From: "David A. Black" <dblack@...>
Date: 2008-08-13T01:16:56+09:00
Subject: Re: What's the easiest way to check if param[:x][:y] exists?

Hi --

On Wed, 13 Aug 2008, Joshua Muheim wrote:

> Hi all
>
> In PHP I can simply check whether $param['x']['y'] exists regardless
> whether $param['x'] exists or not.
> In Rails I get a NoMethodError when using
>
> if param[:x][:y]
>  ..
> end
>
> when param[:x] is nil. So I always have to use
>
> if param[:x] and param[:x][:y]
>  ..
> end
>
> but I think that's not very beautiful - think about a case where I have
> to check whether param[:a][:b][:c][:d][:...] exists or not!
>
> Maybe there's a cooler way to do this? ;-)

Yes: design your data structures with classes and modules and methods,
instead of quintuply-nested hashes :-) But if you want to have a hash
that automatically inserts a hash for an unknown key, you can do:

func = lambda {|h,k| h[k] = Hash.new(&func) }
hash = Hash.new(&func)

I think that's the OK version.... You can also rescue NoMethodError,
though that's kind of fuzzy with lots of nesting.


David

-- 
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