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今天简单介绍一下 delphi 中record 的类操作符重载使用,就是如何 实现 record 之间的简单操作。

关于类操作符重载 ,大家可以看 官方的文档。

 

Delphi allows certain functions, or "operators", to be overloaded within record declarations. The name of the operator function maps to a symbolic representation in source code. For example, the Add operator maps to the + symbol.

The compiler generates a call to the appropriate overload, matching the context (that is, the return type, and type of parameters used in the call), to the signature of the operator function.

The following table shows the Delphi operators that can be overloaded:

OperatorCategoryDeclaration SignatureSymbol Mapping

Implicit

Conversion

Implicit(a : type) : resultType;

implicit typecast

Explicit

Conversion

Explicit(a: type) : resultType;

explicit typecast

Negative

Unary

Negative(a: type) : resultType;

-

Positive

Unary

Positive(a: type): resultType;

+

Inc

Unary

Inc(a: type) : resultType;

Inc

Dec

Unary

Dec(a: type): resultType

Dec

LogicalNot

Unary

LogicalNot(a: type): resultType;

not

Trunc

Unary

Trunc(a: type): resultType;

Trunc

Round

Unary

Round(a: type): resultType;

Round

In

Set

In(a: type; b: type) : Boolean;

in

Equal

Comparison

Equal(a: type; b: type) : Boolean;

=

NotEqual

Comparison

NotEqual(a: type; b: type): Boolean;

<>

GreaterThan

Comparison

GreaterThan(a: type; b: type) Boolean;

>

GreaterThanOrEqual

Comparison

GreaterThanOrEqual(a: type; b: type): Boolean;

>=

LessThan

Comparison

LessThan(a: type; b: type): Boolean;

<

LessThanOrEqual

Comparison

LessThanOrEqual(a: type; b: type): Boolean;

<=

Add

Binary

Add(a: type; b: type): resultType;

+

Subtract

Binary

Subtract(a: type; b: type) : resultType;

-

Multiply

Binary

Multiply(a: type; b: type) : resultType;

*

Divide

Binary

Divide(a: type; b: type) : resultType;

/

IntDivide

Binary

IntDivide(a: type; b: type): resultType;

div

Modulus

Binary

Modulus(a: type; b: type): resultType;

mod

LeftShift

Binary

LeftShift(a: type; b: type): resultType;

shl

RightShift

Binary

RightShift(a: type; b: type): resultType;

shr

LogicalAnd

Binary

LogicalAnd(a: type; b: type): resultType;

and

LogicalOr

Binary

LogicalOr(a: type; b: type): resultType;

or

LogicalXor

Binary

LogicalXor(a: type; b: type): resultType;

xor

BitwiseAnd

Binary

BitwiseAnd(a: type; b: type): resultType;

and

BitwiseOr

Binary

BitwiseOr(a: type; b: type): resultType;

or

BitwiseXor

Binary

BitwiseXor(a: type; b: type): resultType;

xor


No operators other than those listed in the table may be defined on a class or record.

 

以下是通过实例来演示

TXalionRec=record
   ival:integer;
   dval:Tdatetime;
   constructor create;
   destructor Destroy;

    class operator Assign(var Dest:TXalionRec;const Src:TXalionRec); // 赋值

    class operator NotEqual(ALeft,ARight:TXalionRec):boolean;  // 不等于
    class operator Equal(ALeft,ARight:TXalionRec):boolean;  //等于
    class operator GreaterThan(ALeft,ARight:TXalionRec):boolean; // 大于
    class operator GreaterThanOrEqual(ALeft,ARight:TXalionRec):boolean;  //大于等于
    class operator LessThan(ALeft,ARight:TXalionRec):boolean; // 小于
    class operator LessThanOrEqual(ALeft,ARight:TXalionRec):boolean; //小于等于
    class operator Inc(AValue:TXalionRec):TXalionRec;    // 递增
    class operator Dec(AValue:TXalionRec):TXalionRec;     // 递减

    class operator Add(AValue1:TXalionRec; AValue2:integer):TXalionRec;    // 加整数
    class operator Add(AValue1:TXalionRec; AValue2:TDateTime):TXalionRec;    //加时间
    class operator Add(AValue1:TXalionRec; AValue2:TXalionRec):TXalionRec;    // 直接加


    class operator Implicit(AValue:TDateTime):TXalionRec;  //显式等于日期
    class operator Implicit(AValue:integer):TXalionRec;    //显式等于整数

    class operator Implicit(AValue:TXalionRec):TDateTime; //显式赋值日期
    class operator Implicit(AValue:TXalionRec):integer; //显式赋值整数
end;


var
  Form2: TForm2;

implementation

{$R *.dfm}

{ TXalionRec }

class operator TXalionRec.Assign(var Dest:TXalionRec;const Src:TXalionRec);
 begin
     dest.ival:=src.ival;
     dest.dval:=src.dval;
 end;

class operator TXalionRec.Add(AValue1: TXalionRec;
  AValue2: TDateTime): TXalionRec;
begin
result:=  AValue1;
result.dval:=result.dval+avalue2;
end;

class operator TXalionRec.Add(AValue1: TXalionRec;
  AValue2: integer): TXalionRec;
begin
    result:=  AValue1;
     result.ival:=result.ival+avalue2;
end;

class operator TXalionRec.Add(AValue1:TXalionRec; AValue2:TXalionRec):TXalionRec;
begin
        result.ival :=avalue1.ival+avalue2.ival;
        result.dval:= avalue1.dval+avalue2.dval;
end;

constructor TXalionRec.create;
begin
    ival:=0;
    dval:=now;
end;

class operator TXalionRec.Dec(AValue: TXalionRec): TXalionRec;
begin
   result:=Avalue;
    dec(result.ival);
end;

destructor TXalionRec.Destroy;
begin
    exit;
end;

class operator TXalionRec.Equal(ALeft, ARight: TXalionRec): boolean;
begin
  result:=False;
    if Aleft.ival=Aright.ival then
    begin
        result:=True;
    end;

end;

class operator TXalionRec.GreaterThan(ALeft, ARight: TXalionRec): boolean;
begin
      result:=False;
       if Aleft.ival>Aright.ival then
          result:=True;
end;

class operator TXalionRec.GreaterThanOrEqual(ALeft,
  ARight: TXalionRec): boolean;
begin
    result:=False;
       if Aleft.ival>=Aright.ival then
          result:=True;
end;

class operator TXalionRec.Implicit(AValue: integer): TXalionRec;
begin
     result.ival:=Avalue;
end;

class operator TXalionRec.Implicit(AValue: TDateTime): TXalionRec;
begin
     result.dval:=Avalue;
end;

class operator TXalionRec.Implicit(AValue: TXalionRec): integer;
begin
    result:=Avalue.ival;
end;

class operator TXalionRec.Implicit(AValue: TXalionRec): TDateTime;
begin
      result:=Avalue.dval;
end;

class operator TXalionRec.Inc(AValue: TXalionRec): TXalionRec;
begin
    result:=Avalue;
    inc( result.ival);
end;

class operator TXalionRec.LessThan(ALeft, ARight: TXalionRec): boolean;
begin
      result:=False;
       if Aleft.ival<Aright.ival then
          result:=True;
end;

class operator TXalionRec.LessThanOrEqual(ALeft, ARight: TXalionRec): boolean;
begin
       result:=False;
       if Aleft.ival<=Aright.ival then
          result:=True;
end;

class operator TXalionRec.NotEqual(ALeft, ARight: TXalionRec): boolean;
begin
      result:=False;
       if Aleft.ival<>Aright.ival then
          result:=True;
end;



procedure TForm2.Button1Click(Sender: TObject);
var
   myrec,rec2:TXalionRec;
   d:Tdatetime;
begin

  myrec:=3;            //等于整数
   memo1.Lines.Add('myrec ival='+ myrec.ival.ToString);
  memo1.Lines.Add('myrec dval='+ formatdatetime('yyyy-mm-dd',myrec.dval));
  memo1.Lines.Add('>>>>>>>>>>>>>>>>>>end<<<<<<<<<<<<<<<<');


  inc(myrec);                 //递增
   memo1.Lines.Add('myrec ival='+ myrec.ival.ToString);
  memo1.Lines.Add('myrec dval='+ formatdatetime('yyyy-mm-dd',myrec.dval));
  memo1.Lines.Add('>>>>>>>>>>>>>>>>>>end<<<<<<<<<<<<<<<<');

  d:=2;
  myrec:=myrec+ d;                //加时间  2天
   memo1.Lines.Add('myrec ival='+ myrec.ival.ToString);
  memo1.Lines.Add('myrec dval='+ formatdatetime('yyyy-mm-dd',myrec.dval));
  memo1.Lines.Add('>>>>>>>>>>>>>>>>>>end<<<<<<<<<<<<<<<<');


  myrec:=myrec+5;       //加整数

  memo1.Lines.Add('myrec ival='+ myrec.ival.ToString);
  memo1.Lines.Add('myrec dval='+ formatdatetime('yyyy-mm-dd',myrec.dval));
  memo1.Lines.Add('>>>>>>>>>>>>>>>>>>end<<<<<<<<<<<<<<<<');

  rec2:=6;

  myrec:=myrec+rec2;


 memo1.Lines.Add('myrec ival='+ myrec.ival.ToString);
  memo1.Lines.Add('myrec dval='+ formatdatetime('yyyy-mm-dd',myrec.dval));
  memo1.Lines.Add('>>>>>>>>>>>>>>>>>>end<<<<<<<<<<<<<<<<');


end;

 

运行结果如图

可以看见非常灵活的实现各种操作,非常方便。

 

posted on 2018-11-10 14:19 xalion 阅读(...) 评论(...) 编辑 收藏