提问人：poeticider 提问时间：4/19/2023 最后编辑：Stefanpoeticider 更新时间：4/20/2023 访问量：62
Ruby 嵌套 .each 块中的某些数组元素变为 nil
Ruby some array elements in nested .each block become nil
问：
我希望每个数组元素相互交互。但是，我的代码中的某些元素具有意外的值。nil
如何避免这种不良行为？
下面是组合元素的代码：（它只是打印成对）
def remove_sum_of_zero(arr)
arr.each do |n|
arr.each do |x|
unless arr.index(n) == arr.index(x)
puts "#{arr[n]} is being checked with #{arr[x]}"
end
end
end
end
numArr = [3, 4, -7, 5, -6, 6]
remove_sum_of_zero(numArr)
输出：
5 is being checked with -6
5 is being checked with
5 is being checked with 6
5 is being checked with 3
5 is being checked with
-6 is being checked with 5
-6 is being checked with
-6 is being checked with 6
-6 is being checked with 3
-6 is being checked with
is being checked with 5
is being checked with -6
is being checked with 6
is being checked with 3
is being checked with
6 is being checked with 5
6 is being checked with -6
6 is being checked with
6 is being checked with 3
6 is being checked with
3 is being checked with 5
3 is being checked with -6
3 is being checked with
3 is being checked with 6
3 is being checked with
is being checked with 5
is being checked with -6
is being checked with
is being checked with 6
is being checked with 3
我尝试使用不同的数组，每次不同的值变成.nil
答：
4赞
Stefan
4/19/2023
#1
each产生元素，而不是它们的索引，即 变为 、 、 等。将该值作为索引传递没有多大意义。n34-75arr[n]
如果你好奇数组索引在 Ruby 中是如何工作的——负索引从数组的末尾算作最后一个元素：-1
numArr = [ 3, 4, -7, 5, -6, 6]
# 0 1 2 3 4 5 6 ... ← positive indices (and 0)
# ... -7 -6 -5 -4 -3 -2 -1 ← negative indices
如果你需要元素及其索引，each_with_index可以同时生成两个值：
def remove_sum_of_zero(arr)
arr.each_with_index do |a, i|
arr.each_with_index do |b, j|
next if i == j
puts "#{a} is being checked with #{b}"
end
end
end
或者您可以使用可以产生所有对的排列：（即与上述相同）
def remove_sum_of_zero(arr)
arr.permutation(2) do |a, b|
puts "#{a} is being checked with #{b}"
end
end
或者，如果 compare to 等同于 compare to（即，如果元素的顺序无关紧要），您可能需要省略这些“重复项”的组合：abba
def remove_sum_of_zero(arr)
arr.combination(2) do |a, b|
puts "#{a} is being checked with #{b}"
end
end
评论