Question

I feel like I’m missing something very, very fundamental, so, to avoid tearing out more hair, I come here to ask why p1, p1t and p1t2 are getting modified on with “hand = newgame.view p1”. I don’t even know why p1 is getting modified, so yeah I’m totally baffled here. Any help would be tremendously appreciated.

# encoding: utf-8

class Cards

def view hand
    x = 0
    hand.each do |card|
        if card[0] == 's'
            card[0] = '♠'
        elsif card[0] == 'd'
            card[0] = '♦'
        elsif card[0] == 'h'
            card[0] = '♥'
        elsif card[0] == 'c'
            card[0] = '♣'
        else
            #nil
        end
        hand[x] = card
        x = x + 1
    end
    prettyhand = ''
    hand.each do |card|
        prettyhand = prettyhand + card[0] + card[1] + ' '
    end
    return prettyhand
end#view

end#Cards
###########

deck = 0
up = 0
p1 = 0
p2 = 0
newgame = Cards.new
p1 = [["c", "4"], ["s", "4"], ["d", "q"], ["c", "8"], ["s", "5"], ["s", "q"], ["h", "3"], ["c", "10"]]
    p1t = []
    p1t2 = []
    hand = ''
    p1.each do |card|
        p1t.push card
    end
    p1t.each do |card|
        p1t2.push card
    end
    p '----------------------------------'
    p 'fresh p1:'
    p p1
    p p1t
    p p1t2
    hand = newgame.view p1
    p 'unfresh p1:'#why is this changing??
    p p1
    p p1t
    p p1t2
    p '----------------------------------'

output:

"----------------------------------"
"fresh p1:"
[["c", "4"], ["s", "4"], ["d", "q"], ["c", "8"], ["s", "5"], ["s", "q"], ["h", "3"], ["c", "10"]]
[["c", "4"], ["s", "4"], ["d", "q"], ["c", "8"], ["s", "5"], ["s", "q"], ["h", "3"], ["c", "10"]]
[["c", "4"], ["s", "4"], ["d", "q"], ["c", "8"], ["s", "5"], ["s", "q"], ["h", "3"], ["c", "10"]]
"unfresh p1:"
[["♣", "4"], ["♠", "4"], ["♦", "q"], ["♣", "8"], ["♠", "5"], ["♠", "q"], ["♥", "3"], ["♣", "10"]]
[["♣", "4"], ["♠", "4"], ["♦", "q"], ["♣", "8"], ["♠", "5"], ["♠", "q"], ["♥", "3"], ["♣", "10"]]
[["♣", "4"], ["♠", "4"], ["♦", "q"], ["♣", "8"], ["♠", "5"], ["♠", "q"], ["♥", "3"], ["♣", "10"]]
"----------------------------------"

Answer 1

Arrays are passed by reference, not copied. Check out this snippet.

a1 = [[1], [2], [3]]
a2 = []

a2 << a1.first # push a reference to the array
a2 # => [[1]]


a1[0][0] += 1 # => 2
a1 # => [[2], [2], [3]] # a1 has changed
a2 # => [[2]] # a2 changed too!

# now push a copy of the array
a2 = [a1.first.dup] # => [[2]]

a1[0][0] += 1 # => 3
a1 # => [[3], [2], [3]] # a1 has changed
a2 # => [[2]] # a2 has not