Invoke 类型转换错误

hdj_myth 2011-12-20 10:34:44



unit Unit3;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm3 = class(TForm)

    mo1: TMemo;

    btn1: TButton;

    btn2: TButton;

    btn3: TButton;

    btn4: TButton;

    procedure btn1Click(Sender: TObject);

    procedure btn2Click(Sender: TObject);

    procedure btn3Click(Sender: TObject);

    procedure btn4Click(Sender: TObject);

  private

    { Private declarations }

  public

    procedure say(str: string);

  end;



var

  Form3: TForm3;



implementation



{$R *.dfm}



uses

  Rtti;



procedure TForm3.btn1Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

begin

  mo1.Clear;

  for t in ctx.GetTypes do

    mo1.Lines.Add(t.Name);

end;



procedure TForm3.btn2Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

  m: TRttiMethod;

begin

  mo1.Clear;

  t := ctx.GetType(TForm3);

  for m in t.GetMethods do

    mo1.Lines.Add(m.Name);

end;



procedure TForm3.btn3Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

  f: TRttiField;

begin

  mo1.Clear;

  t := ctx.GetType(TButton);

  for f in t.GetFields do

    mo1.Lines.Add(f.Name);

end;



procedure TForm3.btn4Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

  m: TRttiMethod;

  V: TValue;

begin

  t := ctx.GetType(TForm3);

  m := t.GetMethod('say');

  V := TValue.From<string>('123');

  m.Invoke(TForm3, V);//此处报错Invalid class typecast.

end;



procedure TForm3.say(str: string);

begin

  mo1.Clear;

  mo1.Lines.Add(str);

end;

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Jekhn 2011-12-20

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是Form3不是TForm3，你得注意一下动态数组的下标是从0开始的不是1

hdj_myth 2011-12-20

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自己解决了

hdj_myth 2011-12-20

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unit Unit3;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm3 = class(TForm)

    mo1: TMemo;

    btn1: TButton;

    btn2: TButton;

    btn3: TButton;

    btn4: TButton;

    procedure btn1Click(Sender: TObject);

    procedure btn2Click(Sender: TObject);

    procedure btn3Click(Sender: TObject);

    procedure btn4Click(Sender: TObject);

  private

    { Private declarations }

  public

    procedure say(str: string);

  end;



var

  Form3: TForm3;



implementation



{$R *.dfm}



uses

  Rtti;



procedure TForm3.btn1Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

begin

  mo1.Clear;

  for t in ctx.GetTypes do

    mo1.Lines.Add(t.Name);

end;



procedure TForm3.btn2Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

  m: TRttiMethod;

begin

  mo1.Clear;

  t := ctx.GetType(TForm3);

  for m in t.GetMethods do

    mo1.Lines.Add(m.Name);

end;



procedure TForm3.btn3Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

  f: TRttiField;

begin

  mo1.Clear;

  t := ctx.GetType(TButton);

  for f in t.GetFields do

    mo1.Lines.Add(f.Name);

end;



procedure TForm3.btn4Click(Sender: TObject);

var

  ctx: TRttiContext;

  t: TRttiType;

  m: TRttiMethod;

  V: array of TValue;

begin

  t := ctx.GetType(TForm3);

  m := t.GetMethod('say');

  SetLength(V, 1);

  V[1] := TValue.From<string>('123');

  m.Invoke(TForm3, V);//此处报错Invalid class typecast.

end;



procedure TForm3.say(str: string);

begin

  mo1.Clear;

  mo1.Lines.Add(str);

end;



end.