Delphi 中的 IfThen 函数 - 回复 "深挖洞、广积粮" 的问题

unit Unit1;

interface

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

type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

uses StrUtils, Math;

procedure TForm1.Button1Click(Sender: TObject);
var
a: Integer;
str: string;
begin
a := 1;
str := StrUtils.IfThen(a > 0, 'aaa', 'bbb');
ShowMessage(str); {aaa}

a := -1;
str := StrUtils.IfThen(a > 0, 'aaa', 'bbb');
ShowMessage(str); {bbb}

a := 1;
str := StrUtils.IfThen(a > 0, 'aaa');
ShowMessage(str); {aaa}

a := -1;
str := StrUtils.IfThen(a > 0, 'aaa');
ShowMessage(str); {}
end;

procedure TForm1.Button2Click(Sender: TObject);
var
str: string;
num: Integer;
begin
str := '万一';
num := Math.IfThen(str <> '', 99, 11);
ShowMessage(IntToStr(num)); {99}

str := '';
num := Math.IfThen(str <> '', 99, 11);
ShowMessage(IntToStr(num)); {11}

str := '万一';
num := Math.IfThen(str <> '', 99);
ShowMessage(IntToStr(num)); {99}

str := '';
num := Math.IfThen(str <> '', 99);
ShowMessage(IntToStr(num)); {0}
end;

end.