delphi xe3的helper语法 good

在C#中有一个很有用的helper保留字,它可以让我们对已有的类添加额外功能,当时就在想delphi有这个保留字就好了,这样许多控件就不需要继承重写了.后来delphi 果然有了这个语法,到delphixe3,这个保留字就很强大了,不但class、record类型可用,现在连pascal基本类型也能使用了。实际上delphixe3 的string类型就是这样使用的。具体可查看System.SysUtils源代码。 那么对整数integer int64等类型可用吗？答案是肯定。

ThelperUInt64 = record helper for UInt64
  private
  public
    function ToString: string;
    function ToHex(Digits: integer): string;
  end;
这样，就可以在程序中使用如下语法形式了，
var
  ui64:uint64;
begin
  ui64:=34567;
  showmessage(ui64.ToString);//'34567'
end;
其实这不是最有用的,最有用是弥补祖先类控件的不足,比如

ThelperEdit = record helper for Tedit
  public
    function Asinteger:integer;
    function AsDateTime: TDateTime;
    function Setkeycontrol(var rkey: Char; RightSet: TSysCharSet);
  end;
这样所有包含和继承于Tedit的控件 就都可以使用 以上函数了,而不必一个个重载了.
------  附System.SysUtils 的TStringHelper
 TStringHelper = record helper for string
  private
    function GetChars(Index: Integer): Char; inline;
    function GetLength: Integer; inline;
    class function CharInArray(const C: Char; const InArray: array of Char): Boolean; static;
    function IndexOfAny(const Values: array of string; var Index: Integer): Integer; overload;
  public
    const Empty = '';
    // Methods
    class function Create(C: Char; Count: Integer): string; overload; inline; static;
    class function Create(const Value: array of Char; StartIndex: Integer; Length: Integer): string; overload; static;
    class function Create(const Value: array of Char): string; overload; static;
    class function Compare(const StrA: string; const StrB: string): Integer; overload; static;
    class function Compare(const StrA: string; const StrB: string; IgnoreCase: Boolean): Integer; overload; static;
    class function Compare(const StrA: string; IndexA: Integer; const StrB: string; IndexB: Integer; Length: Integer): Integer; overload; static;
    class function Compare(const StrA: string; IndexA: Integer; const StrB: string; IndexB: Integer; Length: Integer; IgnoreCase: Boolean): Integer; overload; static;
    class function CompareOrdinal(const strA: string; const strB: string): Integer; overload; static;
    class function CompareOrdinal(const strA: string; indexA: Integer; const strB: string; indexB: Integer; length: Integer): Integer; overload; static;
    function CompareTo(const strB: string): Integer;
    function Contains(const Value: string): Boolean;
    class function Copy(const Str: string): string; inline; static;
    procedure CopyTo(SourceIndex: Integer; var destination: array of Char; DestinationIndex: Integer; Count: Integer);
    class function EndsText(const ASubText, AText: string): Boolean; static;
    function EndsWith(const Value: string): Boolean; overload;
    function EndsWith(const Value: string; IgnoreCase: Boolean): Boolean; overload;
    function Equals(const Value: string): Boolean; overload;
    class function Equals(const a: string; const b: string): Boolean; overload; static;
    class function Format(const Format: string; const args: array of const): string; overload; static;
    function GetHashCode: Integer;
    function IndexOf(value: Char): Integer; overload; inline;
    function IndexOf(const Value: string): Integer; overload; inline;
    function IndexOf(Value: Char; StartIndex: Integer): Integer; overload;
    function IndexOf(const Value: string; StartIndex: Integer): Integer; overload;
    function IndexOf(Value: Char; StartIndex: Integer; Count: Integer): Integer; overload;
    function IndexOf(const Value: string; StartIndex: Integer; Count: Integer): Integer; overload;
    function IndexOfAny(const AnyOf: array of Char): Integer; overload;
    function IndexOfAny(const AnyOf: array of Char; StartIndex: Integer): Integer; overload;
    function IndexOfAny(const AnyOf: array of Char; StartIndex: Integer; Count: Integer): Integer; overload;
    function Insert(StartIndex: Integer; const Value: string): string;
//    function IsNormalized: Boolean; overload;
//    function IsNormalized(NormalizationForm: TNormalizationForm): Boolean; overload;
    function IsDelimiter(const Delimiters: string; Index: Integer): Boolean;
    function IsEmpty: Boolean;
    class function IsNullOrEmpty(const Value: string): Boolean; static;
    class function IsNullOrWhiteSpace(const Value: string): Boolean; static;
    class function Join(const Separator: string; const values: array of const): string; overload; static;
    class function Join(const Separator: string; const Values: array of string): string; overload; static;
//    class function Join(Separator: string; const values: IEnumerable): string; overload; static;
    class function Join(const Separator: string; const Values: IEnumerable): string; overload; static;
    class function Join(const Separator: string; const value: array of string; StartIndex: Integer; Count: Integer): string; overload; static;
    function LastDelimiter(const Delims: string): Integer;
    function LastIndexOf(Value: Char): Integer; overload;
    function LastIndexOf(const Value: string): Integer; overload;
    function LastIndexOf(Value: Char; StartIndex: Integer): Integer; overload;
    function LastIndexOf(const Value: string; StartIndex: Integer): Integer; overload;
    function LastIndexOf(Value: Char; StartIndex: Integer; Count: Integer): Integer; overload;
    function LastIndexOf(const Value: string; StartIndex: Integer; Count: Integer): Integer; overload;
    function LastIndexOfAny(const AnyOf: array of Char): Integer; overload;
    function LastIndexOfAny(const AnyOf: array of Char; StartIndex: Integer): Integer; overload;
    function LastIndexOfAny(const AnyOf: array of Char; StartIndex: Integer; Count: Integer): Integer; overload;
    function PadLeft(TotalWidth: Integer): string; overload; inline;
    function PadLeft(TotalWidth: Integer; PaddingChar: Char): string; overload; inline;
    function PadRight(TotalWidth: Integer): string; overload; inline;
    function PadRight(TotalWidth: Integer; PaddingChar: Char): string; overload; inline;
    function Remove(StartIndex: Integer): string; overload; inline;
    function Remove(StartIndex: Integer; Count: Integer): string; overload; inline;
    function Replace(OldChar: Char; NewChar: Char): string; overload;
    function Replace(OldChar: Char; NewChar: Char; ReplaceFlags: TReplaceFlags): string; overload;
    function Replace(const OldValue: string; const NewValue: string): string; overload;
    function Replace(const OldValue: string; const NewValue: string; ReplaceFlags: TReplaceFlags): string; overload;
    function Split(const Separator: array of Char): TArray; overload;
    function Split(const Separator: array of Char; Count: Integer): TArray; overload;
    function Split(const Separator: array of Char; Options: TStringSplitOptions): TArray; overload;
    function Split(const Separator: array of string; Options: TStringSplitOptions): TArray; overload;
    function Split(const Separator: array of Char; Count: Integer; Options: TStringSplitOptions): TArray; overload;
    function Split(const Separator: array of string; Count: Integer; Options: TStringSplitOptions): TArray; overload;
    function StartsWith(const Value: string): Boolean; overload;
    function StartsWith(const Value: string; IgnoreCase: Boolean): Boolean; overload;
    function Substring(StartIndex: Integer): string; overload;
    function Substring(StartIndex: Integer; Length: Integer): string; overload;
    function ToCharArray: TArray; overload;
    function ToCharArray(StartIndex: Integer; Length: Integer): TArray; overload;
    function ToLower: string;
    function ToLowerInvariant: string;
    function ToUpper: string;
    function ToUpperInvariant: string;
    function Trim: string; overload;
    function Trim(const TrimChars: array of Char): string; overload;
    function TrimEnd(const TrimChars: array of Char): string;
    function TrimStart(const TrimChars: array of Char): string;
    property Chars[Index: Integer]: Char read GetChars;
    property Length: Integer read GetLength;
  end;

http://blog.sina.com.cn/s/blog_53866d750101697b.html