Turn Ruby array into strings - problem with my code? - ruby

Question

I want to turn this array of cards into a string (output I want is at the bottom) Here's my code:
# Returns an array of 5 cards in player's hand:
# => Eg: ['6♠', '3♦', 'A♣', 'J♦', 'J♥']
private
def cards
%w(6♠ 3♦ A♣ J♦ J♥)
end
def to_s
cards.map {|card| "-" + card.to_s}.join("-")
end
end
The output I want is a string of the cards like this: - 6♠ - 3♦ - A♣ - J♦ - J♥ -

Answer 1

As the question is currently posed, you have 3 things going wrong:
First, you're trying to create private methods without first calling a class. This also explains the extra end. To fix that, we can add the class call at the beginning like so:
class Test
private
def cards
%w(6♠ 3♦ A♣ J♦ J♥)
end
def to_s
cards.map {|card| "-" + card.to_s}.join("-")
end
end
Second, we need to actually use the class somehow. We can use Class.new for this, like so:
class Test
private
def cards
%w(6♠ 3♦ A♣ J♦ J♥)
end
def to_s
cards.map {|card| "-" + card.to_s}.join("-")
end
end
puts Test.new
#=> "-6♠--3♦--A♣--J♦--J♥"
I can only assume your posted code section was just incomplete, that you weren't having issues with the first couple things, and that you're just having problems with the formatting in that output line. If so, there are many different ways to do this, but your main issue is the following section of your code:
"-" + card.to_s}.join("-")
You are iterating over the array and adding a "-" before every element. You are then joining up those elements with a redundant "-" to create your string. You need to get rid of one or the other. I suggest just getting rid of the latter like so:
cards.map {|card| "-" + card.to_s}.join
Its also worth noting that your array elements are already strings, so the .to_s is unnecessary. Your line could therefore be reduced to:
cards.map {|card| "-" + card}.join
This will result in #=> "-6♠-3♦-A♣-J♦-J♥"
The only thing missing now is that last dash. To fix that, we just add the dash independently at the end of your newly joined array like so:
cards.map {|card| "-" + card}.join + "-"
The completed test would then look like this:
class Test
private
def cards
%w(6♠ 3♦ A♣ J♦ J♥)
end
def to_s
cards.map {|card| "-" + card}.join + "-"
end
end
puts Test.new
#=> "-6♠-3♦-A♣-J♦-J♥-"
At the end of the day though, your string formatting issues could essentially be addressed by just replacing ("-") with +"-"

Answer 2

Join with Format String
From inside a class, you can do this fairly easily with a combination of cards.join and a format string. For example:
def cards
%w(6♠ 3♦ A♣ J♦ J♥)
end
def to_s
sprintf "- %s -", cards.join(" - ")
end
You can test this in irb outside of a class by defining your #cards method, and then invoking Kernel#sprintf with the format string and the String formed by joining your cards as arguments.
sprintf "- %s -", cards.join(" - ")
#=> "- 6♠ - 3♦ - A♣ - J♦ - J♥ -"
There are other interpolation methods available as well, such as Kernel#format, embedded expressions, and %-style interpolation expressions, but this seems both simple and well-supported with any reasonably recent Ruby version.