パスカル：ファイルから何も読み込まれずにエラーが発生する

Question

私は過去数時間、この作業をしようとしています。基本的に私の.datファイルから何も読み込まないので、オプション2、3、または4を使用しようとすると、ちょうどこれらが表示されます。

以下に.datファイルとパスカルを含めました。私は助けが切望されています。

mytestfile.dat

1 
Adele 
Pop 
2 
Hello 
ff 
Remedy 
dd 

ReadAlbum()手順においてパスカル

program MusicPlayer; 
uses TerminalUserInput; 

type 
    TrackRec = record 
     name: String; 
     location: String; 
    end; 
    // type TrackArray = array of TrackRec; 
    GenreType = (Pop, Rap, Rock, Classic); 
    AlbumRec = Record 
     name: String; 
     genre: GenreType; 
     // location: array of TrackRec; 
     tracks: array of TrackRec; 
    end; 
type AlbumArray = array of AlbumRec; 


function ReadGenre(): GenreType; 
var 
    option: Integer; 
begin 
    WriteLn('Press 1 for Pop'); 
    WriteLn('Press 2 for Rap'); 
    WriteLn('Press 3 for Rock'); 
    WriteLn('Press 4 for Classic'); 
    option := ReadInteger(''); 

    while (option<1) or (option>5) do 
    begin 
     WriteLn('Please enter a number between 1-4'); 
     option := ReadInteger(''); 
    end; 

    case option of 
     1: result := Pop; 
     2: result := Rap; 
     3: result := Rock; 
    else 
     result := Classic; 
    end; 
end; 

procedure NewAlbum(var albums: AlbumArray; var myFile: TextFile); 
var 
    number, i, tracks, y: Integer; 
begin 
    AssignFile(myFile, 'mytestfile.dat'); 
    ReWrite(myFile); 

    number := ReadInteger('How many albums do you want to make?: '); 
    WriteLn(myFile, number); 
    SetLength(albums, number); 

    for i := Low(albums) to High(albums) do 
    begin 
     albums[i].name := ReadString('Enter album name:'); 
     WriteLn(myFile, albums[i].name); 

     albums[i].genre := ReadGenre(); 
     WriteLn(myFile, albums[i].genre); 

     tracks := ReadIntegerRange('How many tracks do you want to enter? (max 15)', 0, 15); 
     WriteLn(myFile, tracks); 
     SetLength(albums[i].tracks, tracks); 

     for y := Low(albums[i].tracks) to tracks - 1 do 
     begin 
      albums[i].tracks[i].name := ReadString('Track name:'); 
      WriteLn(myFile, albums[i].tracks[i].name); 
      albums[i].tracks[i].location := ReadString('Track Location:'); 
      WriteLn(myFile, albums[i].tracks[i].location); 
     end; 
    end; 
    Close(myFile); 
end; 

procedure ReadTrack(count: Integer; var albums: AlbumArray; var myFile: TextFile); 
var 
    i: Integer; 
begin 
    ReadLn(myFile, i); 
    SetLength(albums[count].tracks, i); 
    for count := Low(albums[count].tracks) to High(albums[count].tracks) - 1 do 
    begin 
     ReadLn(myFile, albums[count].tracks[i].name); 
     ReadLn(myFile, albums[count].tracks[i].location); 
    end; 
end; 

procedure ReadAlbum(var albums: AlbumArray; var myFile: TextFile); 
var 
    albumNumber, tracknumber, count, i: Integer; 

begin 
    AssignFile(myFile, 'mytestfile.dat'); 
    Reset(myFile); 
    ReadLn(myFile, albumNumber); 
    SetLength(albums, albumNumber); 

    for i := Low(albums) to High(albums) do 
    begin 
     ReadLn(myFile, albums[i].name); 
     ReadLn(myFile, albums[i].genre); 
     ReadLn(myFile, tracknumber); 
     SetLength(albums[i].tracks, tracknumber); 
     for count := Low(albums[count].tracks) to tracknumber - 1 do 
     begin 
      ReadLn(myFile, albums[count].tracks[i].name); 
      ReadLn(myFile, albums[count].tracks[i].location); 
     end; 
    end; 
end; 

procedure ReadAlbums(var albums: AlbumArray; var myFile: TextFile); 
var 
    i, number: Integer; 
begin 
    ReadAlbum(albums, myFile); 
    WriteLn('Album is:'); 
    for i := Low(albums) to High(albums) do 
    begin 
     WriteLn((i + 1),'.', albums[i].name); 
     WriteLn('.', albums[i].genre); 
     for number := Low(albums[i].tracks) to High(albums[i].tracks) do 
     begin 
      WriteLn((number + 1), '', albums[i].tracks[Low(albums[i].tracks)].name); 
     end; 
    end; 
end; 

procedure PlayAlbum (var albums: AlbumArray; var myFile: TextFile); 
var 
    i, number: Integer; 
begin 

    ReadAlbums(albums, myFile); 

    i := ReadInteger('Please select an album: '); 
    i := i - 1; 
    number := ReadIntegerRange('Please select a song from album:', 1, 20); 
    number := number - 1; 

    WriteLn('Now playing'); 
    WriteLn('Track selected: ', albums[i].tracks[number].name); 
    WriteLn('Album: ', albums[i].name); 

end; 

procedure Update(var albums: AlbumArray; var myFile: TextFile); 
var 
    i: Integer; 
begin 
    ReadAlbums(albums, myFile); 
    i := ReadInteger('Select an album to update'); 
    i := i - 1; 
    albums[i].name := ReadString('New Album Name:'); 
    WriteLn('Album has now been updated'); 
end; 

procedure Main(); 
var 
    i, count, select, change: Integer; 
    albums: AlbumArray; 
    myFile: TextFile; 
begin 

    WriteLn('Please select an option: '); 
    WriteLn('-------------------------'); 
    WriteLn('1. Read Albums'); 
    WriteLn('2. Display Albums'); 
    WriteLn('3. Select an Album'); 
    WriteLn('4. Update an Album'); 
    WriteLn('5. Exit'); 
    WriteLn('-------------------------'); 
    repeat 
     i := ReadInteger('Select option for menu:'); 
     case i of 
      1: ReadAlbum(albums, myFile); 

      2: ReadAlbums(albums, myFile); 

      3: PlayAlbum(albums, myFile); 

      4: Update(albums, myFile); 
     end; 
    until i = 5; 
end; 

begin 
    Main(); 
end. 

Answer 1

次の2つのforループ、アルバムおよびトラックをループ内側のをループ外いずれかを有しています。

これは誤ったコードは次のとおりです：

for count := Low(albums[count].tracks) to tracknumber - 1 do 
    begin 
     ReadLn(myFile, albums[count].tracks[i].name); 
     ReadLn(myFile, albums[count].tracks[i].location); 
    end; 

albums[]指標としてiを使用する必要がありますし、tracks[]はインデックスとしてcountを使用する必要があり、後者では、インデックスを台無しにしています。

あなたは私はあなたが例えば、明確な意味を持つあなたの変数に名前を示唆配列とインデックスにより慣れるまで：

`NumOfAlbums` in the meaning of how many albums you have 
`AlbumIndex` as the index to the albums array 
`NumOfTracks` as the number of tracks in an album 
`TrackIndex` as the index to the tracks array 

それはとても長い名前を書くのは面倒に感じるかもしれないが、あなたはおそらく持っていません間違った名前を付けて、間違いを犯しました。