Question

我觉得我错过了非常非常基本的东西，所以，为了避免撕掉更多的头发，我来这里问为什么p1，p1t和p1t2被修改为“hand = newgame.view p1”。我甚至不知道为什么p1会被修改，所以是的，我在这里完全不知所措。任何帮助将非常感激。

# 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 '----------------------------------'

输出：

"----------------------------------"
"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

你已经定义了一个方法view，它接受一个参数hand（顺便说一句，parens很好，不知道为什么你总是在代码中省略它们，即使在方法签名中也是如此）。 view方法修改其参数hand。你把它称为

hand = newgame.view p1

此p1由方法view修改，这就是它发生变化的原因。

我也很好奇为什么要将p1设置为0 ...然后将其设置为数组数组。没有理由这样做。此外，尝试为自己和他人使用描述性变量名称。

Answer 2

数组通过引用传递，而不是复制。看看这个片段。

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

Answer 3

FWIW，您的view方法可以简化很多：

class Cards
  Suits = { 'c' => '♣', 'd' => '♦', 'h' => '♥', 's' => '♠' }

 def view(hand)
    hand.map do |suit, rank| [ Suits[suit], rank ] end
 end
end

此版本不会修改任何内容，因此可以避免此问题。

变量的基本问题

3 个答案: