Ich habe eine undefinierte Methode.Nicht definierte Methode `<< 'für Null: NilClass (NoMethodError)
rb:31:in `add_song': undefined method `<<' for nil:NilClass (NoMethodError)
Ich verstehe, dass @library[artist]
gibt nil
, aber ich verstehe nicht, warum und weiß nicht, wie es zu beheben. Irgendein Rat?
module Promptable
def prompt(message = "What music would you like to add", symbol = ":>")
print message
print symbol
gets.chomp
end
end
class Library
attr_accessor :artist, :song
def initialize
@library = {}
end
def add_artist(artist)
@library[artist] = []
end
def add_song(song)
@library[artist] << song
end
def show
puts @library
end
end
class Artist
attr_accessor :name, :song
def initialize(artist)
@name = artist[:name]
@song = artist[:song]
end
def to_s
"#{name}, #{song}"
end
end
if __FILE__ == $PROGRAM_NAME
include Promptable
include Menu
my_library = Library.new
my_library.add_artist(Artist.new(:name => prompt("What it the artist name ?")))
my_library.add_song(Artist.new(:song => prompt("What is the song name ?")))
my_library.show
end