Question

该程序旨在从.txt文件中读取专辑信息，一旦用户输入了所需的曲目，该程序就会检查数组以查看其是否包含该曲目。我已经成功地将曲目读取到阵列中，但是我的程序无法识别字符串是否位于该阵列中。

Ruby文件

require './input_functions'
module Genre
  POP, CLASSIC, JAZZ, ROCK = *1..4
end

$genre_names = ['Null', 'Pop', 'Classic', 'Jazz', 'Rock']

class Album
    attr_accessor :title, :artist, :genre, :tracks

    def initialize (title, artist, genre)
        # insert lines here
        @title = title
        @artist = artist
        @genre = genre  
    end
end

class Track
    attr_accessor :name, :location
    def initialize (name, location)
        @name = name
        @location = location
    end
end

def read_track(music_file)
    track_name = music_file.gets
    track_location = music_file.gets
    track = Track.new(track_name, track_location)
end


def read_tracks(music_file)
    tracks = Array.new
    count = music_file.gets.to_i
    index = 0
while index < count
    tracks << read_track(music_file)
    index += 1
end
    tracks
end

def print_tracks(tracks)
    index = 0
    while (index < tracks.length)
    puts 'Track Number ' + index.to_s + ' is:'
    print_track(tracks[index])

    index = index + 1
end
    tracks
end

def read_album music_file
    album_artist = music_file.gets
    album_title = music_file.gets
    album_genre = music_file.gets
    album = Album.new(album_title, album_artist, album_genre)
    album
end


def print_album album

    puts 'Album title is ' + album.title.to_s
    puts 'Album artist is ' + album.artist.to_s
    puts 'Genre is ' + album.genre.to_s
    puts $genre_names[album.genre.to_i]
    # print out the tracks
    puts 'Tracks are ' + print_tracks(album.tracks).to_s

end


def print_track track
  puts('Track title is: ' + track.name.to_s)
    puts('Track file location is: ' + track.location.to_s)
end

** This is where I am having my problem
# search for track by name.
# Returns the index of the track or -1 if not found
def search_for_track_name(tracks, search_string)
    search_string = gets.chomp
    index = 0
while (index < tracks.length)
    tracks.include?(search_string)
    index = index + 1
end
    if tracks.include?(search_string)
        return index
    else
        index = -1

    end
    return index
end


# Reads in an Album from a file and then prints all the album
# to the terminal

def main

  music_file = File.new("album.txt", "r")
    if music_file
    album = read_album(music_file)
    album.tracks = read_tracks(music_file)
  music_file.close()
    end

  search_string = read_string("Enter the track name you wish to find: ")
  index = search_for_track_name(album.tracks, search_string)
  if index.to_i > -1
    puts "Found " + album.tracks[index].name + " at " + index.to_s
  else
    puts "Entry not Found"
  end
end
main

这是.txt文件

Neil Diamond
Greatest Hits
1
3
Crackling Rose
sounds/01-Cracklin-rose.wav
Soolaimon
sounds/06-Soolaimon.wav
Sweet Caroline
sounds/20-Sweet_Caroline.wav

当用户输入“ Sweet Caroline”时，程序应返回找到曲目的提示，而不是：

Enter the track name you wish to find:
Sweet Caroline

Entry not Found

Tracks are [#<Track:0x000000000331be58 @name="Crackling Rose\n", @location="sounds/01-Cracklin-rose.wav\n">, #<Track:0x000000000331bdb8 @name="Soolaimon\n", @location="sounds/06-Soolaimon.wav\n">, #<Track:0x000000000331bd18 @name="Sweet Caroline\n", @location="sounds/20-Sweet_Caroline.wav\n">]

Answer 1

条件if tracks.include?(search_string)永远不会是true，因为tracks是Track实例的数组。因此，该数组不包含特定的字符串。

它可能包含名称匹配的曲目。查找具有匹配名称Array#index的曲目的索引可能会有所帮助：

tracks.index { |track| track.name == search_string }

由于index返回nil（如果找不到），您可以简化整个if...else的块，将整个search_for_track_name方法的问题简化为这一行：

tracks.index { |track| track.name == search_string } || -1

Answer 2

我注意到您的搜索循环无效。它检查N次，如果数组中包含搜索字符串，则忽略该检查的结果，并将其添加到索引中。因此索引始终为N（在您的情况下为3）。然后再次检查数组是否包含搜索字符串，否则返回-1。因此，您的方法将始终返回N或-1。

幸运的是，Ruby是一种语言，已经为您完成了许多繁重的工作。坦率地说，我认为您想要：

def search_for_track_name(tracks, search_string)
  tracks.index(search_string) || -1
end

如果找不到搜索字符串，

#index将返回nil；这对于Ruby来说是更标准的，但是由于您的要求是返回-1，因此|| -1会为您添加它。（{nil和false是Ruby中 only 的伪造值，因此，如果第一部分是{{ 1}}。）

我也注意到了其他事情，我认为这可能是问题所在。您是否有机会必须按两次 Enter ？因为来自||的第一个输入将被nil覆盖。在将read_string传递给方法之前，您已经设置了它...

我注意到的第三件事-您的曲目名称填充了换行符（search_string = gets.chomp）。您还需要search_string，或者遵循其他用户的建议，寻找部分匹配而不是完全匹配。

无法在数组中搜索字符串

2 个答案: