[英]How do I deep copy a Proc in Ruby?
Is there a straightforward way in Ruby to produce a copy of a Proc? Ruby中有一种简单的方法可以生成Proc的副本吗?
I have a Proc called @foo
. 我有一个叫做
@foo
的Proc。 I want another method to periodically augment @foo with additional logic. 我想要另一种方法来定期用额外的逻辑来增加@foo。 For example:
例如:
# create initial Proc
@foo = lambda { |x| x }
# augment with more logic
@foo = lambda { |x| x > 1 ? x*x : @foo[x] }
I don't want the second line that does the augmentation to produce a recursive function. 我不希望进行扩充的第二行产生递归函数。 Instead, I want @foo to be bound by value into the lexical scope of the new @foo definition, producing a function that looks more like this:
相反,我希望@foo被值绑定到新的@foo定义的词法范围,产生一个看起来更像这样的函数:
@foo = lambda { |x| x > 1 ? x*x : lambda{ |x| x }[x] }
I get an infinite recursion and an eventual stack overflow instead, due to the resulting function looking like this: 我得到一个无限递归和最终的堆栈溢出,因为结果函数看起来像这样:
@foo = lambda { |x| x > 1 ? x*x : lambda { |x| x > 1 ? x*x : { lambda |x| # etc...
I'd like the code to be like this: 我希望代码是这样的:
# augment with more logic
@foo = lambda { |x| x > 1 ? x*x : (@foo.clone)[x] }
but clone doesn't work on Procs. 但克隆不适用于Procs。
Additionally, the standard Ruby deep copy hack, using marshal and unmarshal, doesn't work on Procs either. 此外,使用marshal和unmarshal的标准Ruby深度复制hack也不适用于Procs。 Is there some way to do this?
有办法做到这一点吗?
Even if clone
would work on Proc
s, it wouldn't help you, because you'd still be calling clone
on the new value of @foo
, not on the previous one like you want. 即使
clone
可以在Proc
,它也无济于事,因为你仍然会在@foo
的新值上调用clone
,而不是像你想要的那样在前一个上调用clone
。
What you can do instead is just store the old value of @foo
in a local variable that the lambda can close over. 你可以做的只是将
@foo
的旧值存储在lambda可以关闭的局部变量中。
Example: 例:
def augment_foo()
old_foo = @foo
@foo = lambda { |x| x > 1 ? x*x : old_foo[x] }
end
This way old_foo
will refer to the value that @foo
had when augment_foo
was called and everything will work as you want. 这样
old_foo
将引用augment_foo
在调用@foo
具有的值,并且一切都将按您的意愿工作。
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