测试 TStreamWriter、TStreamReader

TStreamWriter 和 TStringWriter 都是继承于抽象类: TTextWriter;
TStreamReader 和 TStringReader 都是继承于抽象类: TTextReader.

它们的功能相似, 不过 TStreamWriter、TStreamReader 又有了 "流" 的特性, 比较适合对字符串流的读写.

---

unit Unit1;



interface



uses

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

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    Button3: TButton;

    Button4: TButton;

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

    procedure Button3Click(Sender: TObject);

    procedure Button4Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



const FilePath = 'c:\temp\test.txt';



//貌似是流操作, 其实写入的非字符串类型也都转换成了字符串

procedure TForm1.Button1Click(Sender: TObject);

var

  Writer: TStreamWriter;

  Reader: TStreamReader;

begin

  Writer := TStreamWriter.Create(FilePath);

  Writer.WriteLine('string');

  Writer.WriteLine(123);

  Writer.WriteLine(True);

  Writer.WriteLine(3.14);

  Writer.Close;

  Writer.Free;



  Reader := TStreamReader.Create(FilePath);

  ShowMessage(Reader.ReadToEnd);

  Reader.Close;

  Reader.Free;

end;



//读写时可指定字符编码

procedure TForm1.Button2Click(Sender: TObject);

var

  Writer: TStreamWriter;

  Reader: TStreamReader;

begin

  {参数 2 如果是 True 将会在已有文件的后面添加; False 是新建文件}

  Writer := TStreamWriter.Create(FilePath, False, TEncoding.Unicode);

  Writer.WriteLine('万一的 Delphi 博客');

  Writer.Close;

  Writer.Free;



  Reader := TStreamReader.Create(FilePath, Tencoding.Unicode);

  ShowMessage(Reader.ReadToEnd);

  Reader.Close;

  Reader.Free;

end;



//不指定编码时, 默认的是 UTF8

procedure TForm1.Button3Click(Sender: TObject);

var

  Writer: TStreamWriter;

  Reader: TStreamReader;

begin

  Writer := TStreamWriter.Create(FilePath);

  Writer.Write('万一的 Delphi 博客');

  Writer.Close;

  Writer.Free;



  Reader := TStreamReader.Create(FilePath);

  ShowMessage(Reader.CurrentEncoding.ClassName); {TUTF8Encoding}

  Reader.EndOfStream;

  Reader.Close;

  Reader.Free;

end;



//可基于另一个 TStream 创建; 从 BaseStream 上看它的确就是个流

procedure TForm1.Button4Click(Sender: TObject);

var

  Writer: TStreamWriter;

  Reader: TStreamReader;

begin

  Writer := TStreamWriter.Create(TFileStream.Create(FilePath, fmCreate), TEncoding.UTF8);

  Writer.Write('万一的 Delphi 博客');

  Writer.BaseStream.Free;

  Writer.Close;

  Writer.Free;



  Reader := TStreamReader.Create(TFileStream.Create(FilePath, fmOpenRead), TEncoding.UTF8);

  ShowMessage(Reader.ReadLine); {万一的 Delphi 博客}

  Reader.BaseStream.Free;

  Reader.Close;

  Reader.Free;

end;



end.