Question

在过去的几个小时里，我一直在强调试图让这个工作起来，我简直无法理解。基本上它不会从我的.dat文件中读取任何内容，当我尝试使用选项2,3或4时，它只是提出了这些

errors 。

我在下面包含.dat文件和pascal。我迫切需要帮助。

mytestfile.dat

1
Adele
Pop
2
Hello
ff
Remedy
dd

帕斯卡

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

在ReadAlbum()程序中，您有两个for循环，一个循环遍历专辑的外部循环和一个循环通过曲目的内部循环。在后者中，你搞砸了索引：

这是错误的代码：

    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[]应使用i作为索引，tracks[]应使用count作为索引。

在您习惯使用数组和索引之前，我建议您使用明确的含义命名变量，例如：

`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

写这么长的名字可能会让人感到厌倦，但是你可能不会犯这样的错误，用更详细的名字。

Pascal：不会从我的文件中读取任何内容并收到错误

1 个答案: