如何使用 Perl 6 类表示嵌套数据结构？

Question

上次我必须处理此类数据时，我使用了诸如哈希数组之类的东西，其中每个哈希都可以有哈希值等。在遍历不同的索引/键时，很难不迷路，所以我认为应该有更好的解决方案。由于我没有 OOP 方面的经验，我不知道如何开始...

假设在我们的城市，我们有一个 Library（其内容已被数字化为 txt 文件）有几个房间：1_red_room、2_blue_room 和 3_white_room。每个房间里都有很多书，每个book有：author's_name、title和text（从txt文件中读取）分为pages（带数字）。

给定$word，对于每个房间，程序应该列出：

room_name, with the overall number of `$word` contexts in all its books
  list of authors, who use this word, with number of contexts
    for every author, list of books, with number of contexts
      for every book, list of pages, with number of contexts

输出示例：

Word: cucumber
TOTAL: 654
1_red_room: 234
  author: John Smith: 70
    title: "In the wild": 3
      page_50:  1
      page_150: 2
    title: "Hello world": 10
      page_1: 2
      page_5: 1
      page_7: 3
...
...
2_blue_room: 114
  author: Wendy Brown
    title: "In the dark": 43
      page_8: 7
...

那么，有没有办法在用户定义的类（或者可能使用其他工具）的帮助下处理这些数据？

Answer 1

这是我将如何开始的。我会创建一个Book 类。然后我会为每个房间创建一个书籍哈希%books：

my $total-count = 0;
my @room-info;
for @rooms -> $room {
    my @room-authors;
    my %room-authors;
    my $room-count = 0;
    for @(%books{$room}) -> $book {
        my $count = $book.contains-word( $word );
        if $count > 0 {
            $total-count += $count;
            $room-count += $count;
            my $author = $book.author;
            if %room-authors{$author}:exists {
                $(%room-authors{$author}).update($book, $word, $count);
            }
            else {
                %room-authors{$author} = Room-Author.new(
                    book => $book, word => $word, count => $count
                );
                @room-authors.push( $author );
            }
        }
    }
    if @room-authors.elems > 0 {
        @room-info.push(
            Room-Info.new(
                room => $room, room-count => $room-count,
                order => @room-authors, hash => %room-authors
            )
        );
    }
}
say "Word: $word";
say "TOTAL: $total-count";

for @room-info -> $room {
    my @room-authors = $room.order;
    my %room-authors = $room.hash;
    say $room.room ~ " : " ~ $room.room-count;
    for @room-authors -> $author-str {
        my $author = %room-authors{$author-str};
        say "  author: " ~ $author.name ~ " : " ~ $author.count;
        for @($author.titles) -> $title {
            say "    title: " ~ $title.title ~ " : " ~ $title.count;
            for @($title.pages) -> $page {
                say "      page_" ~ $page.page ~ ": " ~ $page.count;
            }
        }
    }
}

这里Page、Title、Room-Info、Book和Room-Author类可能看起来像（注意：更多细节必须用真实代码填写）：

class Page {
    has Int $.page;
    has Int $.count;
}

class Title {
    has Str $.title;
    has Page @.pages;
    has Int $.count;
}

class Room-Info {
    has $.room;
    has $.room-count;
    has @.order;
    has %.hash;
}

class Book {
    has Str $.author;
    has Str $.title;
    has Str $.text;

    # checks how many times a word occurs in the book
    method contains-word ( $word, --> Int ) {
        return 2;  # Stub, insert more code here..
    }

    method get-page-matches( $word ) {
        return [Page.new(page => 50, count => 1),
                Page.new(page => 150, count => 2)]; # Stub, insert more code..
    }
}

class Room-Author {
    has Title @.titles;
    has Bool %!titles;
    has $.name;
    has $.count;

    submethod BUILD(:$book, :$word, :$!count) {
        my $title = $book.title;
        $!name = $book.author;
        %!titles{$title} = True;
        @!titles.push(
            Title.new(title => $title,
                      pages => $book.get-page-matches( $word ),
                      count => $!count,
                     )
        );
    }
    method update( $book, $word, $count ) {
        my $title = $book.title;
        $!count += $count;
        my $author = $book.author; # should be the same as $.name.. 
        if %!titles{$title}:exists {
            die "Unexpected: Duplicate title '$title' for $author";
        }
        else {
            %!titles{$title} = True;
            my Page @pages = $book.get-page-matches( $word );
            @!titles.push(
                Title.new(title => $title,
                          pages => $book.get-page-matches( $word ),
                          count => $count,
                         ) );
        }
    }
}