尽早突破起点/终点

Question

我想要一种退出Begin / End块的方法，同时仍将其结果分配给的变量赋值。

def foo
  @foo ||= begin
    puts "running"

    return "leaving early" if true # would be some sort of calculation

    # Other calculations
  end
end

我希望发生什么

> foo
running
=> leaving early
> foo
=> leaving early

实际发生了什么

> foo
running
=> leaving early
> foo
running
=> leaving early

该代码不起作用，因为return没有设置就退出了整个方法@foo。使用break或next仅循环工作。开始中是否有任何事情可以阻止我的思维方式？

目前可以做到的方式，但我希望避免：

• 在begin块内分配变量并返回
• 将begin块的其余部分放在if语句中
• 在开始块之前执行计算

关于突破规则，似乎有很多相关问题，但我找不到一个能回答这个特定版本的问题（也许是因为这不可能）。

Answer 1

I think you're going to save yourself a whole heck of a lot of strife if you just put all that logic into its own method:

def foo
  @foo ||= compute_foo
end

def compute_foo
  puts "running"

  return "leaving early" if true # would be some sort of calculation

  # Other calculations
end

This decouples the computation from the memoization, making it easier to test and reason about, and it's a fairly common design pattern in Ruby and other languages.

Of course, there are ways of doing what you're asking. The most obvious solution being an immediately-invoked anonymous proc:

def foo
  @foo ||= (proc do
    puts "running"

    next "leaving early" if true # would be some sort of calculation

    # Other calculations
  end)[] # or .call or .()
end

But you certainly wouldn't be doing yourself or any future maintainers of this code any favors.