From: "s.ross" <cwdinfo@...>
Date: 2008-02-20T07:43:38+09:00
Subject: Re: ||= [] idiom

If you don't mind being really cryptic about it:

@categories = resource.inject({}) {|a, v| (a[v.tag] ||= []) << v; a}

I think this works, but I'm not sure the "next guy" would ever figure  
out what it does :)

On Feb 19, 2008, at 2:11 PM, Leslie Viljoen wrote:

> I often make use of this idiom to add something to an array in a  
> hash of arrays:
>
> @categories = {}
>
> pagelist.each do |resource|
>    @categories[resource.tag] ||= []
>    @categories[resource.tag] << resource
> end
>
>
> .. is there a better way? Can the two @categories lines
> be made into one?
>
>
> Les

If you don't mind being really cryptic about it:

@categories = resource.inject({}) {|a, v| (a[v.tag] ||= []) << v; a}

I think this works, but I'm not sure the "next guy" would ever figure  
out what it does :)