Methods to convert a string TValue to the desired simple type (Like Integer, Float, DateTime);

[dmitrybv 3]

Are there methods in the TValue class or in Rtti to convert a string to the desired simple type (Like Integer, Float, DateTime)?

 

TValue has a method that converts a simple value to a string - TValue.ToString, but there is no reverse method TValue.FromString.

I tried using StrValue.Cast<Integer>();
but this method throws 'Invalid class typecast' exception.

 

procedure TFormSimpleDraw2.Button3Click(Sender: TObject);
var
  StrValue: TValue;
  IntValue: TValue;
  Str: String;
begin
  IntValue := 10;
  StrValue := IntValue.ToString();
//  IntValue := TValue.FromString(Str);
  IntValue := StrValue.Cast<Integer>();
end;

 

[Der schöne Günther 316]

TValue is designed to hold any type, not just "simple" ones. There is no way to marshal a string representation like "(record)" or "(interface @ 02549BD0)" back into what they once were.

 

Maybe what you are looking for is a mechanism to serialize any record/object in memory into a string (or raw bytes), store them, and later de-serialize them?

Edited August 20 by Der schöne Günther

[Stefan Glienke 2019]

Convert<T> from TValueHelper in Spring. See https://bitbucket.org/sglienke/spring4d/src/2.0.1/Source/Base/Spring.pas#lines-651