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