什么是“针对"?在Ruby中 [英] What is "for" in Ruby

问题描述

在Ruby中:

for i in A do
    # some code
end

与:

A.each do |i|
   # some code
end

for不是内核方法:

• 红宝石中的"for"到底是什么
• 是否可以使用其他关键字来做类似的事情?

• What exactly is "for" in ruby
• Is there a way to use other keywords to do similar things?

类似的东西:

 total = sum i in I {x[i]}

映射到:

 total = I.sum {|i] x[i]}

推荐答案

几乎是语法糖.一个区别是，虽然for将使用其周围的代码范围，但each在其块内创建一个单独的范围.比较以下内容:

It's almost syntax sugar. One difference is that, while for would use the scope of the code around it, each creates a separate scope within its block. Compare the following:

for i in (1..3)
  x = i
end
p x # => 3

与

(1..3).each do |i|
  x = i
end
p x # => undefined local variable or method `x' for main:Object

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