Nullable Types

Language: Oxygene, Platform: Echoes, Category: Language
https://github.com/remobjects/ElementsSamples/tree/master/Oxygene/Echoes/Language/Nullable Types

• NullableTypes
  • References
    • mscorlib
    • System
    • System.Data
    • System.Xml
  • Source Files
    • Program.pas
    • Properties\AssemblyInfo.pas
    • Properties\Resources.Designer.pas
    • Properties\Settings.Designer.pas
  • Other Files
    • Properties\App.ico
    • Properties\Resources.resx
    • Properties\Settings.settings

Program.pas

namespace NullableTypes;

interface

type
  ConsoleApp = class
  public
    class method Main;

  end;

implementation

class method ConsoleApp.Main;

    method UsingColonOperator;
    var
      MyString: String := 'Oxygene';
    begin
       // usual call, lLength = 7;
       var lLength: Int32 := MyString.Length;
       writeLn(lLength);

       MyString := nil;

       // nil value will be converted to 0
       lLength := MyString:Length;

       // lLength2 will be a nullable Int32
       var lLength2 := MyString:Length;
       writeLn(lLength2);
    end;

    method AssigningAndCasting;
    begin
      var n: nullable Int32 := nil;
      var i: Int32 := 10;

      // nil value will be converted to 0
      i := n;

      // following line will throw an invalid cast exception because n is nil
      // i := Int32(n);

      // following line will work fine n = 10;
      i:= 10;
      n := i;
   end;

   method UsingValueOrDefault;
    begin
      var n: nullable Int32; // initialized to nil
      var i: Int32; // initialized to 0

      // will assign 0 if n is nil
      i := valueOrDefault(n);

      // will assign -1 if n is nil
      i := valueOrDefault(n, -1);
      writeLn(i);
    end;

begin
  AssigningAndCasting;
  UsingColonOperator;
  UsingValueOrDefault;
end;


end.