Nested types

New features since Delphi 7 > Generics > Nested types

A nested type within a generic is itself a generic.

type

  TFoo<T> = class

  type

    TBar = class

      X: Integer;

      // ...

    end;

  end;

  // ...

  TBaz = class

  type

    TQux<T> = class

      X: Integer;

      // ...

    end;

    // ...

  end;

var

   n: TFoo<Double>.TBar;

->

private class TFoo<T> : TObject

{

  public class TBar : TObject

  {

    public int X;

      // ...

    public TBar() {}

  };  

  public TFoo() {}

};

  // ...

private class TBaz : TObject

{

  public class TQux<T> : TObject

  {

    public int X;

      // ...

    public TQux() {}

  };  

    // ...

  public TBaz() {}

};

private static TFoo<double>.TBar N = null;

A generic can also be declared within a regular class as a nested type:

type

   TOuter = class

   type

     TData<T> = class

       FFoo1: TFoo<Integer>;         // declared with closed constructed type

       FFoo2: TFoo<T>;               // declared with open constructed type

       FFooBar1: TFoo<Integer>.TBar; // declared with closed constructed type

       FFooBar2: TFoo<T>.TBar;       // declared with open constructed type

       FBazQux1: TBaz.TQux<Integer>; // declared with closed constructed type

       FBazQux2: TBaz.TQux<T>;       // declared with open constructed type

       //...

     end;

   var

     FIntegerData: TData<Integer>;

     FStringData: TData<String>;

   end;

->

public class TOuter : TObject

{

  public class TData<T> : TObject

  {

    public TFoo<int> FFoo1;         // declared with closed constructed type

    public TFoo<T> FFoo2;               // declared with open constructed type

    public TFoo<int>.TBar FFooBar1; // declared with closed constructed type

    public TFoo<T>.TBar FFooBar2;       // declared with open constructed type

    public TBaz.TQux<int> FBazQux1; // declared with closed constructed type

    public TBaz.TQux<T> FBazQux2;       // declared with open constructed type

       //...

    public TData() {}

  };  

  public TData<int> FIntegerData;

  public TData<string> FStringData;

  public TOuter() {}

};

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