当我把一个"结构体"在类中当做属性后, 在实用中可以直接读取结构体成员, 但不能直接写入...
下面是由此引发的小练习:
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
Button3: TButton;
Button4: TButton;
Button5: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button5Click(Sender: TObject);
end;
TMyClass = class
strict private
FPos: TPoint;
procedure SetPos(const Value: TPoint);
public
property Pos: TPoint read FPos write SetPos; //属性 Pos 对应一个点结构
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TMyClass }
procedure TMyClass.SetPos(const Value: TPoint);
begin
FPos := Value;
end;
{测试}
procedure TForm1.Button1Click(Sender: TObject);
var
obj: TMyClass;
begin
obj := TMyClass.Create;
ShowMessageFmt('%d, %d', [obj.Pos.X, obj.Pos.Y]); //可以直接访问结构中的元素
// obj.Pos.X := 11; //但不能直接给结构中的元素赋值
// obj.Pos.Y := 22;
obj.Free;
end;
//变通一
procedure TForm1.Button2Click(Sender: TObject);
var
obj: TMyClass;
begin
obj := TMyClass.Create;
obj.Pos := Point(22,33); //
ShowMessageFmt('%d, %d', [obj.Pos.X, obj.Pos.Y]);
obj.Free;
end;
//变通二
procedure TForm1.Button3Click(Sender: TObject);
var
obj: TMyClass;
pt: TPoint;
begin
obj := TMyClass.Create;
pt.X := 33;
pt.Y := 44;
obj.Pos := pt;
ShowMessageFmt('%d, %d', [obj.Pos.X, obj.Pos.Y]);
obj.Free;
end;
//变通三(假如属性的 get 不是方法)
procedure TForm1.Button4Click(Sender: TObject);
var
obj: TMyClass;
p: PPoint;
begin
obj := TMyClass.Create;
p := Addr(obj.Pos);
p.X := 44;
p.Y := 55;
ShowMessageFmt('%d, %d', [obj.Pos.X, obj.Pos.Y]);
obj.Free;
end;
//变通四(假如属性的 get 不是方法)
procedure TForm1.Button5Click(Sender: TObject);
var
obj: TMyClass;
begin
obj := TMyClass.Create;
PPoint(Addr(obj.Pos)).X := 55;
PPoint(Addr(obj.Pos)).Y := 66;
ShowMessageFmt('%d, %d', [obj.Pos.X, obj.Pos.Y]);
obj.Free;
end;
end.
练习二:
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
TMyClass = class
private
FPos: TPoint;
function GetPos: TPoint;
procedure SetPos(const Value: TPoint);
function GetXY(const Index: Integer): Integer;
procedure SetXY(const Index, Value: Integer);
public
property Pos: TPoint read GetPos write SetPos;
property X: Integer index 0 read GetXY write SetXY;
property Y: Integer index 1 read GetXY write SetXY;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TMyClass }
function TMyClass.GetPos: TPoint;
begin
Result := FPos;
end;
procedure TMyClass.SetPos(const Value: TPoint);
begin
FPos := Value;
end;
function TMyClass.GetXY(const Index: Integer): Integer;
begin
Result := 0;
case Index of
0: Result := FPos.X;
1: Result := FPos.Y;
end;
end;
procedure TMyClass.SetXY(const Index, Value: Integer);
begin
case Index of
0: FPos.X := Value;
1: FPos.Y := Value;
end;
end;
{测试}
procedure TForm1.FormCreate(Sender: TObject);
var
obj: TMyClass;
begin
obj := TMyClass.Create;
obj.X := 11;
obj.Y := 22;
ShowMessageFmt('%d, %d', [obj.Pos.X, obj.Pos.Y]);
obj.Free;
end;
end.
posted @ 2012-01-05 16:56 万一 阅读(427) 评论(1)
编辑
在实践中真的会发现更多问题.
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
IA = Interface
function GetName: string;
property Name: string read GetName;
end;
TC1 = class(TInterfacedObject, IA)
function GetName: string; virtual;
end;
TC2 = class(TC1)
function GetName: string; override; //覆盖
end;
TC3 = class(TC2)
function GetName: string; override; //再覆盖
end;
TC4 = class(TC3)
function GetName: string; override; //再覆盖
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TC1 }
function TC1.GetName: string;
begin
Result := 'C1';
end;
{ TC2 }
function TC2.GetName: string;
begin
Result := 'C2';
end;
{ TC3 }
function TC3.GetName: string;
begin
Result := 'C3';
end;
{ TC4 }
function TC4.GetName: string;
begin
Result := inherited + '0';
end;
{测试}
procedure TForm1.FormCreate(Sender: TObject);
var
v1,v2,v3,v4: IA;
begin
v1 := TC1.Create;
v2 := TC2.Create;
v3 := TC3.Create;
v4 := TC4.Create;
ShowMessageFmt('%s, %s, %s, %s', [v1.Name, v2.Name, v3.Name, v4.Name]); //C1, C2, C3, C30
end;
end.
posted @ 2012-01-03 22:09 万一 阅读(381) 评论(2)
编辑
在今后的 Delphi 中, 以接口、结构为主的设计应该会越来越多, 因为这样太方便了.
System.RegularExpressions 就是以结构为主体设计的非常好的示范; 但更多东西使用接口会更合适.
有见过他人早就使用接口写程序, 从手头的这个程序开始我才开始使用.
现在基本总结出四种框架模式: 1、直接实现; 2、间接实现(或叫继承实现); 3、覆盖实现; 4、委托实现.
一、直接实现:
下例中虽有 TMy1、TMy2, 但在具体应用中使用的应是 IMy1、IMy2, 这就是我所谓的以接口为主导.
TMy1、TMy2 直接实现了所属接口的所有方法, 这是我所谓的直接实现.
这样可能会有代码重复, 但如果程序很小, 还是挺实用的.
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
IA = Interface
procedure Method_A;
end;
IB = Interface(IA)
procedure Method_B;
end;
IMy1 = Interface(IB)
procedure Method_My1;
end;
IMy2 = Interface(IB)
procedure Method_My2;
end;
TMy1 = class(TInterfacedObject, IMy1)
procedure Method_A;
procedure Method_B;
procedure Method_My1;
end;
TMy2 = class(TInterfacedObject, IMy2)
procedure Method_A;
procedure Method_B;
procedure Method_My2;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TMy1 }
procedure TMy1.Method_A;
begin
ShowMessage('A');
end;
procedure TMy1.Method_B;
begin
ShowMessage('B');
end;
procedure TMy1.Method_My1;
begin
ShowMessage('My1');
end;
{ TMy2 }
procedure TMy2.Method_A;
begin
ShowMessage('A');
end;
procedure TMy2.Method_B;
begin
ShowMessage('B');
end;
procedure TMy2.Method_My2;
begin
ShowMessage('My2');
end;
{测试}
procedure TForm1.FormCreate(Sender: TObject);
var
v1: IMy1;
v2: IMy2;
begin
v1 := TMy1.Create;
v1.Method_A;
v1.Method_B;
v1.Method_My1;
v2 := TMy2.Create;
v2.Method_A;
v2.Method_B;
v2.Method_My2;
end;
end.
二、间接实现:
下面例子通过一个间接的 TB 类, 避免了 TMy1、TMy2 中可能会重复的代码.
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
IA = Interface
procedure Method_A;
end;
IB = Interface(IA)
procedure Method_B;
end;
TB = class(TInterfacedObject, IB)
procedure Method_A;
procedure Method_B;
end;
IMy1 = Interface(IB)
procedure Method_My1;
end;
IMy2 = Interface(IB)
procedure Method_My2;
end;
TMy1 = class(TB, IMy1)
procedure Method_My1;
end;
TMy2 = class(TB, IMy2)
procedure Method_My2;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TB }
procedure TB.Method_A;
begin
ShowMessage('A');
end;
procedure TB.Method_B;
begin
ShowMessage('B');
end;
{ TMy1 }
procedure TMy1.Method_My1;
begin
ShowMessage('My1');
end;
{ TMy2 }
procedure TMy2.Method_My2;
begin
ShowMessage('My2');
end;
{测试}
procedure TForm1.FormCreate(Sender: TObject);
var
v1: IMy1;
v2: IMy2;
begin
v1 := TMy1.Create;
v1.Method_A;
v1.Method_B;
v1.Method_My1;
v2 := TMy2.Create;
v2.Method_A;
v2.Method_B;
v2.Method_My2;
end;
end.
三、覆盖实现:
从 TB 继承的过程中当然也可以通过覆盖虚函数而实现多态, 下面的 TMy2 就这么做了.
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
IA = Interface
procedure Method_A;
end;
IB = Interface(IA)
procedure Method_B;
end;
TB = class(TInterfacedObject, IB)
procedure Method_A; virtual;
procedure Method_B; virtual;
end;
IMy1 = Interface(IB)
procedure Method_My1;
end;
IMy2 = Interface(IB)
procedure Method_My2;
end;
TMy1 = class(TB, IMy1)
procedure Method_My1;
end;
TMy2 = class(TB, IMy2)
procedure Method_A; override;
procedure Method_B; override;
procedure Method_My2;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TB }
procedure TB.Method_A;
begin
ShowMessage('A');
end;
procedure TB.Method_B;
begin
ShowMessage('B');
end;
{ TMy1 }
procedure TMy1.Method_My1;
begin
ShowMessage('My1');
end;
{ TMy2 }
procedure TMy2.Method_A;
begin
ShowMessage('A_My2');
end;
procedure TMy2.Method_B;
begin
ShowMessage('B_My2');
end;
procedure TMy2.Method_My2;
begin
ShowMessage('My2');
end;
{测试}
procedure TForm1.FormCreate(Sender: TObject);
var
v1: IMy1;
v2: IMy2;
begin
v1 := TMy1.Create;
v1.Method_A;
v1.Method_B;
v1.Method_My1;
v2 := TMy2.Create;
v2.Method_A;
v2.Method_B;
v2.Method_My2;
end;
end.
四、委托实现:
接口中的方法是肯定要实现的, 但也可以通过 implements 关键字借用(或叫委托)其它的实现;
但, 官方文档说这只适用于 Win32. 就是说这种方法在 Win64 和其它系统都不行, 还学它干嘛?
posted @ 2012-01-03 18:01 万一 阅读(513) 评论(1)
编辑
2011 年的最后一天了...
混合排序 -> 搅乱、重新洗牌; 以 Integer 动态数组为例.
//两个辅助函数 Swap、ToStr, 分别用于交换数组元素和呈现为字符串
procedure Swap(var Arr: TArray<Integer>; a,b: Cardinal);
var
tmp: Integer;
begin
if (a >= Length(Arr)) or (b >= Length(Arr)) or (a = b) then Exit;
tmp := Arr[a];
Arr[a] := Arr[b];
Arr[b] := tmp;
end;
function ToStr(const Arr: TArray<Integer>): string;
var
n: Integer;
begin
for n in Arr do
Result := Result + IntToStr(n) + sLineBreak;
end;
//-----------------------------------------------------------------
{1、简单反排序}
procedure SimpleShuffle(var Arr: TArray<Integer>);
var
r,i: Integer; //分别用作随机索引、遍历索引
begin
for i := 0 to Length(Arr) - 1 do
begin
r := Random(Length(Arr));
Swap(Arr, i, r);
end;
end;
{2、好的反排序}
procedure GoodShuffle(var Arr: TArray<Integer>);
var
r,i: Integer;
begin
for i := Length(Arr) - 1 downto 0 do
begin
r := Random(i + 1);
if r <> i then Swap(Arr, i, r);
end;
end;
{测试}
procedure TForm1.Button1Click(Sender: TObject);
var
arr1,arr2: TArray<Integer>;
begin
arr1 := TArray<Integer>.Create(0, 1, 2, 3, 4, 5, 6, 7, 8, 9); //
arr2 := Copy(arr1); //
// SimpleShuffle(arr2);
GoodShuffle(arr2);
Memo1.Text := ToStr(arr1);
Memo2.Text := ToStr(arr2);
end;
posted @ 2011-12-31 13:30 万一 阅读(359) 评论(1)
编辑
uses IdHTTP;
const Url = 'http://del.cnblogs.com';
procedure TForm1.Button1Click(Sender: TObject);
var
stream: TStringStream;
idHttpObj: TIdHTTP;
begin
stream := TStringStream.Create('', TEncoding.UTF8); //
idHttpObj := TIdHTTP.Create(nil);
idHttpObj.Get(Url, stream);
idHttpObj.Free;
Memo1.Text := stream.DataString;
stream.Free;
end;
posted @ 2011-12-30 20:54 万一 阅读(391) 评论(4)
编辑