变量的基本问题

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正在用“hand = newgame”进行修改。查看p1“。我甚至不知道为什么P1会被修改，所以我在这里完全困惑。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

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 2

您已经定义了一个方法view这需要一个参数hand（顺便说一句，括号都不错，不知道为什么你总是忽略它们在你的代码，即使是在方法签名）。 view方法修改其参数hand。你把它作为

hand = newgame.view p1 

这p1由法view修改，这就是为什么它的变化。

我也很好奇你为什么设置p1到0 ...然后将其设置为一个数组数组。没有理由这样做。此外，尝试使用描述性变量名称，以及其他人。

Answer 3

FWIW，你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 

此版本不修改任何东西，所以避免了这个问题。