Ruby保护块内的外部变量[重复]答案

【问题标题】：Ruby protect outer variable inside block [duplicate]Ruby保护块内的外部变量[重复]
【发布时间】：2014-07-13 13:17:28
【问题描述】：

假设有方法：

def in_block
  x = "This variables outer block"
  3.times do |i|
    x = i
    puts "x inside block - #{x}"
  end
  puts x
end
in_block

# >> x inside block - 0
# >> x inside block - 1
# >> x inside block - 2
# >> 2

如何保护我的x 变量？

【问题讨论】：

标签： ruby block

【解决方案1】：

用分号;分隔块中的参数，这表明该块需要自己的x，与已经在块外创建的任何x无关。

def in_block
  x = "This variables outer block"
  3.times do |i; x|
    x = i
    puts "x inside block - #{x}"
  end
  puts x
end
in_block

# >> x inside block - 0
# >> x inside block - 1
# >> x inside block - 2
# >> This variables outer block

但是简单的, 怎么样？这是不一样的。看那个块有两个参数的例子：

def in_block
  #x = "This variables outer block"
  [1,2,3,4].each_with_index do |i; x|
  puts x.class
    x = i
    puts "x inside block - #{x}"
  end
  #puts x
end

in_block # => [1, 2, 3, 4]

# >> NilClass
# >> x inside block - 1
# >> NilClass
# >> x inside block - 2
# >> NilClass
# >> x inside block - 3
# >> NilClass
# >> x inside block - 4

和,:

def in_block
  #x = "This variables outer block"
  [1,2,3,4].each_with_index do |i, x|
  puts x.class
    x = i
    puts "x inside block - #{x}"
  end
  #puts x
end

in_block # => [1, 2, 3, 4]

# >> Fixnum
# >> x inside block - 1
# >> Fixnum
# >> x inside block - 2
# >> Fixnum
# >> x inside block - 3
# >> Fixnum
# >> x inside block - 4

【讨论】：