Try Except异常实例

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function strtointrange(const s: string; min,max: longint): longint;
begin
  if (result < min) or (result > max) then
    raise ERangeError.CreateFmt('数值%d不在%d跟%d之间',[result,min,max]);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  try
    strtointrange('5',1,10);
  except
    on e: erangeerror do
      messagedlg(e.Message,mterror,[mbok],0);
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  try
    strtointrange('123',1,10);
  except
    on e: erangeerror do
      messagedlg(e.Message,mterror,[mbok],0);
  end;
end;

procedure TForm1.Button3Click(Sender: TObject);
var
  a,b: integer;
begin
  b := 0;
  try
    if (b = 0) then
      raise ezerodivide.Create('错误！除数不得为0！')
    else
      a := 10 div b;
    showmessage(inttostr(a));
  except
    on obj1: ezerodivide do
      messagedlg(obj1.Message,mterror,[mbok],0);
    on obj2: ezerodivide do
      messagedlg(obj2.Message,mterror,[mbok],0);
    else
      messagedlg('无法预知的错误！',mterror,[mbok],0);
  end;
end;

end.