From: Siddharth Reddy <sid.waste@...>
Date: 2011-09-29T03:23:51+09:00
Subject: Re: Ruby Syntax @keywords ||= [ ]

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Awesome ! this should clear my doubts..

On Wed, Sep 28, 2011 at 11:48 PM, Dave Aronson <
rubytalk2dave@davearonson.com> wrote:

> On Wed, Sep 28, 2011 at 13:07, Bhavesh Sharma <sharmabhavesh@gmail.com>
> wrote:
>
> > Sorry if this comes across as a dumb question, but what does the
> > following syntax mean in ruby.
> >
> > @keywords ||= []
> >
> > I understand that its setting the instance variable as an array but what
> > is the logical operator '||' doing in there.
>
> "x ||= y" is a common idiom for "if x is nil, set it to y".
>
> An operator followed by the = sign is like saying "use the thing on
> the left, as the left side of the operator".  In other words, the
> above is equal to:
>
>  @keywords = @keywords || []
>
> Similarly, "x += 1" is equal to "x = x + 1", and so on for all other
> operators.
>
> The || operator specifically won't bother evaluating its right-side
> operator, if the left is true.  In Ruby, two things are not true:
> false, and nil.  So, if the thing on the left is nil (or boolean
> false), it gets the value on the right, else it gets left alone.
>
> -Dave
>
> --
> LOOKING FOR WORK, preferably Ruby on Rails, in NoVa/DC; see main web site.
> Main Web Site: davearonson.com
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>
>

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