From: "Matthew K. Williams" <matt@...>
Date: 2010-04-08T02:04:16+09:00
Subject: Re: Manipulating of an Array of Structs

On Thu, 8 Apr 2010, Anthony Wright wrote:

> I have data that I've extracted from a database, that I wish to pass to
> a calling (external) piece of software through Drb.
>
> The are a large number of data set formats, but an employee based
> example might look something like:
>
> ID     Name                 Age
> 1     Mary Smith           23
> 3     Frank Zappa          52
> 19     Mary Jones           41
>
> I'm trying to find a "nice" structure to pass this data around in, so
> that it can be easily understood and manipulated.
>
>
>
>
> I'm currently using an Array of Hashes so it looks something like:
>
> [ { :id => 1, :name => "Mary Smith", :age => 23 }, { :id => 3, :name =>
> "Frank Zappa", :age => 52 }, { :id =>19, :name => "Mary Jones", :age =>
> 41 } ]
>
> or more nicely formatted
>
> [
> 	{ :id => 1, :name => "Mary Smith",  :age => 23 },
> 	{ :id => 3, :name => "Frank Zappa", :age => 52 },
> 	{ :id =>19, :name => "Mary Jones",  :age => 41 }
> ]
>
>
>
> This is fine if I want to extract single pieces of information, but it's
> clumsy to manipulate the whole array, for example, extract out all the
> names, sort the array by age, create a new array containing employees
> over 40. It's also inefficient as I'm repeating the labels on every record.
>
> I realise I can do this by writing block code to process the array, but
> I feel there must be a cleaner way to store and manipulate data of this
> form in ruby.  Something on the lines of Struct would be great to remove
> the excessing labels, but Struct doesn't help with the array manipulation.
>

Take a gander at Dr Nic's map_by_method gem, it has this functionality -- 
including sort_by, group_by, and index_by

http://drnicwilliams.com/category/ruby/map_by_method/