Language and Compiler Features Since Delphi 7

New Delphi language features since Delphi 7

By: Nick Hodges

Abstract: See many of the major new language features in Delphi released after the Delphi 7 version

Language and Compiler Features Since Delphi 7
Inlining	Routines can now be marked with the inline directive.  This tells the compiler that, instead of actually calling the routine, it should emit code that includes the routine at the call site.
Operator Overloading	Delphi allows certain functions, or operators, to be overloaded within record declarations TMyClass = class class operator Add(a, b: TMyClass): TMyClass; // Addition of two operands of type TMyClass class operator Subtract(a, b: TMyClass): TMyclass; // Subtraction of type TMyClass class operator Implicit(a: Integer): TMyClass; // Implicit conversion of an Integer to type TMyClass class operator Implicit(a: TMyClass): Integer; // Implicit conversion of TMyClass to Integer class operator Explicit(a: Double): TMyClass; // Explicit conversion of a Double to TMyClass end; // Example implementation of Add class operator TMyClass.Add(a, b: TMyClass): TMyClass; begin ... end; var x, y: TMyClassbegin x := 12; // Implicit conversion from an Integer y := x + x; // Calls TMyClass.Add(a, b: TMyClass): TMyClass b := b + 100; // Calls TMyClass.Add(b, TMyClass.Implicit(100)) end;
Class Helpers	A class helper is a type that - when associated with another class - introduces additional method names and properties which may be used in the context of the associated class (or its descendants). Class helpers are a way to extend a class without using inheritance. A class helper simply introduces a wider scope for the compiler to use when resolving identifiers. When you declare a class helper, you state the helper name, and the name of the class you are going to extend with the helper. You can use the class helper any place where you can legally use the extended class. The compiler's resolution scope then becomes the original class, plus the class helper. Class helpers provide a way to extend a class, but they should not be viewed as a design tool to be used when developing new code. They should be used solely for their intended purpose, which is language and platform RTL binding. type TMyClass = class procedure MyProc; function MyFunc: Integer; end; ... procedure TMyClass.MyProc; var X: Integer; begin X := MyFunc; end; function TMyClass.MyFunc: Integer; begin ... end; ... type TMyClassHelper = class helper for TMyClass procedure HelloWorld; function MyFunc: Integer; end; ... procedure TMyClassHelper.HelloWorld; begin WriteLn(Self.ClassName); // Self refers to TMyClass type, not TMyClassHelper end; function TMyClassHelper.MyFunc: Integer; begin ... end; ... var X: TMyClass; begin X := TMyClass.Create; X.MyProc; // Calls TMyClass.MyProc X.HelloWorld; // Calls TMyClassHelper.HelloWorld X.MyFunc; // Calls TMyClassHelper.MyFunc end;
strict private	The private keyword actually creates a " friendship" relationship between classes in the same unit.  The strict private declaration creates a true private field, not viewable by any other class, not even classes in the same unit.
strict protected	Similar to the strict private declaration, strict protectedcreates a true protected member, visible only to the declaring class and its descendents.
Records with Methods	In addition to fields, records now may have properties and methods (including constructors), class properties, class methods, class fields, and nested types.  type TMyRecord = record type TInnerColorType = Integer; var Red: Integer; class var Blue: Integer; procedure printRed(); constructor Create(val: Integer); property RedProperty: TInnerColorType read Red write Red; class property BlueProp: TInnerColorType read Blue write Blue; end; constructor TMyRecord.Create(val: Integer); begin Red := val; end; procedure TMyRecord.printRed; begin writeln('Red: ', Red); end;
class abstract	Classes, and not just methods, can be declared as abstract. type TAbstractClass = class abstract procedure SomeProcedure; end;
class sealed	Classes marked as sealed cannot be inherited from. type TAbstractClass = class sealed procedure SomeProcedure; end;
class const	Classes can now have class constants -- a constant value associated with the class itself and not an instance of the class. type TClassWithConstant = class public const SomeConst = 'This is a class constant'; end; procedure TForm1.FormCreate(Sender: TObject); begin ShowMessage(TClassWithConstant.SomeConst); end;
class type	A class can now contain a type declaration that is usable only within that class. type TClassWithClassType = class private type TRecordWithinAClass = record SomeField: string; end; public class var RecordWithinAClass: TRecordWithinAClass; end; ... procedure TForm1.FormCreate(Sender: TObject); begin TClassWithClassType.RecordWithinAClass.SomeField := 'This is a field of a class type declaration'; ShowMessage(TClassWithClassType.RecordWithinAClass.SomeField); end;
class var	A class can also have a class variable, applicable only to the class and not an instance of the class. See "class type" for an example.
class property	A class can have a class property, which is a property that applies only to the class reference and not to an instance of a class.  The accessors for the class property must be either class methods or class variables. See the example in "static class methods" below.
nested classes	Type declarations can be nested within class declarations. They present a way to keep conceptually related types together, and to avoid name collisions. type TOuterClass = class strict private MyField: Integer; public type TInnerClass = class public MyInnerField: Integer; procedure InnerProc; end; procedure OuterProc; end; procedure TOuterClass.TInnerClass.InnerProc; begin ... end;
final methods	A virtual method that you override can now be marked final, preventing derived classes from overriding that method. TAbstractClass = classabstract public procedure Bar; virtual; end; TSealedClass = classsealed(TAbstractClass) public procedure Bar; override; end; TFinalMethodClass = class(TAbstractClass) public procedure Bar; override; final; end;
sealed methods	Classes marked as sealed cannot be descended from. See the example in 'final methods'.
static class methods	Classes can have static class methods -- i.e. methods that can be called from a class type. Class static methods can be accessed without an object reference. Unlike ordinary class methods, class static methods have no Self parameter at all. They also cannot access any instance members. (They still have access to class fields, class properties, and class methods.) Also unlike class methods, class static methods cannot be declared virtual. type TMyClass = class strict private class var FX: Integer; strict protected // Note: accessors for class properties must be declared class static. class function GetX: Integer; static; class procedure SetX(val: Integer); static; public class property X: Integer read GetX write SetX; class procedure StatProc(s: String); static; end; TMyClass.X := 17; TMyClass.StatProc('Hello');
for-in loop	Delphi 2007 for Win32 supports for-element-in-collection style iteration over containers. The following container iteration patterns are recognized by the compiler: for Element in ArrayExpr do Stmt; for Element in StringExpr do Stmt; for Element in SetExpr do Stmt; for Element in CollectionExpr do Stmt;