From: "Stephan Kämper" <stephan.kaemper@...>
Date: 2007-11-02T17:20:27+09:00
Subject: Re: What the hell is the => operator?

 
Am Freitag, den 02. November 2007 um 09.06 Uhr schrieb Just Another Victim of the Ambient Morality <ihatespam@hotmail.com>:

>    I've seen this in some ruby code but I have no idea what is going on. 
>I'd do a google search on it but... I don't search for '=>' and I don't know 
>how to describe it in english so that the context will be this!
>    I've seen this operator used in, what seems to me, to be totally bizarre 
>contexts.  As far as I know, it's only used in hash definitions.  However, 
>it's used in both Rails and scRUBYt.  It looks something like this:
>
>
>method_call :symbol => false do
>    # do something here
>end
>
>another_method  random_var, :symbol => :other_symbol do
>    # do something else
>end
>
>
>    Can someone explain to me what is going on here?

It's mostly 'syntactic sugar'. In Ruby you can leave the curly braces {} in a method call away in case the last values form a hash.

For example:

method_call( param_1, param_2, :sym1 => 'something', 'another_key' => :another_value )

Note that you're not limited to symbols as hash keys.


The following examples are esentially the same:

method_call( :symbol => false ) do
    # do something here
end

another_method( random_var, :symbol => :other_symbol ) do
    # do something else
end


method_call( { :symbol => false } ) do
    # do something here
end

another_method( random_var, { :symbol => :other_symbol } ) do
    # do something else
end



'=>' is used to point from a hash key to its value. 



Happy rubying

Stephan