阻止范围在红宝石

我的理解是,ruby块具有块范围,并且块内创建的所有变量将仅在块内生效.

示例：

food = ['toast','cheese','wine']
 food.each { |food| puts food.capitalize}
 puts food

输出：

"Toast"
"Cheese"
"Wine"
"Wine"

如果你把块里的食物变量(每个块),我的理解是它有阻止的范围.它只在封闭范围内,对外在的可变食物没有任何影响.

但是行为是不同的,在这种情况下修改了名为food的外部变量.这个理解是否正确,在红宝石中我们有阻挡范围吗？

解决方法

这是ruby 1.8的预期行为. It was fixed in 1.9.以下的代码片段以红宝石1.9.3运行

food = ['toast','wine']
food.each { |food| puts food.capitalize.inspect} # !> shadowing outer local variable - food
puts food.inspect
# >> "Toast"
# >> "Cheese"
# >> "Wine"
# >> ["toast","cheese","wine"]

你是正确的,从块的食物被限定到该块,并用这个名字影响其他变量.但是如果你做了一些破坏性的东西,它将被反映在原始的数组中,因为它是引用数组元素而不是它的副本.注意：

food = ['toast','wine']

food.each { |f| f.capitalize} # transform and discard
food # => ["toast","wine"]

food.each { |f| f.capitalize! } # transform destructively (bang-version)
food # => ["Toast","Cheese","Wine"]