Rails验证:if => Proc.new还是lambda? [英] Rails validation :if => Proc.new or lambda?

问题描述

我发现在验证方法的:if选项中看到的所有示例(包括rails文档)中，例如都使用Proc.new而不是lambda

I have found that in all examples (include rails documentation) that I have seen for the :if option of validation methods uses Proc.new instead of lambda, for example

class Foo < ActiveRecord::Base
  validates_presence_of :name, :if => Proc.new{|f| .... } # why not lambda here?
end

有什么原因吗? 据我所知lambda

is there any reason for this? As far as I know, lambda

1. 对参数的要求更严格.
2. lambda块中的return语句也从该块返回，而不是从调用函数返回.

对于上述:if选项，这似乎都是合乎需要的行为，我有什么想念的吗?

Both seems to be desirable behavior for :if option mentioned above, is there anything I am missing?

推荐答案

对于上述:if选项，这似乎都是合乎需要的行为，我有什么想念的吗?

Both seems to be desirable behavior for :if option mentioned above, is there anything I am missing?

我猜是:

允许Procs更为可取，因为它们不关心参数的数量.因此，我可以轻松编写以下任何内容:

It's more desirable to allow Procs as they don't care about the number of arguments. So I could easily write any of the below:

validates_presence_of :name, :if => Proc.new{|f| f.display_name.blank? }    # I care about 'f' here as I need it to check something.

...和:

validates_presence_of :secret_sauce, :if => Proc.new{ MyApp::REQUIRE_SECRET_SAUCE }    # I don't care about any arguments being passed in.

这似乎是一件小事，但我想它增加了灵活性.

This may seem like a minor thing, but I guess it adds to the flexibility.

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