一个没有了解透的简单函数: BoolToStr

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}

//以前不知道 BoolToStr 还有一个默认参数
procedure TForm1.Button1Click(Sender: TObject);
var
  b: Boolean;
  s: string;
begin
  b := True;
  s := BoolToStr(b);
  ShowMessage(s);         {-1}

  b := False;
  s := BoolToStr(b);
  ShowMessage(s);         {0}

  b := True;
  s := BoolToStr(b, True);
  ShowMessage(s);         {True}

  b := False;
  s := BoolToStr(b, True);
  ShowMessage(s);         {False}
end;

//以前还曾得意的这样用过, 笑话了.
procedure TForm1.Button2Click(Sender: TObject);
const
  b2s: array[Boolean] of string = ('False', 'True');
var
  b: Boolean;
  s: string;
begin
  b := True;
  s := b2s[b];
  ShowMessage(s); {True}

  b := not b;
  s := b2s[b];
  ShowMessage(s); {False}
end;

end.

SysUtils 单元下的公用函数目录

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