TValue.From is a class function that creates TValue from a parameter. You probably put square brackets in there because, as CodeInsight showed, right? This is actually a glitch in CodeInsight; it does this for generic functions, where you should use parentheses instead. The correct syntax is as follows:



Value := TValue.From<IInterfaceList>(list);
+6


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This is the working version of the program:



program Project1;
uses
  Classes, SysUtils, Rtti;
var
   list : IInterfaceList;
   value : TValue;
begin
  // all these assignments works
  value := 1;
  value := 'Hello';
  value := TObject.Create;

  // but nothing of these assignments works
  list := TInterfaceList.Create;
  value := TValue.From(list);
end.
+7


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