I'm working on a Ruby project for a text based adventure game and have encountered an issue when trying to use the 'find' method in Ruby.
I've got a location class that all locations are instantiated from. Each location has a set of two coordinates, ([x, y] = [1, 1]) and the player also has their own set of coordinates to store where they are actually located.
The class method & initialise method
def self.findLocation(coord, attributeToPrint)
puts coord.inspect
puts ##finder.find { coord }.inspect
end
def initialize(newTitle, newDescription, newCoord)
#title = newTitle
#description = newDescription
#coordinate = newCoord
##finder << self
end
What I'm trying to do is store all of the locations in an array and have a class method for printing out the title and description of a location by using the find method to select the location with the matching coordinates to the player. The method I currently have passes the player's coordinate in coord parameter and uses the find method to check the array (which has all location objects within it) for the coordinate.
I've found many questions relating to this method but have had no success with any of the solutions found on these questions and no luck with any solution of my own. If I try and use a comparison statement such as #coordinate == coord the method will simply return nil and my current version returns an object, but only the object which is first in the array and does not return the location with the matching #coordinate attribute.
I would greatly appreciate any help with this issue as it is the main roadblock to making some progress on the text adventure game and allowing some interactivity. I am sure that I am using this method incorrectly and don't understand how it functions but the enumerator documentation hasn't helped me very much after looking at it and there is possibly a much better way of implementing this over a class method.
Reproducing the Issue
Location class (necessary parts)
class Location
##finder = Array.new
def self.findLocation(coord, attributeToPrint)
puts coord.inspect
puts ##finder.find { coord }.inspect
end
#Initialise locations here
def initialize(newTitle, newDescription, newCoord)
#title = newTitle
#description = newDescription
#coordinate = newCoord
##finder << self
end
Player class (necessary parts)
class Player
def initialize(playerHealth, playerLocation, playerInventory)
#health = playerHealth
#location = playerLocation
#inventory = playerInventory
end
Main script (necessary parts)
require_relative '../lib/player'
require_relative '../lib/location'
start = Location.new('Test 1', 'This is test 1.', [0, 0])
start2 = Location.new('Test 2', 'This is test 2.', [1,1])
start3= Location.new('Test 3', 'This is test 3.', [2, 2])
player = Player.new(100, [1,1], ['sword'])
#Input loop
loop do
Location.findLocation(player.getLocation, 'example')
end
You have to specify how find will match the stored records against the provided value. Specifically, you need to compare coord to the record's coord. To access the record's coord you need a getter method.
class Location
def self.findLocation(coord, attributeToPrint)
puts coord.inspect
puts ##finder.find { |location| location.coord == coord }.inspect
end
def coord
#coord
end
end
The way that find works is that it executes the block for every instance in the array, returning the first array element where the result is 'truthy' (i.e. not nil and not false). When you do { coord } the block returns the coord value immediately. coord is not nil and not false, so the first record is selected. When you did #coord == coord the #coord is undefined at the class level (it's nil) and so for all records the comparison was false so no record was selected, hence your nil result.
To print a specific attribute (say, title) you can also access the attribute with the getter method. and then send that method to the object.
class Location
def self.findLocation(coord, attributeToPrint)
puts coord.inspect
found_location = ##finder.find { |location| location.coord == coord }
puts found_location.send(attributeToPrint) if found_location
end
def coord
#coord
end
def title
#title
end
end
So now you can do...
Location.findLocation([1,1], 'title')
However...
It's much more flexible to have findLocation only be responsible for returning the object and then output the attribute outside the method... single responsibility principle...
class Location
def self.findLocation(coord)
##finder.find { |location| location.coord == coord }
end
def coord
#coord
end
def title
#title
end
end
So now you can do...
player_location = Location.findLocation([1,1])
puts player_location.title if player_location
Related
In ruby I have created a class and array, to read the contents from a text file then output them.
class Album
attr_accessor :artist, :title, :genre, :tracks
end
album = Album.new(album_title, album_artist, album_genre, tracks)
-> tracks is an array of multiple lines read from the text file using a while loop. Context below, a_file/music_file File.new("album.txt", "r")
class Track
attr_accessor :name, :location
def read_track(a_file)
track_title = a_file.gets()
track_location = a_file.gets()
track = Track.new(track_title, track_location)
end
def read_tracks(music_file)
tracks = Array.new()
count = music_file.gets().to_i()
track = music_file
index = 0
while (index < count)
track = read_track(music_file)
tracks << track
index += 1
end
return tracks
end
end
after album = Album.new(album_title, album_artist, album_genre, tracks), I passed the album to a different procedure print_tracks(album), and in print_tracks(album), I have puts album.tracks.
But instead of printing out several lines of track names and track locations, I get something that looks like this:
#<Track:0x000055c028027b08>
#<Track:0x000055c0280277c0>
#<Track:0x000055c028027630>
How do I print out the actual words on the file?
What you are getting in return are instances of your Track class. Each of those instances has access to attributes like name and location as specified under the class definition in attr_accessor. You can change your last statement (return tracks) (take note that return here is not needed since its the last statement in the method, the last thing will be returned by default in ruby).
Try this instead of return tracks
tracks.map{ |track| {track_name: track.name, track_location: track.location} }
This was you will end up with array of hashes with keys of track_name and track_location each containing a value of one track. I am not sure what kind of format you want to return, but this is a rather simple, yet flexible. The most simplistic way would be array of array, which you can get using:
racks.map{ |track| [track.name, track.location] }
You're observing the default behavior defined in Object#to_s and Object#inspect.
Ruby uses the to_s method to convert objects to strings and the inspect method to obtain string representations of objects suitable for debugging. By default, to_s and inspect are more or less the same thing. The only difference is inspect will also show the instance variables.
You can and should override these methods in your Track class. For example:
class Track
def to_s
"#{self.class.name} #{name} # {location}"
end
def inspect
"#<#{to_s}>"
end
end
track.to_s
puts track
# Track: name # /music/name.flac
track.inspect
p track
# #<Track: name # /music/name.flac>
I have tried at least 5 different ways to do it, currently using the .each method.
I believe the problem lies in the print_songs method at the bottom of the code block.
The error I'm getting:
Artist #print_songs lists all of the artist's songs
Failure/Error: expect{artist.print_songs}.to output("Dirty Diana\nBillie Jean\n").to_stdout
expected block to output "Dirty Diana\nBillie Jean\n" to stdout, but output "#<Song:0x000000019757b0>\n#<Song:0x000000019756e8>\n"
Diff:
## -1,3 +1,3 ##
-Dirty Diana
-Billie Jean
+#<Song:0x000000019757b0>
+#<Song:0x000000019756e8>
The code:
class Artist
attr_accessor :name, :song
##all = []
def initialize(name)
#name = name
#songs = []
end
def add_song(song)
#songs << song
end
def songs
#songs
end
def self.all
##all
end
def save
self.class.all << self
end
def self.create_by_name(name)
artist = Artist.new(name)
end
def self.find_or_create_by_name(name)
artist_name = ##all.detect{|x| x.name == name}
if artist_name == nil
self.create_by_name(name)
else
artist_name
end
end
def print_songs
#songs.each{|song| puts song}
end
end
Song Class:
class Song
attr_accessor :name, :artist
def initialize(name)
#name = name
end
# def artist=(name)
# self.artist = Artist.new(name)
# end
def self.new_by_filename(file_name)
file_name.basename("")
end
end
Answer:
def print_songs
#songs.each{|song| puts song.name}
end
It's apparent that the song is probably just not a string, but an object of some sort. Add a to_s method to whatever object that is and puts should automatically call that, although you could, of course, also call to_s manually.
Here's the quick test I did to confirm this behaviour
irb(main):001:0> class Song
irb(main):002:1> def initialize(title)
irb(main):003:2> #title = title
irb(main):004:2> end
irb(main):005:1> end
=> :initialize
irb(main):006:0> s = Song.new "scarborough fair"
=> #<Song:0x0000000030bb78 #title="scarborough fair">
irb(main):007:0> puts s
#<Song:0x0000000030bb78>
=> nil
irb(main):008:0> class Song
irb(main):009:1> def to_s
irb(main):010:2> return #title
irb(main):011:2> end
irb(main):012:1> end
=> :to_s
irb(main):013:0> puts s
scarborough fair
=> nil
irb(main):014:0>
EDIT:
But why is this?
In short, when you create some custom object class, like Song in my example above, Ruby has no idea how to represent it as a string. The default to_s method simply outputs the class and the object ID, which is OK for debugging, but if there's some obvious way to represent the object as a string, like in the case of Song (one would expect song.to_s to return the song title), one has to override the default to_s method or include / inherit from another class/module that has a more fitting implementation of to_s.
It is working as expected.Lets look at tried.Could you post the test cases you have tried with?
a1 = Artist.create(name: 'Lana del re')
a1.add_song('Young and Beautiful')
a1.add_song('haunted')
a1.print_songs
["Young and Beautiful", "haunted"] #output assuming song as a String object
By default, the call to to_s prints the object's class name and an encoding of the object id like so: "#<Song:0x007f9fd16a0770>". That said, you need to override the to_s method on a Song class:
class Song
def initialize(title)
#title = title
end
def to_s
#title
end
end
Then you would need to modify the print_songs method accordingly on an existing Artist class:
def print_songs
puts #songs.each(&:to_s)
end
The each(&:to_s) bit basically invokes the to_s method on each Song object passed to the block, which is essentially the same as
def print_songs
puts #songs.each { |song| song.to_s }
end
This could've also been rewritten as just
def print_songs
puts #songs
end
and in this case puts would implicitly invoke the to_s method on the elements of #songs.
I am pretty new to programming and need some help/feedback on my code.
My goal is to scrape my data, which is working fine, and then display that data to my user in a numbered list. I am simply having difficulty displaying this data. I do not get any errors back my program simply skips my method altogether. Thanks in advance for any help/feedback!
class BestPlaces::Places
attr_accessor :name, :population, :places
##places = []
def self.list_places
# puts "this is inside list places"
self.scrape_places
end
def self.scrape_places
doc = Nokogiri::HTML(open("https://nomadlist.com/best-cities-to-live"))
places = doc.search("div.text h2.itemName").text
rank = doc.search("div.rank").text
places.collect{|e| e.text.strip}
puts "you are now in title"
##places << self.scrape_places
puts "#{rank}. #{places}"
end
end
end
CLI Page:
class BestPlaces::CLI
def list_places
puts "Welcome to the best places on Earth!"
puts #places = BestPlaces::Places.list_places
end
def call
list_places
menu
goodbye
end
end
There are a few things that could be addressed in this code, but let's first see a reworking:
require 'nokogiri'
require 'open-uri'
module BestPlaces
class Places
attr_accessor :name, :population, :places
def initialize
#places = []
end
def scrape_places
doc = Nokogiri::HTML(open("https://nomadlist.com/best-cities-to-live"))
places = doc.search("div.text h2.itemName")
ranks = doc.search("div.rank")
places.each{|e| #places << e.text.strip}
puts "you are now in title"
#places.each do |place|
i = #places.index(place)
puts "#{ranks[i].text}. #{place}"
end
end
end
class CLI
def list_places
puts "Welcome to the best places on Earth!"
BestPlaces::Places.scrape_places
end
def call
list_places
menu
goodbye
end
end
end
You have what looks to be an incomplete Module/Class setup. One can call the above like so:
bp = BestPlaces::Places.new
bp.scrape_places
The ##places variable was unnecessary, we can use #places instead to hold values that need to be accessed within the Places class. Also, nokogiri returns a string object when using the .text method on search results, which means you cannot iterate over them like an array. I hope this helps.
I'm trying to subclass Array to implement a map method that returns instances of my Record class. I'm trying to create a sort of "lazy" array that only instantiates objects as they are needed to try and avoid allocating too many Ruby objects at once. I'm hoping to make better use of the garbage collector by only instantiating an object on each iteration.
class LazyArray < Array
def initialize(results)
#results = results
end
def map(&block)
record = Record.new(#results[i]) # how to get each item from #results for each iteration?
# how do I pass the record instance to the block for each iteration?
end
end
simple_array = [{name: 'foo'}, {name: 'bar'}]
lazy_array_instance = LazyArray.new(simple_array)
expect(lazy_array_instance).to be_an Array
expect(lazy_array_instance).to respond_to :map
lazy_array_instance.map do |record|
expect(record).to be_a Record
end
How can I subclass Array so that I can return an instance of my Record class in each iteration?
From what I know, you shouldn't have to do anything like this at all. Using .lazy you can perform lazy evaluation of arrays:
simple_array_of_results.lazy.map do |record|
# do something with Record instance
end
Now, you've got some odd situation where you're doing something like -
SomeOperation(simple_array_of_results)
and either you want SomeOperation to do it's thing lazily, or you want the output to be something lazy -
lazily_transformed_array_of_results = SomeOperation(simple_array_of_results)
page_of_results = lazily_transformed_array_of_results.take(10)
If that sounds right... I'd expect it to be as simple as:
SomeOperation(simple_array_of_results.lazy)
Does that work? array.lazy returns an object that responds to map, after all...
Edit:
...after reading your question again, it seems like what you actually want is something like:
SomeOperation(simple_array_of_results.lazy.collect{|r| SomeTransform(r)})
SomeTransform is whatever you're thinking of that takes that initial data and uses it to create your objects ("as needed" becoming "one at a time"). SomeOperation is whatever it is that needs to be passed something that responds to map.
So you have an array of simple attributes or some such and you want to instantiate an object before calling the map block. Sort of pre-processing on a value-by-value basis.
class Record
attr_accessor :name
def initialize(params={})
self.name = params[:name]
end
end
require 'delegate'
class MapEnhanced < SimpleDelegator
def map(&block)
#delegate_ds_obj.map do |attributes|
object = Record.new(attributes)
block.call(object)
end
end
end
array = MapEnhanced.new([{name: 'Joe'}, {name: 'Pete'}])
array.map {|record| record.name }
=> ["Joe" "Pete"]
An alternative (which will allow you to keep object.is_a? Array)
class MapEnhanced < Array
alias_method :old_map, :map
def map(&block)
old_map do |attributes|
object = Record.new(attributes)
block.call(object)
end
end
end
I am by no means an expert, and I've run into a little snag when handling objects via a Readline input.
I have a Player class, an Inventory class, and an Item class, and I want the player to be able to type "wear brick" and have it match an Item.name within the array Inventory.contents and add that item to Player.worn. Here's what I have:
class Player
def wear(item)
#worn << item
end
end
class Inventory
attr_accessor :contents
def initialize
#contents = []
#stick = Item.new('a brown stick', 'long and pointy')
#brick = Item.new('a red brick', 'rough and heavy')
#contents << #stick
#contents << #brick
end
def list_contents
#contents.each {|item| puts item.name }
nil
end
end
class Item
attr_accessor :name, :desc
def initialize(name, desc)
#name = name
#desc = desc
end
end
player = Player.new
inv = Inventory.new
I have a Readline prompt to accept the first token of an input string as a command, here 'wear' as a case, but I'm having a hard time grasping how to match the subsequent string within a object inside an array of objects with one word.
inv.contents.inspect:
[#<Item:0x007fcf61935bb0 #name="a brown stick", #desc="long and pointy">, #<Item:0x007fcf61935b38 #name="a red brick", #desc="rough and heavy">]
How could I have "wear brick" search through the Array inv.contents to match #name="a red brick" and select that item to input into Player.wear?
#c650 : thank you. that looks to have solved it!
New Class:
class Player
def initialize
#inventory = Inventory.new
#worn = []
#input = "brick"
end
def wear(keyword)
#inventory.contents.map{|x| #worn << x and #inventory.contents.delete(x) if x.name.include?(keyword) }
end
end